SR20DET Stalling in neutral/decel - IACV?

[lagvoid21]

I've been researching for over a week now, trying to avoid posting YET ANOTHER THREAD on this subject, but have given up.

When I first start the car (cold), the idle is steady and does not stall. Once the engine is warm, the idle drops to ~800 rpm. If I blip the throttle, the rpm's drop down real low ~500 and sometimes stalls. If I rev up 3k+ and let off the gas, it will definitely stall coming down. The engine appears to be running REALLY rich when it stalls. I can't start the engine back up unless I give it gas...


I am running a TD-06 turbo and it does not make any boost revving in neutral.

Here is what I have tried up til today:

-new plugs
-TPS voltage is right (.43 closed and 4+ open)
-dumped a lot of intake cleaner down tube to IACV
-dumped a lot of carb cleaner
-dumped a lot of seafoam
-tried decel-air setting on afc-2
-removed iacv to clean with degreaser (brake cleaner and oil eater)
-removed iacv again to clean with superclean
-disconnected battery to reset ecu in hopes of having ecu relearn
-sprayed starter fluid on couplers/vac lines
-checked for vacuum leaks
-adjusted idle (using tb set screw and iacv adjustment knob while tps and iacv disconnected)
-pulled vacuum off bov and plugged
-filled coolant

The IACV is adjusting when I turn the screw, however the idle drops too low and often stalls. Even with a blip it will seek around for idle and stall unless I very lightly hold the rpms and slowly let off.

740cc injectors
hks ssqv (open atmosphere)
td06 turbo
z32 maf
greddy intake manifold
nismo fpr
hks step 2 cams
enthalpy rom
safc-2 (no longer installed)

I never had this problem with a smaller turbo running the same BOV open atmosphere. Is my IACV dead? I was unable to find how I could test if the spring was working or if it was sealing properly when the unit was removed.

I really appreciate anyone taking the time to read this. Please help me!

[Homer_Simpson]

Even you've set the decel, have you tried recirculating your BOV to see if it makes any difference?

[lagvoid21]

Even you've set the decel, have you tried recirculating your BOV to see if it makes any difference?

I have not, since I do not have the kit to do so. I did remove the vacuum to the BOV and plugged the line, which should be the same thing as running no BOV right?

[OBEEWON]

How long have you been running on that enthalpy tune?

I trouble shot for weeks before I found out one of my chips was blank, and the other had a honda tune on it.

[OBEEWON]

I have not, since I do not have the kit to do so. I did remove the vacuum to the BOV and plugged the line, which should be the same thing as running no BOV right?

Unless your BOV is leaking.

Do you have a wideband?

[lagvoid21]

I've had this tune for awhile now, but the stalling only seemed to get worse until it's current state of stalling even in neutral.

I don't have a wideband. I did spray starter fluid all around the BOV and did not notice any difference. I did a leak test and eliminated them but they were minor and had no effect on my stalling issue.

[0wn3r]

you can try cleaning your MAF, it may help slightly, though I still ran into an issue the other day where it was dropping and stalling out when warm...usually it's clutch in and braking it will stall

i'm recirc

[landins13]

this happends to a lot of large turbo sr20's you can fix it if your car has a legit tune, not just a rom flash, ie, apexi, nistune, aem, hks fcon, those sort of programs are fine tunable enough to stop the problem, honestly your going to have to catch the throttle when your driving the car. down shift as far as you can so 5-4-3-2-1 and when the car almost stalls out push in the clutch and rev the throttle a little,
the car should balance out, it just cant handle the drop from 4-5k to 1k in rpm

[slider2828]

Yeah, I would also check for more small leaks as well. You can try closing your IACV and the screw for the throttle plate where the throttle wheel rests on, turn it in so when the plate is fully closed there is still a sliver of air going into your intake for idle.....

Check and redo your grounds too! This is going to be a biggy, if you step on the break and notice some fluctuations like light flickering and stuff... redo grounds with 2 gauge monster cables.... Those will definitely help.

[singlecamslam]

i have a similar problem. when i put it in neutral after a drive the car will die. I know its my IACV, the way i checked it was i took the hose that goes to the IACV from the cold pipe and twisted it closed, and my idle got much better. I dont know if that will help.

[lagvoid21]

you can try cleaning your MAF, it may help slightly, though I still ran into an issue the other day where it was dropping and stalling out when warm...usually it's clutch in and braking it will stall

i'm recirc

I will definitely try this. I don't think I've ever cleaned my maf. Thanks

this happends to a lot of large turbo sr20's you can fix it if your car has a legit tune, not just a rom flash, ie, apexi, nistune, aem, hks fcon, those sort of programs are fine tunable enough to stop the problem, honestly your going to have to catch the throttle when your driving the car. down shift as far as you can so 5-4-3-2-1 and when the car almost stalls out push in the clutch and rev the throttle a little,
the car should balance out, it just cant handle the drop from 4-5k to 1k in rpm

I agree with you, but I have a couple friends running very similar setups with no issues at all. I think enthalpy's tune is off on the low end. I need to get a wideband when $ comes around. Today I reconnected the safc2 and reset the decel and it helped out a lot. I think the combination of cleaning the iacv multiple times, retightening couplings, and resetting the decel air function has my car in better shape than its been in awhile. I will take it out for a more thorough test this weekend to see.

Yeah, I would also check for more small leaks as well. You can try closing your IACV and the screw for the throttle plate where the throttle wheel rests on, turn it in so when the plate is fully closed there is still a sliver of air going into your intake for idle.....

Check and redo your grounds too! This is going to be a biggy, if you step on the break and notice some fluctuations like light flickering and stuff... redo grounds with 2 gauge monster cables.... Those will definitely help.

I messed around with the throttle set screw and iacv screw a lot but it didnt help with the stalling. I will double check the grounds though, thanks for the suggestion!

i have a similar problem. when i put it in neutral after a drive the car will die. I know its my IACV, the way i checked it was i took the hose that goes to the IACV from the cold pipe and twisted it closed, and my idle got much better. I dont know if that will help.

Hmmm I've been reading and reading about the IACV and understand some of how it works (ie. cold start pulling air until coolant opens the next valve) but I don't understand what effect closing off that hose you mentioned has. I will add it to my check list though, thanks.

[240sx blue pearl]

Did you ever get anywhere with this? I'm in the same boat right now and it drives me crazy.. Like you said only from a more agressive decel to neutral, it falls on its face. IACV clean as a whistle too.

As far as this being normal I don't think so.

How is your IGN timing?
Do you have any missfires or a rough idle?

I'm gonna chase down the BOV issue a little more. Like posted above if it leaks that could be a problem.. plus a buddy of mine had the same issue with the greddy RS (wich is what I have now).. Fixed with a diff BOV

[lagvoid21]

I replaced the iacv and the situation improved but has not been completely eliminated. I have not had time to drive or trouble shoot the past months. When I do get back to it, I plan to clean the iacv again and increase idle. My ign timing was accurate the last time it was checked. Idle is slightly rough but could be due to step 2 cams. I chased down many leaks before but it did not have much effect on the situation. good luck!

[slidewaysmn]

Had the same problem with my sr...cleaned the tb a few times, but ended up having to adjust the set screw on it, so the butterfly would still stay open. Idles up, but doesn't die.

[Csomme]

Had the same problem with the same BOV. BOV was complete shit.

Got a new one that isn't broken/ doesn't leak. fixed the problem.

Try this to see if it works:

unplug the BOV, plug the line, have someone start the car, and with your hand, cup your palm over the opening on the BOV, and use your finger to cover the small vacuum nipple.

if that makes it idle, get a new BOV and go blow thru.


DO this regardless of the BOV you have.

[240sx blue pearl]

Had the same problem with the same BOV. BOV was complete shit.

Got a new one that isn't broken/ doesn't leak. fixed the problem.

Try this to see if it works:

unplug the BOV, plug the line, have someone start the car, and with your hand, cup your palm over the opening on the BOV, and use your finger to cover the small vacuum nipple.

if that makes it idle, get a new BOV and go blow thru.


DO this regardless of the BOV you have.

What BOV are you referring to that you had?
I'm having the same problem still tps good iac clean as a whistle timing set. there has got to be a way to fix this

P.S. How do you go about cleaning your MAF? I've seen brake cleaner and steel wool suggested, but does that hurt it? carb cleaner???

[lagvoid21]

stores sell MAF cleaner that u spray directly on the sensor.

[nothix]

stores sell MAF cleaner that u spray directly on the sensor.
+1 use the purpose made cleaner.

[2fast4y0u]

WOW! seems like this is a large issue because i to have very similar issues.
2871rs
step 2 cams
z32 maf
850cc injectors
recirc BOV
greddy intake
Enthalpy rom tune
yadda yadda yadda

i just bought another iacv to test mine to it. i tried adjusting the screw in it and nothing. i havent really messed with the Throttle body set screw though.

i was told as well, and this couldnt be complete BS but if you are running a slim battery such as me, the slim batteries dont have enough reserve power to compensate the voltage draw when your idle is lower. My alternator doesnt charge the battery at startup unless i rev the car to about 3k rpm's then it will start the charging. i have taken it to auto zone, napa, car quest and they all say its good. BUT ITS NOT!!!

so point of my ranting here is check your voltage as well, especially on your decel. mine drops off like crazy...something like into the 11v area

oh, how are you setting your AFC on the decel? i guess i have missed that feature

[240sx blue pearl]

WOW! seems like this is a large issue because i to have very similar issues.
2871rs
step 2 cams
z32 maf
850cc injectors
recirc BOV
greddy intake
Enthalpy rom tune
yadda yadda yadda

i just bought another iacv to test mine to it. i tried adjusting the screw in it and nothing. i havent really messed with the Throttle body set screw though.

i was told as well, and this couldnt be complete BS but if you are running a slim battery such as me, the slim batteries dont have enough reserve power to compensate the voltage draw when your idle is lower. My alternator doesnt charge the battery at startup unless i rev the car to about 3k rpm's then it will start the charging. i have taken it to auto zone, napa, car quest and they all say its good. BUT ITS NOT!!!

so point of my ranting here is check your voltage as well, especially on your decel. mine drops off like crazy...something like into the 11v area

oh, how are you setting your AFC on the decel? i guess i have missed that feature


ive heard of this being a problem before too.. but according to my little radar detector, its a constant 14.0v-14.4v. going to see if i can pick up some of that MAF cleaner tonite. and as far as opening up the throttle plate to compensate, that is a last resort for me. I think there has got to be somthing up with this.

[2fast4y0u]

yeah i dont want to be messing with the set screw. that cant really be the fix for this.

[nothix]

WOW! seems like this is a large issue because i to have very similar issues.
2871rs
step 2 cams
z32 maf
850cc injectors
recirc BOV
greddy intake
Enthalpy rom tune
yadda yadda yadda

i just bought another iacv to test mine to it. i tried adjusting the screw in it and nothing. i havent really messed with the Throttle body set screw though.

i was told as well, and this couldnt be complete BS but if you are running a slim battery such as me, the slim batteries dont have enough reserve power to compensate the voltage draw when your idle is lower. My alternator doesnt charge the battery at startup unless i rev the car to about 3k rpm's then it will start the charging. i have taken it to auto zone, napa, car quest and they all say its good. BUT ITS NOT!!!

so point of my ranting here is check your voltage as well, especially on your decel. mine drops off like crazy...something like into the 11v area

oh, how are you setting your AFC on the decel? i guess i have missed that feature
so are you saying that all you need to fix your problem is a new alternator or a new battery?

[clark]

so are you saying that all you need to fix your problem is a new alternator or a new battery?

ummmm did he yadda yadda his engine modifications?

[240sx blue pearl]

Ok, I've gotten somewhere with this.
So far I have checked timing, repositioned tps according to spec, cleaned MAF, removed\ cleaned IACV, and the problem has basicly gone away. I drove a decent ammount today trying to get it to stall everywhere I went, but it only falls to about 650ish. Only once did it fall below that but it did not stall. I think the MAF cleaner is what did the trick.

[2fast4y0u]

so are you saying that all you need to fix your problem is a new alternator or a new battery?

im not saying that is all i need to do.

ummmm did he yadda yadda his engine modifications?

i have posted my build list somewhere on here, i just dont feel like typing it all the time


I got my tuned ecu back from RS Enthalpy yesterday. plugged it in and fire up the car. To my suprise the car GREAT! No misfire issues and it idles at like 950(which is what i wanted), i revved it up and it almost stalled but it caught itself and kept running. I know its not the same as when its under a load in driving conditions but its a start.:coold:

[zylvia213]

Dam i have the same exact problem.... just that my car is pretty much stock. Only thing is blitz BOV, FMIC, nismo FPR, and i think that pretty much it. I've had this problem for a while now and it is anoying. I will try some of these suggestions on this thread and see how it goes.

[Def]

Open up your IACV set screw. Your engine will take about 30-40% more air at idle with those cams due to the overlap. With the set screw set for stock cams your IACV duty cycle is way higher, which is fine on a steady state idle. When it needs to let in a lot of air quickly like clutching in and catching the idle it will not ramp up the duty cycle of the IACV fast enough and you'll get some sputtering and stalling.

Trust me, it takes only a few seconds to give the IACV a few extra turns open. Remember, it's counter clockwise as you're looking at the IACV, so the bottom mounted IACV on a GReddy/FReddy intake mani needs to be turned so the screw is going CCW.

Don't turn it so much you raise the idle, but I think you'll find you can easily give it a turn or two and not affect your idle at all, and then you'll enjoy no stalling.

[2fast4y0u]

/\
i turned mine the other day 1 full turn counter clock wise, idle didnt change but it does seem to catch it self a little better. sounds like 1 more turn may do the trick

[nothix]

I'll try messing with mine tonight

[clark]

hey Def, good post. i don't have the stalling issue, but when i clutch in my idle does dip too, and i've always been unrested about it,b ut i've NEVER stalled.

i never wanted to screw with the iacv screw because i thought even a small turn would change my idle. i too am going to try this in hopes that when i clutch in and come to a stop, my idle will "catch itself" a little better.

+1 fake rep.

[s15specR]

Ok, I've gotten somewhere with this.
So far I have checked timing, repositioned tps according to spec, cleaned MAF, removed\ cleaned IACV, and the problem has basicly gone away. I drove a decent ammount today trying to get it to stall everywhere I went, but it only falls to about 650ish. Only once did it fall below that but it did not stall. I think the MAF cleaner is what did the trick.


How exactly are you repositioning the TPS, that's the only thing I changed, and I'm having this problem.

[ross.cottrill]

How exactly are you repositioning the TPS, that's the only thing I changed, and I'm having this problem.

you have to set it with a voltmeter.i set mine to 4.5v.

[240sx blue pearl]

you have to set it with a voltmeter.i set mine to 4.5v.

exactly.

For an S14 SR the resistance across the TPS should be .7k ohms closed to 5k ohms open. ..when it is unplugged and key is off

To adjust it, you have to loosen the 2 screws then turn it with your hand

[s15specR]

Gonna try this right now, thanks.

[supradealz]

usually iacv problems tend to have cold start issues when the temperature is cold.
my car ran fine all summer cold starts, i started it up when it was 65 degrees out and its running so lumpy with my step 2 264 cams i thought i was on 3 cylinders. soon as it warmed up it was fine. my iacv needs replacement soon anyways.
it used to be so bad when i started it up when it was cold i had to keep the TB open manually else it would stall until it warmed up...then it purred perfectly.

[lazysk8er2]

same problem here too just put the enthalpy ecu in...gona check for vacuum leaks.

[2fast4y0u]

same problem here too just put the enthalpy ecu in...gona check for vacuum leaks.

if u still have issues, just email/call enthalpy...they will get you all fixed up