Idle bouncing up and down after cam install.....someone calm me down!

[jspaeth]

I pulled my head, then put it back together, but with greddy IM, and the car was fine.

Now, I just dropped in HKS step 2 cams this weekend (they are 264/264 12/11.5 mm lift In/Ex)...initially the car idles high due to the coolant being cold, and idles steady however.

Once the car warms up and the idle begins to drop down to around 1200-1300, it starts bouncing back and forth between 800 and 1400, with a period of about one second (fast bouncing, not slow, smooth).

However, once i get the car in gear and drive, it feels fine.


I am 99.99% sure the timing is fine. I have done that before and I checked to make sure the crank didn't turn, mating marks were fine, CAS is fine, etc.

Like I said, up through 5-6K, the car feels fine, the timing doesn't feel off.


Is it normal for the idle to get screwed up like that when swapping to those type of cams?

btw, the car is running of a PowerFC and has previously been tuned with stock cams, so yeah


Also, secondary question;

Does the direction of coolant flow through the IACV matter? I.E.....does it matter which hose gets hooked up to which port on the IACV?

my gut instinct is no, but just wanted to check....

Thanks!

[dongoesby]

I hope I can help. I had a similar problem lately. After my swap, the idle wasn't perfect, it would jump from 500 to 900 every one min. I know there are many reasons that would cause this like vacuum leak or timing. I'm sure you know this.

However, I found mine to be the coolant system. I didn't install the coolant properly and caused air trapping inside, so the temperature sensor (ecu) sends bad signals to the ecu and caused this.

I can't say for sure that yours is the same too, but mine now idle a lot better. And adjust the IAVC would help a little too. If yours happen to be not the case, then I think another problem could be your ECU sending wrong signals. Or a bad temperature sensor would cause this too.

hope this help.

[jspaeth]

Thanks for the help, but the idle is bouncing back and forth between 800-1400 RPM about once every 2 seconds.

Up, down, up, down

Like the same rate at which you go in and out when you are having slow, casual sex.

[dongoesby]

lol at casual sex

yea mine was like that bouncing. It sounded like having difficulty on breathing, and my boost gauge would bounce slightly with it too (vacuum). If you didn't touch your coolant system, my broad guess would be a faulty temperature sensor, or the ecu needs to be reset.

somebody chime in!

[240sxxs]

fuck..what sup with all the SR having trouble at idle and shit...well...i have tomie stage 2 cams..and im having trouble with idle also....when i warm up the car...idle fine..when park idle fine..

[Chrischeezer]

First things first.. check codes on your ECU
that's not normal.. sounds like timing to me but I'm not there.

i had a fully built head, idle perfectly at 900, with a tuned ECU

[fliprayzin240sx]

Welcome to having big cams with lots of over lap. My shit is idling between 1k to almost 2k with Tomei 272 Procams. What makes it worst is that my Fast Idle valve doesnt work for some reason. Only way for my AC to work without killing the engine is 1500 rpm. Even then, it'd still die coming to a stop from time to time.

[2fast4y0u]

mine does the same thing.
hks step, greddy intake manifold, timing is dead on!
once the thermostat opens the idle is fine. i was told it was a IACV going bad. i have another one laying around so it will be going on today. if it fixes the issue, i will let you know.

see i also have a voltage issue, and when my idle drops, my volts drop, causing the car to almost stall.

[fliprayzin240sx]

mine does the same thing.
hks step, greddy intake manifold, timing is dead on!
once the thermostat opens the idle is fine. i was told it was a IACV going bad. i have another one laying around so it will be going on today. if it fixes the issue, i will let you know.

see i also have a voltage issue, and when my idle drops, my volts drop, causing the car to almost stall.

Ofcourse you're voltage will drop...not enough RPMs to spin the alternator!

[jspaeth]

Ray....

Like I said, I am 99% sure timing is good, and BEFORE the cams (just intake manifold) vacuum was at ~20 in Mg

With the cams, at first, car idles high (coolant cold) and SMOOTH at like 1500-1600 RPM, vacuum at ~17 in Mg.

I have read that the vacuum will be weaker due to the cam overlap, so that's good.

Car runs just fine in gear, idles fine when COLD.

As soon as it heats up and the idle begins to come down to target (~1000-1100 RPM), it starts doing the oscillating thing (oscillates like every 1 second!).

I'm hoping that my tuner can smooth this out a bit.

Oil pressure, vacuum, timing, fuel pressure are all okay.

Only thing that has changed is the cam install, and I am 99% sure it was done coorectly, because car runs great, except for idle.


I am stuck......I wouldn't consider this "lumpy" cam idle....it's more like the IACV is causing the revs to overshoot from either direction.....

[GSXRJJordan]

Sounds like you should raise the idle setting, and see it that smooths it out. I'd imagine the PFC has an electronic adjustment for the IACV steppers.

[fliprayzin240sx]

Ray....

Like I said, I am 99% sure timing is good, and BEFORE the cams (just intake manifold) vacuum was at ~20 in Mg

With the cams, at first, car idles high (coolant cold) and SMOOTH at like 1500-1600 RPM, vacuum at ~17 in Mg.

I have read that the vacuum will be weaker due to the cam overlap, so that's good.

Car runs just fine in gear, idles fine when COLD.

As soon as it heats up and the idle begins to come down to target (~1000-1100 RPM), it starts doing the oscillating thing (oscillates like every 1 second!).

I'm hoping that my tuner can smooth this out a bit.

Oil pressure, vacuum, timing, fuel pressure are all okay.

Only thing that has changed is the cam install, and I am 99% sure it was done coorectly, because car runs great, except for idle.


I am stuck......I wouldn't consider this "lumpy" cam idle....it's more like the IACV is causing the revs to overshoot from either direction.....

Its the cams...trust me, I've been dealing with this same issue since I got the car back in Feb. Same shit, idles fine when cold because the car bumps up the idle due to the cold idle function on the TB (thats why coolants runs thru it). Once its off and the cold idle is off, it gets loppy as fuck. I've tried cleaning the IACV, changed it to another known good one, played around with the PFC settings, I've even changed the TB from a Skyline TB to an S14 stock one and then to an NA S14 one, same shit.

[slider2828]

I don't have any of these problems at all. Also PFC with HKS Step 1 264's though.... Could be a lopey idle, but try this trick...

There is a very very small screw near the stopper for the round thing that connects to your throttle cable... turn it in a lot so that even though at idle, the butterfly remains MORE open, then back off the idle by screwing in your IACV....

Turn off your car and wait... see if that helps....

On S13 and S14 Fast Idle is controlled by a stupid piece of wax which melts when coolant passes through it and softens that piece of wax which allows the butterfly plate to close. Its a stupid system.... Adjusting that helps too because my friends S14 was Idling like at 1500 all day, but you can adjust fast idle too... That usually helps a lot too

[johngriff]

Its totally not the cams. Big cams does not make this issue.

More than likely it is air in the coolant system, or an intake leak, or you need to adjust the screw on the iacv, but its not the cams.

[2fast4y0u]

Ofcourse you're voltage will drop...not enough RPMs to spin the alternator!

i know that...but dont you think at 800 rpm the alternator should be working??? im sick of having to rev my car to 1500+ rpm to make the alternator "kick in" and start working. 800 rpm SHOULD be plenty to make the alternator work

[GSXRJJordan]

i know that...but dont you think at 800 rpm the alternator should be working??? im sick of having to rev my car to 1500+ rpm to make the alternator "kick in" and start working. 800 rpm SHOULD be plenty to make the alternator work

Maybe on a domestic V8, not on any 4cyl. Most alternators need 1200-1300rpm in my experience, especially on first startup.

[2fast4y0u]

so are you telling me that everytime you start your car you have to rev it up to have voltage above 11.5? because i never had this problem till recently

[jspaeth]

Its totally not the cams. Big cams does not make this issue.

More than likely it is air in the coolant system, or an intake leak, or you need to adjust the screw on the iacv, but its not the cams.

John, I almost always trust you, but on this one, I have to question you.

It CANNOT be coolant or intake problem, because NONE of that was touched during the cam install.

Before cams, idle fine.......after cams, fast up and down oscillations when car warms up.

I don't think it's timing, as I quadrupled checked the CAS and timing chain before closing that all up.

I think the IACV is essentially underdamped.......it's a simple closed-loop feedback mechanism....

The "gain" is too high, so when the idle gets too high, the correction it gives is too big, causing the idle to drop too low, and when the idle is too low, it gives it too much air, causing it to overshoot.


Like I said, none of this was happening until the cams went in, and that's the only variable.


I may try opening the IACV screw up a bit.....my PFC tells me it's running a little richer than it usually does. Usually I see 0V on my O2 sensor at idle (lean)....but now it is reading 0.6-0.7V.....so, that's rich, relative to before.

Also, I know the trick with the throttle plate screw, but I think that is the final, band-aid solution to this if I can't work it out some other way.....I certainly don't mind if my idle is 1100 or so, but I don't want it permanently at like 1500 either.


EDIT: John, when you say it's not the cams, I see what you are saying.....the cams per se aren't THE problem, but the idle settings and IACV setup that was working before may not work well with the new cams....so in effect, the cams require things to be re-setup.

[fliprayzin240sx]

Its totally not the cams. Big cams does not make this issue.

More than likely it is air in the coolant system, or an intake leak, or you need to adjust the screw on the iacv, but its not the cams.

K, you got me there John...how would air in the coolant cause the car to idle lopy after its warmed up? I can see the intake leak but not the air in the coolant part. :s101:

[jspaeth]

No one answered me yet, but.....

Does the direction of coolant flow through the IACV matter????

The IACV mounts upside down to the Greddy IM, so I didn't really pay attention to which coolant line was which....

My guess was that it doesn't matter.

[jspaeth]

K, you got me there John...how would air in the coolant cause the car to idle lopy after its warmed up? I can see the intake leak but not the air in the coolant part. :s101:


Also, I should add that vacuum is beautiful.

Before cams, it was -500 mmHg (~19.5 in Mg) and now (before it oscillates) it is like -430 mmHg at 1400 RPM......however once it starts bouncing, the vacuum moves alot too, obviously

[keytops]

No, it doesn't matter. It's just a coolant path through the valve to help warm up the car faster. I would raise the idle a bit and see what happens, most of the time changine the cams will require an adjustment of the IAC valve.

[240sxxs]

i have tomie stage 2 procams..and it does the same thing...but when i mess with the iacv screw lol it idle alot smoother now..sometime 1500 but after lik 5 0r 6 sec it goes down to 1k...and it lopping all the time..up and down...it is the cam

[slider2828]

Wait.... S14SR it does matter....

Make sure the coolant through fast idle is correct if on S14 especially and through that crappy Coolant temp sensor... Actually coming to mind I did have this problem. It was coolant flow through the fast idle causing some issue... I had this EXACT same problem on my friends car...

Trust me cars are not meant to idle at 1500, it gets really hot after awhile....

[SILVIA_KIDs14.5]

adjust the screw on your High idle throttle body and you should be good but fyi when you put cams in the car will bounce up and down if you have over lap

[slider2828]

He says its constantly ever 2 secs, now that isn't normal... It lopes with overlap but it isn't systematic...

[240sxxs]

most high end cams like tomie , hks, BC , will have over lap..no matter what..it just the way the cams builded....correct me if im wrong

[slider2828]

most high end cams like tomie , hks, BC , will have over lap..no matter what..it just the way the cams builded....correct me if im wrong

Yeah they will have overlap for sure.... but Ima just saying overlap is not like a systemematic sound in your idle, its goes

bah bah bah blaaah, bah bah blaaah, baah bah bah bah blaaah... its almost random stumbling which that is not what he described... is all I was referring to

[jspaeth]

No, it doesn't matter. It's just a coolant path through the valve to help warm up the car faster. I would raise the idle a bit and see what happens, most of the time changine the cams will require an adjustment of the IAC valve.

This is what I thought

Wait.... S14SR it does matter....

Make sure the coolant through fast idle is correct if on S14 especially and through that crappy Coolant temp sensor... Actually coming to mind I did have this problem. It was coolant flow through the fast idle causing some issue... I had this EXACT same problem on my friends car...

Trust me cars are not meant to idle at 1500, it gets really hot after awhile....

This is an S13 blacktop.....the flow thorugh the coolant temp sensor is stock, the flow through the throttle body is same as stock.

Only possibility is that the coolant is flowing through IACV backwards, but as I thought (and had confirmed), that doesn't matter.

adjust the screw on your High idle throttle body and you should be good but fyi when you put cams in the car will bounce up and down if you have over lap

The cold idle is just fine, and was before the install too. It cold idles starting at like 1500 or so, and works it's way down toward 900-1000. So I think it's more of an IACV issue. If the IACV continues to suck and behave UNSTABLE like this, I may just disconnect the harness, close it all the way down, and set the idle with the screw that limits how far the throttle plate closes.

He says its constantly ever 2 secs, now that isn't normal... It lopes with overlap but it isn't systematic...

I know what loppy idle sounds like, because it is loppy when it is cold idling at 1500 RPM, but steady....the RPMs hold, but it's loppy.

This is like 800-1400-800-1400-800-1400, like I said, it goes up and down at the same speed you would go in and out on your girlfriend at medium pace.

Yeah they will have overlap for sure.... but Ima just saying overlap is not like a systemematic sound in your idle, its goes

bah bah bah blaaah, bah bah blaaah, baah bah bah bah blaaah... its almost random stumbling which that is not what he described... is all I was referring to

Yep.

[240sxxs]

Yeah they will have overlap for sure.... but Ima just saying overlap is not like a systemematic sound in your idle, its goes

bah bah bah blaaah, bah bah blaaah, baah bah bah bah blaaah... its almost random stumbling which that is not what he described... is all I was referring to


due to most part .that is absolutely true.but if is not a cams problem..or overlap issue..then how come the car doesnt have this issues before the OP installed the cams..that is what questioning me

[jspaeth]

due to most part .that is absolutely true.but if is not a cams problem..or overlap issue..then how come the car doesnt have this issues before the OP installed the cams..that is what questioning me


EXACTLY!!!!!!

And I know timing is good....verifired TDC with screwdriver, pulley mark 2nd from left, and aligned mating marks on chains with dots on cam gears.

Rotated pulley by hand to allow the engine to cycle at least 3-4 cycles, then went back to original spot to verify chain is not jumping.etc.

Then, at original setting, put in CAS same way as before, and ligned up line with the correct dot.



Remember....another key thing here is that the idle is FINE while it is cold idling at 1500 RPM.

[240sxxs]

EXACTLY!!!!!!

And I know timing is good....verifired TDC with screwdriver, pulley mark 2nd from left, and aligned mating marks on chains with dots on cam gears.

Rotated pulley by hand to allow the engine to cycle at least 3-4 cycles, then went back to original spot to verify chain is not jumping.etc.

Then, at original setting, put in CAS same way as before, and ligned up line with the correct dot.



Remember....another key thing here is that the idle is FINE while it is cold idling at 1500 RPM.


LoL maybe another phantom mysterious problem on SR20 chart...lol sr20 have so much mysterious problem that unsolve...but hey man ...keep us posted let see what is it...i have a same problem and i end up messing around with the idle screw and it idle SO SO now:ughd: dont know for how long

EDITED : oh one more question...how long did you had the car before installed the cams..and how long did the car act normal with out idle problem until the cams goes in

[slider2828]

yeah maybe IACV.... something fell into it or something... or got stuck... yeah S13SR's are great to work on in general...

Clean the IACV and check it?

[GSXRJJordan]

If the IACV continues to suck and behave UNSTABLE like this, I may just disconnect the harness, close it all the way down, and set the idle with the screw that limits how far the throttle plate closes.

That's what I'd do ~ Stew (Jonny5) runs 264's and removed his IACV entirely, car idles (and comes down to idle) rock solid @ 1100rpm I believe.

[240sxxs]

well zilvian not sure what is it. but it could be anything that make the car idle like that....maybe wrong cams ? lol IDK !! and to the post above ?? so ur friend run with cams and remove completely his iacv and the car idle rock solid at 1100rpm ?? how..idle air CONTROL valve..if the car doesnt have IACV then it wouldnt even turning on without die-ing

[jspaeth]

yeah maybe IACV.... something fell into it or something... or got stuck... yeah S13SR's are great to work on in general...

Clean the IACV and check it?

Thanks for the help everyone.

I will stress again, that prior to the cam install, I drove the car for about 2 weeks, maybe 500 miles total, with no problems, and no idle problems.

Literally the only thing touched was valve cover off, cams on, valve cover back on.

And of course sensors, which are all plugged in.

Verified that TPS sensor reads the same closed and open as before.


I really think it's IACV.....as it cools, down, the oscillations start small and grow....

950-1050-920-1070-900-1100-870-1130....etc. etc. until finally it's bouncing back and forth between 800 and 1400 or so.

ugh



EDIT: Cams are fine....HKS AN-007 and -009 labeled right on the cams themselves when I opened them....and if it was the wrong cams, the car would not run as well as it does when revved to lik 5500 RPM

[240sxxs]

Thanks for the help everyone.

I will stress again, that prior to the cam install, I drove the car for about 2 weeks, maybe 500 miles total, with no problems, and no idle problems.

Literally the only thing touched was valve cover off, cams on, valve cover back on.

And of course sensors, which are all plugged in.

Verified that TPS sensor reads the same closed and open as before.


I really think it's IACV.....as it cools, down, the oscillations start small and grow....

950-1050-920-1070-900-1100-870-1130....etc. etc. until finally it's bouncing back and forth between 800 and 1400 or so.

ugh



EDIT: Cams are fine....HKS AN-007 and -009 labeled right on the cams themselves when I opened them....and if it was the wrong cams, the car would not run as well as it does when revved to lik 5500 RPM



dont stress so much bro. step 3 right ? soon it will solve out or one unexpected days the problem will be fine out....i dont belive that thousand of zilvian cant solve your problem...lol..at least u have a nice car :wiggle:

[jspaeth]

dont stress so much bro. step 3 right ? soon it will solve out or one unexpected days the problem will be fine out....i dont belive that thousand of zilvian cant solve your problem...lol..at least u have a nice car :wiggle:


Thanks man....it USED to look nice...that pic is from like 2 years ago....now there are plenty of chips in the paint, fully cracked front bumper, cracked left sideskirt, cracked left fender etc.

And these are Step 2 cams btw.....I would considering switching over to 264/272 or 272/272 in the future, depending upon what other people with more money to experiment find haha

[240sxxs]

lol..well on frsport they said hsk 272/272 also require hks valve ?

[jspaeth]

lol..well on frsport they said hsk 272/272 also require hks valve ?


I am running BC 0200 retainers and valve springs.

In an independent test, they outperformed many of the other springs, except for Ferrea I think (coil bind onset is much later than others).

Actually, I read that the HKS springs are BARELY an upgrade on stock, in terms of pressure and coil bind.

[johngriff]

almost every hunting idle SR is air in the coolant system. The SR REALLY BADLY wants a pressurized coolant system, when air pockets get into it, it makes the idle hunt. I have fixed NUMEROUS SR's just by jacking the front of the car up, disabling the fans, and getting the engine really hot to bleed the air. Swirl pots work really well for that too. Seems like the air always makes it to the IACV.

I figured that was it b/c you said you removed the head, which would mean your broke pressurization of the coolant system.

Other wise some adjustments with the IACV screw, maybe some more advanced timing at idle (20-22), might fix it. I probably would edit the fuel map as a last resort, and try to play with air fuel through the IACV screw.

[GSXRJJordan]

and to the post above ?? so ur friend run with cams and remove completely his iacv and the car idle rock solid at 1100rpm ?? how..idle air CONTROL valve..if the car doesnt have IACV then it wouldnt even turning on without die-ing

You missed the part about adjusting the throttle body stop ~ there's a mechanical idle adjustment that you can use to keep the throttle body open slightly, even with no throttle applied.

I figured that was it b/c you said you removed the head, which would mean your broke pressurization of the coolant system

That's how I read it too, which is why I thought it was so funny that he's dead set on not bleeding the coolant again.

[Max_PSi]

I would test the coolant temp sensor also. This isn't the first time I've seen an SR hunt for a steady idle and it turned out to be either an air-bound coolant system or a bad sensor not reading the coolant temp properly.

[jspaeth]

almost every hunting idle SR is air in the coolant system. The SR REALLY BADLY wants a pressurized coolant system, when air pockets get into it, it makes the idle hunt. I have fixed NUMEROUS SR's just by jacking the front of the car up, disabling the fans, and getting the engine really hot to bleed the air. Swirl pots work really well for that too. Seems like the air always makes it to the IACV.

I figured that was it b/c you said you removed the head, which would mean your broke pressurization of the coolant system.

Other wise some adjustments with the IACV screw, maybe some more advanced timing at idle (20-22), might fix it. I probably would edit the fuel map as a last resort, and try to play with air fuel through the IACV screw.[/quote]

John, I COMPLETELY see your point about coolant, and it makes sense.

however, it seems like too much of a coincidence that EVERYTHING was fine for 500 miles after i put coolant in, and then RIGHT when I put the cams on, it starts doing this......so that's why I say it's not the coolant.

I have kept adding water to the radiator until it no longer goes down.

Also, the latest time I added the coolant, I literally unbolted the radiator and LIFTED it as high as it could go (mouth of radiator probably 1 foot above valve cover) to aid in the coolant draining down into all cavities, while the car was running......obviously, it will take time to get every last bubble out, but i don't think this is the reason IN THIS CASE for the bad idle.

The stuff I bolded is I think the key.....I have the CAS in the stock position, per the FSM, so the timing and fuel with those cams are almost certainly not optimal.....couple that with the IACV not being set properly, and I think I am seeing some sort of strange underdamped oscillations due to opening/closing of the IACV.

[quote=GSXRJJordan;3095869]You missed the part about adjusting the throttle body stop ~ there's a mechanical idle adjustment that you can use to keep the throttle body open slightly, even with no throttle applied.



That's how I read it too, which is why I thought it was so funny that he's dead set on not bleeding the coolant again.

See above as to why I don't think it's the coolant in my case....would be WAY to coincidental.

I would test the coolant temp sensor also. This isn't the first time I've seen an SR hunt for a steady idle and it turned out to be either an air-bound coolant system or a bad sensor not reading the coolant temp properly.


I know my coolant temp sensor is good.....I can monitor my coolant temps with my PowerFC, and before and after the cam install, they go up while warming up and reach the correct temperature, so that is not it.

[Def]

Flow direction through IACV doesn't matter. It's just flowing through there.

I say open up your IACV screw and see what happens. My MAF voltage went from 0.6 to 0.9% from stock to HKS Step 1 264/264 cams. Took A LOT more air at the same RPM to idle.

[jspaeth]

Okay, so I just went out and spent some time with the car, letting it warm up, etc.

- Car idled smooth again, warmed up, started bouncing.

- Adjusted IACV screw all the way in, and all the way out. In both cases, the idle still bounces, but the center point RPM about which it oscillates either goes up or down.

Then, I accidentally unplugged the CAS while the ignition was ON (not running, but in on position.....I thought I had the keys with me!).

Wasn't sure if this fucked anything up, so I re-cranked the engine to BDC (2nd mark from left), turned car off, plugged CAS back in, and restarted.


- KEY POINT:

I was able to locate a point where I had the pedal down, and the idle was PEFECTLY steady at 1000 RPM and the PFC was reading 15*

- I BARELY had the pedal down. My LOWEST voltage on my TPS is 0.45V when closed all the way, and 4.05V when all the way open.

- The voltage I had it at was literally 0.50V......in other words, I barely had the pedal down at all.

- Had the pedal pushed down so little, that the timing was not being advanced at all, and the revs were steady at 1000.


So, it looks like it's probably an IACV issue. With the car running, I unplugged the IACV, and the car turned right off.

However, even with a SMALL bit of throttle opening, the oscillations go away.

any thoughts?

[johngriff]

hmmm. If you can't get the adjustment you need off the IACV, i would chalk the TB a little. But it always comes back out of place, so tighten it with loctite.

The OTHER, thing I have done is play with the hose length (adding length) to the air feed from the charge pipe to the IACV. Most of the time, I only do this when I am adding an open atmospher BOV to a MAF'd car.

This kind gives more air capacity.

Also, working off your tps idea, try setting base tps voltage up to .5

[jspaeth]

hmmm. If you can't get the adjustment you need off the IACV, i would chalk the TB a little. But it always comes back out of place, so tighten it with loctite.

The OTHER, thing I have done is play with the hose length (adding length) to the air feed from the charge pipe to the IACV. Most of the time, I only do this when I am adding an open atmospher BOV to a MAF'd car.

This kind gives more air capacity.

Also, working off your tps idea, try setting base tps voltage up to .5

Yeah, I mean 0.5V up from a closed throttle of 0.45V is practically almost shut!

How would you reset the base voltage to 0.5 John? Adjust the stud to open the throttle plate a bit, turn car off, unplug sensor, turn car to on position, put plug back in?

I don't want to do anything too drastic, as I need to drive the car 90 miles on Saturday morning to get it tuned.


I am starting to think that maybe with the throttle plate all the way closed, the IACV simply hates the cams, with the timing and fuel the way that it currently is.



Also, did I do a major no-no by unplugging the CAS with the ignition in the on position (but not actually running)?

[johngriff]

Cas is fine, its just 12v, ground, trigger and home. Just an optical sensor, so you probably won't break the cas, maybe send 12v to the ecu, which could be bad. CAS is usually hurt by physical damage before electrical.

[fliprayzin240sx]

Well since were talking about IACV...does anybody know which one of the 2 plugs in an S14 IACV is the Fast Idle Control Valve? I've been having idle bumping issues when the AC is on, thinking of bypassing the ECU and just sending a signal straight into the sensor itself to bump the idle up with the AC on.

Also, happen to know how much signal is needed. I've been hearing different numbers...from 5V, 6V and 12V. Dont wanna send a 12V signal to it and fry it when it only needed a 6V.

http://www.frsport.com/images/detailed_images/Nissan_S14SRIACV_2.jpg

[johngriff]

Well since were talking about IACV...does anybody know which one of the 2 plugs in an S14 IACV is the Fast Idle Control Valve? I've been having idle bumping issues when the AC is on, thinking of bypassing the ECU and just sending a signal straight into the sensor itself to bump the idle up with the AC on.

Also, happen to know how much signal is needed. I've been hearing different numbers...from 5V, 6V and 12V. Dont wanna send a 12V signal to it and fry it when it only needed a 6V.


Do a continuity test between the ecu pin (iirc its 9) and the plug for the IACV.

As far as signal, its a PWM out on the ecu.

Pulse Width Modulation.

So the ecu "cycles" the solenoid to allow the appropriate amount of air through. As long as you keep it wired from the pwm driver its fine, otherwise to "force" the function, switch it to ground.

[jspaeth]

Okay after reading everything, and the fact that everything was FINE before the cams, I am thinking that the IACV, in combination with the timing and fuel, in combination with where my throttle plate stop was set...

all of that + the new cams was just incompatible and leading to a fail idle.

It's strange that just opening the throttle plate every so slightly (0.45V--->0.5V) is enough to make the oscillation go away, but so be it.

If anything else turns up guys, I will let you know.

Thanks for your help.

[2fast4y0u]

i might have to go out and give mine a little adjustment as well.

[Def]

Okay after reading everything, and the fact that everything was FINE before the cams, I am thinking that the IACV, in combination with the timing and fuel, in combination with where my throttle plate stop was set...

all of that + the new cams was just incompatible and leading to a fail idle.

It's strange that just opening the throttle plate every so slightly (0.45V--->0.5V) is enough to make the oscillation go away, but so be it.

If anything else turns up guys, I will let you know.

Thanks for your help.


Like I said, you need to open the set screw on your IACV if just a hair of throttle smooths it out. I'm betting you have such a high duty cycle on your IACV now that by the time it ramps up there it's too high, idle goes up, it cuts the duty cycle by a load, same thing happens all over. It's a controls issue with the stock ECU. Set stuff up so it can get it to all work nice together(i.e. open the screw).

[rc1honda]

I would think you would need to to do the Idle start procedure agian with the Power FC. I have the same cams and a Power FC. My idle was terrible for a awile until i redid the start up procedure and set the idle lower on the Power FC. Now idles steady at 1,000. It's going to idle a little higher becuase of the cams but it should'nt hunt.

I know you probaly have a tune so if you have a dataloggit then save your tune. Intailize the Power FC and do the start procedure again with your injector correction and set the idle to about idle w/ the AC to 1,100 and w/ out the AC to 900. It should settle to around 1,000.

[GSXRJJordan]

Also, did I do a major no-no by unplugging the CAS with the ignition in the on position (but not actually running)?

Not, not an issue.

Do a continuity test between the ecu pin (iirc its 9) and the plug for the IACV.

As far as signal, its a PWM out on the ecu.

Pulse Width Modulation.

So the ecu "cycles" the solenoid to allow the appropriate amount of air through. As long as you keep it wired from the pwm driver its fine, otherwise to "force" the function, switch it to ground.

Exactly ~ it's not like you can just open it up a little bit, you'd have to cycle the solenoid - the voltage you use will simply dictate how fast the solenoid switches. I doubt you could wire it to a switch and get the desired functionality.

[jspaeth]

I could be wrong here, but as far as I know, there is no EXPLICIT control of the IACV in a PFC.

So I'm thinking that someone a few posts up may be on to something.....maybe the way that the PFC learns how to control the IACV is through the initial "Idle learning" when you first plug the PFC in re-initialized.


I may try doing this when I arrive at my tuner's shop tomorrow.

GSXRRJordan.......I have tried adjusting the IACV in both directions....tighter and looser.....it shifts the idle up or down, but it still oscillates rapidly and dramatically......it's like doing that only changes the midpoint about which the oscillations occur.

I think that the IACV-ECU interface is essentially typical closed loop feedback.....so basically, I am thinking that whatever settings are in there for my previous setup....when I put the cams in, the "gain" that the ECU thinks to use is too high when the new cams are in, causing it to always OVERCORRECT from both direction (above or below target idle RPM) leading to the rapid oscillations I am seeing.

[johngriff]

Yeah, I forgot about the PFC relearn.

No, there is no explicit idle control in PFC. There is in Haltech (and its awesome).

Try the relearn, I am still sticking with an air pocket trapped against the thermistor for the IACV.

[jspaeth]

Yeah, I forgot about the PFC relearn.

No, there is no explicit idle control in PFC. There is in Haltech (and its awesome).

Try the relearn, I am still sticking with an air pocket trapped against the thermistor for the IACV.

I hope that that is the case.

I will try pinching and unpinching the hoses going to the IACV, to try to induce flow to it and get any bubble out.

While I think this is a very realistic explanation, it just seems like bad luck on my part then if everything was fine, and then magically a bubble appeared in the IACV RIGHT when I installed the cams, and it has been there ever since.

[jspaeth]

OK this problem was solved today when I got my car tuned.

The cams were causing the vacuum to be a bit different and thus idling on a different part of the map that was too rich, which was causing instability.


After fixing the appropriate cells' fuel and timing, my tuner was able to resolve the issue.

This also involved SLIGHTLY opening the throttle plate a tiny bit more with the stop screw that holds the throttle plate open.



Thank you everyone for your help.


/thread

[2fast4y0u]

well lets not get this one closed just yet.
i didnt get a chance to swap out my iacv but i did get a chance to cold start my car again and let it warm up(open thermostat) before driving
so today i fired it up and let it do its own thing with out touching the throttle. my rpm-s went from 1400 to 650 and basically stalled the car. it was chuggin so bad!
so i gave in and tapped the throttle. once i did that its bounced up and down a few more times then stopped...by stopped i mean the rpm-s didnt bounce. the car idled perfectly and slowly settled down as normal.
my idle sits about 1010 on the high side and 950 on the low side.

so, i need to set motor to TDC, reset the CAS and swap out my iacv. once i have done that maybe i will have some better results.

jspaeth: glad to hear you got the issue resolved. it gives me hope :)

[steve shadows]

Its totally not the cams. Big cams does not make this issue.

More than likely it is air in the coolant system, or an intake leak, or you need to adjust the screw on the iacv, but its not the cams.


Actually Step 2 or larger lift and duration cams will cause idle fluctuation to get a lot worse if the cars previous map was very specifically dialed or is just a general timing setting. Hence you have to add additional advance in the low load cells to bump the cam up. Higher duration means you need to have substantially higher base timing at idle + the power FC idle settings need to be specifically modified for the larger lift cams. Its very simple to do but without the FC logit or the software I dont think you can access all idle functions with the commander.

The cams are causing the idle to be more erratic and what the OP needs to do it increase the pre-load on the IACV screw as well as adjust the idle settings in the PFC and advance the timing cells 1-5 across and 1-5 down in the low corner of the map ( I would suggest 28 degrees).

If the issue still persists than I suggest looking into what your Voltage is and if you alternator is working at full power.

SR20s have a tendency to idle even worse at night when because the Head Lamps and other additional power draw will actually cause the idle to dip lower due to this, you actually need to adjust the battery correction map or make sure your charging system is up to the task 100%

almost every hunting idle SR is air in the coolant system. The SR REALLY BADLY wants a pressurized coolant system, when air pockets get into it, it makes the idle hunt. I have fixed NUMEROUS SR's just by jacking the front of the car up, disabling the fans, and getting the engine really hot to bleed the air. Swirl pots work really well for that too. Seems like the air always makes it to the IACV.

I figured that was it b/c you said you removed the head, which would mean your broke pressurization of the coolant system.

Other wise some adjustments with the IACV screw, maybe some more advanced timing at idle (20-22), might fix it. I probably would edit the fuel map as a last resort, and try to play with air fuel through the IACV screw.

I just saw this post so you did cover some of the similar statements

I would suggest he definitely invests in a swirl pot. Not having a swirl pot on an upgraded SR is totally retarded. Everyone should have one.

Get a radiator pressure tester as well in addition to your compression test you need to be doing (to the OP)

[Def]

Seriously, how are you guys having such a hard time bleeding the cooling system on these motors? It's not rocket science. Follow the FSM - use the bleeder screw. Jacking the front up helps a little but usually isn't necessary.

[steve shadows]

Seriously, how are you guys having such a hard time bleeding the cooling system on these motors? It's not rocket science. Follow the FSM - use the bleeder screw. Jacking the front up helps a little but usually isn't necessary.

If you're going to beat the shit out of your car at a road track or drifting you MUST get a swirl pot, then you will never have to bleed again.

Bleeding is a pain in the ass if you as me. You have unscrew the screw on the water jacket them let all the air get out then as the car is running you start to get a gyser of burning hot water and then you have to effectively screw the bolt back in there. And you will have to do this after every track day, sometimes after every set of laps on the course. Totally annoying. Just get a swirl pot, then you have no worries and never have to bleed the stupid water jacket every again.

[2fast4y0u]

what in Sam Hail is a swirl pot? im going to google this :)

[jspaeth]

Seriously, how are you guys having such a hard time bleeding the cooling system on these motors? It's not rocket science. Follow the FSM - use the bleeder screw. Jacking the front up helps a little but usually isn't necessary.


What the hell are you talking about. I already had the problem fixed by the tuner. It had nothing to do with coolant bleeding.

The cams were causing the car to idle in portions of the map (like Steve said) that were previously not being accessed during idle......the car was running way too rich, plus the whole timing thing.

We got the problem fixed. The car now idles high (like 1200-1300), but very steady.....with a minor adjustment to the throttle body stop screw to let a little bit more air in.

[P-Funk alot]

ok i have been through this plenty of times with my customers. since im not there i cant pin point it but you may wanna check your cams again i have seen it many times where the exhaust side is off one tooth the car will be a rocket when your on it but will idle very rough and i would also look into your tune your previous tune was set for stock cams to a t and now that you have your cams in it will change alot and when you do your timing on your gun go plus 15 degrees which should show top dead but i wouldt worrie if you say your sure your timing is right its gonna be in your tune good luck with it hope i helped

[Def]

If you're going to beat the shit out of your car at a road track or drifting you MUST get a swirl pot, then you will never have to bleed again.

Bleeding is a pain in the ass if you as me. You have unscrew the screw on the water jacket them let all the air get out then as the car is running you start to get a gyser of burning hot water and then you have to effectively screw the bolt back in there. And you will have to do this after every track day, sometimes after every set of laps on the course. Totally annoying. Just get a swirl pot, then you have no worries and never have to bleed the stupid water jacket every again.

Not if you properly bleed your cooling system and don't havea headgasket leak that's letting combustion gasses into the water jacket.

I never have to touch mine except when I drain it, then it takes about 5 mins to completely bleed it.

Seriously, it's not that hard.

[Def]

What the hell are you talking about. I already had the problem fixed by the tuner. It had nothing to do with coolant bleeding.



I'm talking about everybody saying you magically get air introduced into an SR's cooling system and how hard they are to bleed - what the hell do you think I'm talking about?

Idiots... :smash:

[jspaeth]

I'm talking about everybody saying you magically get air introduced into an SR's cooling system and how hard they are to bleed - what the hell do you think I'm talking about?

Idiots... :smash:


Oh I guess I misread what you wrote. I think we were actually in agreement hahah.

[2fast4y0u]

i adjusted my stop screw yesterday to have it read .5v
im gonna try the cold start on it today and see what happends

[2fast4y0u]

i adjusted my throttle body stop screw today.
on my afc, i went from throttle voltage of .45 to .5v

on a cold start, my idle goes from 1200 to 1000. thats the only drop it makes. it does it like 2 or 3 times and thats it. then everything is normal and great.
car runs amazing and doesnt stall when i press the clutch to brake/come to a stop.
FINALLY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!