SR Idle Woes (Again)

[pacotaco345]

So I sorted out the prior idle issues (swapped IACVs and re-did my maf wiring) and now I have a new issue. When the alternator is under any kind of load the idle jumps up about 500 rpm, give or take a couple hundred depending on how great the load is. Examples: (I have electric fans wired to ignition that I can unplug)

- Car on, all electronics turned off fans unplugged. Car wont idle at all (~450 ish rpm)
- Car on, fan on low, everything else off ~850 rpm
- Car on, fan on low, brakes (brakelights) on ~1k rpm
- Car on, fan on low, lights on ~1400 rpm

It seems to level off around 1500 rpm if I literally have every electronic in the car on. If anyone has any ideas of what it could be let me know. I've asked/searched everywhere for answers.

[pacotaco345]

bump, anyone?

[djras1]

Unplug your tps there is a idle screw on the throttle body adjust till you are able to consistently get 850 rpm takes a lil while to get it into timing mode
good luck

[dorkidori_s13]

Unplug your tps there is a idle screw on the throttle body adjust till you are able to consistently get 850 rpm takes a lil while to get it into timing mode
good luck

uh, DONT do this... your throttle body screw is specifically for setting TPS voltage and unless you have a multimeter handy or are using NISTune/ECUTalk with a consult cable. normal range for your TPS/Throttle body needs to be set at .38 to .4 volts. if you start messing with the screw and drop it above or below the normal range voltage, your ECU will freak out and start causing either heavy rich or heavy lean states depending on idle and throttle position. Also, if the TPS is outside of its normal range, the car will not enter into proper idle mode (its a lean loop the ECU drops into when youre sitting at idle to help with gas consumption... the motor will drop from 1000rpms to a steady 750rpm).

regarding the OPs question, rather concerns, how far open do you have your IACV? if youre not averaging an idle of 1000-1200 (then dropping into idle loop), your IACV is not set properly. also do you have an adjustable fuel pressure regulator? when was the last time you actually CLEANED the MAF (remove it from house, clean with B12 carb cleaner and a Q-Tip)? have you boost leak tested the car? is your air filter clean? are you using a GOOD air filter? (not some cheap autozone Spectre joint)

[djras1]

worked for me but ill take your word for it had a similar problem and i had nistune.

[dorkidori_s13]

worked for me but ill take your word for it had a similar problem and i had nistune.

your solution wasnt the proper one then... that screw is meant to sit at .4 volts and thats it. anything higher or lower and your tune was wrong. idle is only meant to be adjusted via the IACV. throttle set screw is only for the TPS voltage.

[pacotaco345]

Unplug your tps there is a idle screw on the throttle body adjust till you are able to consistently get 850 rpm takes a lil while to get it into timing mode
good luck

Are you talking about the little set screw with the jam nut on the throttle body? or the two screws you use to adjust the TPS... Either way my little set screw just holds the throttle open enough to keep it from sticking shut (which is 99.99999% closed) and my tps reads around .38v at idle.

uh, DONT do this... your throttle body screw is specifically for setting TPS voltage and unless you have a multimeter handy or are using NISTune/ECUTalk with a consult cable. normal range for your TPS/Throttle body needs to be set at .38 to .4 volts. if you start messing with the screw and drop it above or below the normal range voltage, your ECU will freak out and start causing either heavy rich or heavy lean states depending on idle and throttle position. Also, if the TPS is outside of its normal range, the car will not enter into proper idle mode (its a lean loop the ECU drops into when youre sitting at idle to help with gas consumption... the motor will drop from 1000rpms to a steady 750rpm).

regarding the OPs question, rather concerns, how far open do you have your IACV? if youre not averaging an idle of 1000-1200 (then dropping into idle loop), your IACV is not set properly. also do you have an adjustable fuel pressure regulator? when was the last time you actually CLEANED the MAF (remove it from house, clean with B12 carb cleaner and a Q-Tip)? have you boost leak tested the car? is your air filter clean? are you using a GOOD air filter? (not some cheap autozone Spectre joint)

The IACV is currently screwed all the way in. If my fans are completely off (which they never are unless I unplug them), it tries to idle around 500 rpm and just dies. With the fans on low (all the time) it idles at about 850. Any time other electronics (with the exception of the radio) are on it bumps to over 1k. I cleaned my maf with maf cleaner, it doesn't have any boost leaks, i have an oem fpr, and i'm using a cheapo spectre air filter... The thing is, this issue seems to be related to alternator load and not any real input that the ecu is getting...

**the best way I can describe whats happening is any time something gets turned on, the car is assuming I turned the air conditioning on and bumps the idle up, except it keeps rising with each thing I turn on.

[pacotaco345]

If I unplug the fans, I can adjust the IACV to some normal range and it'll happily brap along at 800-850 rpm with the cams as long as everything is turned off. (I really just want it to idle low so I can hear my cool cams lol)

[dorkidori_s13]

Are you talking about the little set screw with the jam nut on the throttle body? or the two screws you use to adjust the TPS... Either way my little set screw just holds the throttle open enough to keep it from sticking shut (which is 99.99999% closed) and my tps reads around .38v at idle.

if your TPS is at .38v youre fine. i meant to type .35 to .42 volts earlier (was in a hurry)


The IACV is currently screwed all the way in. If my fans are completely off (which they never are unless I unplug them), it tries to idle around 500 rpm and just dies. With the fans on low (all the time) it idles at about 850. Any time other electronics (with the exception of the radio) are on it bumps to over 1k. I cleaned my maf with maf cleaner, it doesn't have any boost leaks, i have an oem fpr, and i'm using a cheapo spectre air filter... The thing is, this issue seems to be related to alternator load and not any real input that the ecu is getting..

your IACV screw SHOULD NOT be tightened all the way down, thats more than likely whats causing all of your issues. on my blacktop (s13), im about 6-7 turns out i believe, and im pretty sure the s14/s15 notchtops are the same way. having the IACV screwed all the way in, youre not allowing air into the chamber to allow the piston to actuate idle properly. im not 100% certain on the names for the internals on an IACV but there is a small piston that opens and closes to allow are in and out of the IACV sensor and having the screw fully tightened down will not allow the IACV to function properly. back it out 4-5 turns and see what happens with your idle. in normal mode (before idle mode kicks in) the car should drop to 1000-1200 rpms (depending on temperatures outside), then drop to 700-800 rpms after about 5-10 seconds and kick itself into idle loop (which is normal). having your accessories turned on in the car (lights, blower motor, radio etc) will cause the idle to drop just slightly in idle loop, but this is normal. fuel pressure will also affect your idle. if youre running an OEM FPR, then youre sitting around 58-65psi if youre running a walbro fuel pump. get yourself an adjustable FPR WITH A GAUGE and set your fuel pressure down to 40psi (45-50 if youre over 12psi on a S14 or S15 T28). you will need to re-adjust your IACV screw once you bring your fuel pressure down as it will idle in higher RPMs with higher amounts of fuel pressure on stock injectors. also, replacing your FPR with an adjustable unit will net you back 2-3 miles per gallon.

do yourself a favor and invest in a K&N air filter as well, makes a rather large difference! its cleanable and flows much better than those stupid spectre filters (those things arent worth the $20 theyre priced at).

[pacotaco345]

if your TPS is at .38v youre fine. i meant to type .35 to .42 volts earlier (was in a hurry)




your IACV screw SHOULD NOT be tightened all the way down, thats more than likely whats causing all of your issues. on my blacktop (s13), im about 6-7 turns out i believe, and im pretty sure the s14/s15 notchtops are the same way. having the IACV screwed all the way in, youre not allowing air into the chamber to allow the piston to actuate idle properly. im not 100% certain on the names for the internals on an IACV but there is a small piston that opens and closes to allow are in and out of the IACV sensor and having the screw fully tightened down will not allow the IACV to function properly. back it out 4-5 turns and see what happens with your idle. in normal mode (before idle mode kicks in) the car should drop to 1000-1200 rpms (depending on temperatures outside), then drop to 700-800 rpms after about 5-10 seconds and kick itself into idle loop (which is normal). having your accessories turned on in the car (lights, blower motor, radio etc) will cause the idle to drop just slightly in idle loop, but this is normal. fuel pressure will also affect your idle. if youre running an OEM FPR, then youre sitting around 58-65psi if youre running a walbro fuel pump. get yourself an adjustable FPR WITH A GAUGE and set your fuel pressure down to 40psi (45-50 if youre over 12psi on a S14 or S15 T28). you will need to re-adjust your IACV screw once you bring your fuel pressure down as it will idle in higher RPMs with higher amounts of fuel pressure on stock injectors. also, replacing your FPR with an adjustable unit will net you back 2-3 miles per gallon.

do yourself a favor and invest in a K&N air filter as well, makes a rather large difference! its cleanable and flows much better than those stupid spectre filters (those things arent worth the $20 theyre priced at).

Sounds good, I'll start with backing the IACV out tomorrow and see what happens. The rest will have to wait til my next paycheck lol. When I had the IACV backed out about 2 turns before though it just seemed to idle even higher than it was now so idk.

[dorkidori_s13]

with the IACV backed out, it will idle higher... BUT, when its properly adjusted, like i said, the car will idle at 1000-1200 rpms momentarily (especially during out of gear slow downs) but its supposed to drop down to 750-800rpms after a few seconds to go into idle loop. you need to adjust the IACV after the car is warmed up as cold loop is a totally different map in the ECU ROM and will cause the car to usually idle around 1500-2000 rpms when its cold. the car will open its thermostat after about 3-5 min of warming up (initial warm up opens the thermostat at 170deg). once the thermostat opens, the car drops out of cold loop to normal operating mode.

[pacotaco345]

with the IACV backed out, it will idle higher... BUT, when its properly adjusted, like i said, the car will idle at 1000-1200 rpms momentarily (especially during out of gear slow downs) but its supposed to drop down to 750-800rpms after a few seconds to go into idle loop. you need to adjust the IACV after the car is warmed up as cold loop is a totally different map in the ECU ROM and will cause the car to usually idle around 1500-2000 rpms when its cold. the car will open its thermostat after about 3-5 min of warming up (initial warm up opens the thermostat at 170deg). once the thermostat opens, the car drops out of cold loop to normal operating mode.

I understand cold start vs operating temp running conditions, right now, assuming the fans and nothing else are on, it will do as you say. Drop to about 1000-1200 then the rest of the way to 850, this is with the IACV screwed all the way in.

When you go about adjusting idle do you bother to do the whole rev to 2k thing, shut car off, unplug tps, bla bla bla.. Or do you just warm the car up and adjust the screw.. I've heard different opinions.

Also, I guess I assumed everyone had read my previous idle thread stating the cars setup. It has:
s14 bb t28
walbro
stock fpr
poncams
greddy intake
lightweight flywheel
forged internals
550cc injectors
z maf
enthalpy tune

[dorkidori_s13]

ooooooooooo, didnt realize you had a custom tune on your car. everything im telling you is based on a stock ECU. it may have to do with your enthalpy tune being too rich or too lean at start up. custom tuning takes a bit of work to get the car to run well with both cold and warm starts.

as far as adjusting your IACV, ive never unplugged the TPS or any of that bullshit. just got the car warm, drove it around a bit and messed with the IACV. that was after i properly set the TPS set screw though (which i did by the FSM instructions which i believe is unplug it, set voltage, shut car off, plug back in then double check voltage). the IACV really isnt that bitchy of a sensor. once you get it set right, you rarely need to screw with it.

i would HIGHLY recommend you get rid of that enthalpy tune and go with a full stand alone. ROM tunes were great in the late 90s/early 2000s, but honestly with the advent of the AEM standalone and the PowerFC DJetro, theres no reason to waste money on a ROM. too many variables can go haywire and cause problems with a ROM tune. with a stand alone, you have the ability to adjust everything ECU wise to accommodate any changes or problems with the motor.

[dorkidori_s13]

since you are messing with a custom tuned ROM in your ECU and trying to trace electrical issues, i would HIGHLY suggest you buy a consult plug and download ECU talk for windows (the consult plug is USB based). this will allow you to monitor all of your sensors and voltages to properly adjust everything. its a great and very cheap set of tools that have helped me diagnose a TON of shit that was wrong with my motor.

and just to make sure, youre running an S13 redtop/blacktop correct?

[pacotaco345]

Yes its an s13 blacktop. As far as the tune, it ran okay before I blew up the previous motor (idle and everything). With the new motor nothing has really changed besides the greddy manifold and the bottom end (which retained the same CR) so I don't see why that should cause any issues. The *only* thing I haven't really had a chance to screw with is the routing of my fuel return line. With the new position of the manifold it bends the return line a bit more than I'm comfortable with so I think I may be pretty rich atm. That said, I just ordered a tomei fpr and all the stuff that goes with it so it should be taken care of pretty soon.

I'll take a look at ECU talk also, I have friends in socal with that kind of software that I used to borrow but none out here in texas so I'm kinda hung out to dry when it comes to that.

[dorkidori_s13]

ECUTalk is freeware (the full version allows data logging and what not) and all of the gauges/sensors/readouts work. Its a neat piece of software and works on any windows based machine (i run mine on a netbook i bought back in 2009). I think you can pick up a Nissan Consult Cable off ebay for like $80. I know for a fact it works with S13 blacktops just fine as I use one with my quite often. In the link below you can see the ECUTalk software (first pic with all the simple looking gauges).

http://www.ebay.com/itm/ECUTalk-USB-Nissan-Consult-Cable-Skyline-Silvia-300ZX-/321572730403?pt=AU_Car_Parts_Accessories&hash=item4adf3a7623

man im halfway tempted to buy one now hahahahah. i always just bum one off my friend who owns a shop out here lol

[Def]

You sure you don't have a vacuum leak? Not sure why it'd be worse with a higher idle, but the IACV by itself can't get the idle that high even wide open if you have the bypass screwed down.

[pacotaco345]

No vacuum/boost leaks or anything like that. Also, like I said its dependent on alternator load. If everything is shut off it idles right along at 850

[dorkidori_s13]

hey man, any luck with adjusting your IACV?

[pacotaco345]

No luck yet, I think it's crazy rich because it'll break up under full boost then wont rev clean for a while after.. I'm throwing an FPR and new plugs on it today and I'll see where I'm at after all that

[dorkidori_s13]

have you tried boost leak testing the car by actually pressurizing the system while the car is off? if youre going crazy rich and breaking up under load, you more than likely have a boost leak AFTER the turbo (before the turbo causes lean situations)

[pacotaco345]

I haven't boost leak tested it because I don't have access to everything needed to do so. I did however put the fpr and plugs on it and it got a little better mileage and revs much cleaner (the whole rev like shit after boosting issue is gone) and the idle cleaned up a bit. So now I have 99% of the problems solved it just breaks up at high rpm in boost under decent load. It doesn't fall on its face but it almost sounds like a hard rev cut.. Here's a video link to my tumblr, sorry about the whole street drifting thing zilvia. You kinda have to listen for it but you'll definitely be able to hear it after corner exit.

http://sidewaysfordays.tumblr.com/post/101829293752/smooth-like-keith-stone

[dorkidori_s13]

break up at higher RPMs is usually MAF related, not enough fuel or a boost leak...

[silverarrow27]

One of your earlier posts you said one of your fuel line is bent more than you'd like. That might be your issue, kinked fuel lines mean you're running too lean. Not too rich. Then again is it your feed or return line?

[pacotaco345]

One of your earlier posts you said one of your fuel line is bent more than you'd like. That might be your issue, kinked fuel lines mean you're running too lean. Not too rich. Then again is it your feed or return line?

Fixed that when I put the new fpr on. It was the return line. That sorted some of the issues but the breaking up under boost thing is still there. I'm gonna gap the plugs down to .025 from .030 sometime here and see what that does.

[ultimateirving]

Fixed that when I put the new fpr on. It was the return line. That sorted some of the issues but the breaking up under boost thing is still there. I'm gonna gap the plugs down to .025 from .030 sometime here and see what that does.

The plug gap at .030 should be ok for stock boost levels. If your getting blowout it could be a faulty coil pack, I had a coilpack that would fire/function under normal load. But would break up really bad under boost/heavy throttle.

[pacotaco345]

The plug gap at .030 should be ok for stock boost levels. If your getting blowout it could be a faulty coil pack, I had a coilpack that would fire/function under normal load. But would break up really bad under boost/heavy throttle.

Wellllll I'm running 17 psi on an s14bb t28 with poncams. So its safe to say the motor is getting a decent amount of air lol.