Chevelle505

Hey all...need a little help here..87 Iroc 305TPI/auto G92...got an issue that i cant seem to track down and have checked all that i can think of. Only when wamed up at temp she occasionally wants to die at idle in gear only..if i ever so slightly crack the throttle shes fine...in neutral shes fine..when cold shes fine. It sounds like its almost wanting to idle to low..if i crack the throttle a tad she wont die. Car runs and drives fine..no misses and blows the tires off..its just this idle issue with no other symptoms.
it doesn just cut off like a bad connection either..she kinda stumbles for a second or two..enough warning to crack the throttle. Sometimes after i crack the throttle she wont do it..it will maintain idle. And like i said..only after driving it for 15-20 minutes...about the time i get to work and go to back in the spot..ill put it in reverse and she idles VERY low and stumbles for a sec and dies. Fires back up with no problem every time.

what i have checked...
TPS..voltage is well Within spec
IAC (actually replaced it..no change)
(ive also done the min air flow adjustment posted here) all within spec.
fuel pressure is beautiful at idle and car off key on. Also continues to hold pressure..regulator is fine.
Ive got though looking for vacuum leaks..none that i can find..all hoses appear to be in good shape

what am i missing guys? Ive seen EGR cause this under hard braking but not sure if that could be it in this case. This is driving me nuts and getting very annoying...not to mention embarrassing lol when people are shouting nice car as it dies and i have to start it back up haha..whats going on with my baby?

luvofjah

iTrader: (2)

I had vacuum leaks cuz bolts on runners / throttle body / manifold / etc... were loose...

Chevelle505

Only problem i have with a vacuum leak is that will usually raise your idle...unless im mistaken...your introducing more air the same as if you cracked the throttle..at least on a carbed motor

mcgarnicle

iTrader: (14)

When you did the min air and IAC stuff did you go through the entire readjustment procedure? Can't remember what it is off the top of my head, but there is an order to adjusting TPS, IAC, and minimum idle, and definitely mandatory when changing the IAC. There's a tech article on this site for it.

Also have you checked fuel pressure cold vs. hot or when symptoms are happening?
Have you ohm tested your injectors cold vs. hot? Looking for 12-16 ohms and you want them all in the same ball park regardless of temperature.

Any check engine codes? could also have something to do with MAF or O2 sensors.

Vacuum leaks typically cause high idle, but can also cause the motor to die, but usually all the time and not a hot vs. cold symptom. Symptoms are a little different than a carb. Any air introduced that's not metered by the MAF or data parameters is going to cause issues.

Check the easy/free stuff first and report back.

Chevelle505

All very good points! And no i havent checked injectors..that will be next now that you mention it.
as far as vacuum leaks i do see your point..thinking maybe i should reseal the top end anyway (head gaskets should be alright though..compression is good and equal in all cylinders) . Now that you mention it..Im assuming with tpi (or any fuel injection for that matter) if you adding air but the computer is controlling fuel and not seeing a demand for more via tps ect it could lean out your mixture enough to stumble the motor.
. When i checked fuel pressure it had sat about an hour after running so not necessarily "hot" but definitely up to operating temp. Ill go through injectors and get back with you. No check engine light and no codes (used my old snap on scanner)..no hard or soft codes (not sure if OBD1 can set soft codes or not...may just be an OBD2 thing). At the very least od think the pump is fine..motor off im seeing around 46lbs..running around 36 or so. Id think the regulator is subject to greater temperature variances than the pump submerged in cold fuel..ill keep checking everything else and make double sure ive got a good baseline to start from. Im still learning the TPI system and all her funny tricks..im used to a carbed big block so its a bit of a learning curve haha..even in auto school..we played around with OBD2 systems..OBD1 is fairly foreign to me.

mcgarnicle

iTrader: (14)

Yeah, I'd check the injectors for sure and smoke test the intake.

If no codes I wouldn't bother with MAF or O2 yet, although I have seen dirty/degraded MAFs cause lean conditions without setting a code.

Your running fuel pressure seems a little low. It's been a while since I had a TPI, but I think they like around 45psi at idle. Could also just be a gauge issue since it has good power and no other troubles.

I hear ya about TPI and OBD1 stuff in general having a learning curve to it, compared to the newer systems that monitor practically everything.

Chevelle505

ok pardon my ignorance but how exactly do you "Smoke Test" the intake? thats a new one on me lol.

mcgarnicle

iTrader: (14)

Pump smoke in after the maf, anywhere smoke comes out is a vacuum leak. Check you tube for some homemade units or the guy that just puffs a cigar and blows in a vacuum line
pretty handy method for finding leaks

Tuned Performance

iTrader: (92)

https://m.ebay.com/itm/EVAP-Smoke-Ma...4AAOSwYlJW52LL

mcgarnicle

iTrader: (14)

That's a really good price, I might buy one also.

A few years ago when I wanted one they were around 1000 bucks. I ended up building one out of a pickle jar, air connectors and an air regulator. Stick some cigars into it, light them and pump air through it. Ugly, but worked, sort of. This one looks way better.