thedoctorisin

so ive been driving my 87 iroc (86 motor) for a couple weeks daily (250-300miles) and sometimes after the car is warm after i shut it off then start it again it wont hold idle. it just kind of fires then stumbles out/off.

other times the idle seems high, like the car is in closed loop operation.

im mainly concerned with the stalling issue, but im sure both issues may be caused by the same thing.

it seems like a vacuum leak but all my lines under the plenum are good, all the lines going into the TB are good, no cracked ends or anything.

***When i got the motor the top plate was taken off so i put on one i had with an old gasket i had (not torn)***

does the top plate need to have some sealant on it to create a solid seal or should the gasket be enough?

would a dirty IAC valve cause some intermitten idle issues like this or anything with the tps?

car has new cap+rotor, icm, fuel pump and filter, wires, plugs.

any thoughts or suggestions are welcome! thanks in advance!

sid rs91

check your injectors .... had similar issue and they were the cause
need to do a resistance test

Tuned Performance

iTrader: (92)

Ohm the injectors while warm as well.

dwillis

iTrader: (6)

Had exact same issue.Injectors were shorting out when warm

thedoctorisin

So Ive been driving around and it seems to do it like half the time i try to start it shut it off and start it again.

i did run the grounds from the back of the block and tapped them all together and ran a thick wire directly to the neg- cable. could that be a weak ground having a longer wire, even though its a large cable?

i can test them tomorrow, its something like anything below 10-11 ohms its no good?

i was also going to pull the throttle body off and attempt to clean that out and seal it back up so at least i know that there are no leaks coming in there.

i was talking to someone today who was asking if i checked my map sensor. i could not recall where it was in these cars. behind the dash?

the car was completely taken apart and put back together with other various camaro parts to make one nice car

Tuned Performance

iTrader: (92)

if it is a 87 tpi it is maf and you do not have a map sensor

afremont

Yeah, been there. My car would run great and then just quit on me like it had run out of gas. I replaced my ignition module, coil and finally the distributor before I did what I should have and ohmed the injectors when it was acting up.

The OPs car doesn't sound like it's quitting on him except after a warm engine restart. He also said it idles high sometimes after a warm restart. I think that sounds like the IAC could be acting up. He even said it seems like a vacuum leak, that's precisely what the IAC is. I think he should check it, clean it and make sure it turns without any sticky spots.

My experience with bad injectors was that you'd be zipping along just fine and then the engine would cut out a few times just like a carb running out of gas. Then it would just shut off for a couple of hours.

combatdoc

my tpi had similar issue but it was egr,

dwillis

iTrader: (6)

Yeah that sucks driving along then all the sudden bam your dead in the middle of the rd. I replaced my injectors with some Bosh 3's and It runs pretty great now!!I may try checking my IAC also because now after my rebuild I can be cruising along around 60mph and it'll start bucking a little like its running outta fuel.I grabbed up a fuel pressure gauge today so I can eliminate the fpr because my car sat for a while and I'm afraid that it's dried out and cracked...but I'm gonna get on that IAC right after that..something I like about this forum you may never know what you'll learn even when trying to help someone else!!

southbay08

If they are the stock multecs, although they may ohm out fine when cold,
they are notorious for coil failure when they are warm/hot.
You might want to check them both ways. If you get any reading that are 12.0 or below, then you need to replace your injectors.
The coils on injectors cannot be repaired.

AvantiHall

Do a voltage drop test on that ground you ran, connect the meter from negative battery cable to the bolt and test it. less than 0.1 volt

Then measure during cranking and should be < 0.5 volt, I always repair positives and grounds till they are less than 0.2 volts cranking

thedoctorisin

Didn't get a chance to do the ohm test but I did run the smog test at work and it was strong on the hydrocarbons and a couple others.

I'm going to clean out the TB. And try and see if the egr valve will hold vacuum. I feel like the injectors are fine. The car runs solid when its going its just this idle thing which now seems to happen when its cold warm and hot. Seems to go away after I wrap the throttle a a few good long times. I'm leaning toward the egr or the iac.

AvantiHall

post the Smog readings : Idle, 2500, or dyno 15 mph, 25 mph
CO2=
O2=
CO=
HC=
NOx=

thedoctorisin

So it was just a preliminary test, the smog tech at work was being a pain in the *** (lazy) and I couldn't bribe him with beer so he wouldn't show me how to run the entire test even though he sat and watched me for a half hour while I did an evap pressure test and just ran the sniffer in the tail pipe... People **** me off sometimes.

All measurements are off the dyno, with the car sitting, warmed up.

Nox. 0. ______ @rpm 36-250
Hc. 250-280. ______ 88
Co. 1.75. ______.20-.80
Co2. 10.4. ______ 12.8
O2. 4.7. ______ 2.3

I have a new gasket set for the plenum and runners and the TB to the plenum. Can I just use some rtv seal the lower plate and top plate on the TB? And i understand that I need to take care in removing and cleaning the iac pintel but anything in particular I should know like what not to do or what cleaners not to use?