camaropower88

I have a 1988 Camaro IROC-Z with the 5.7 TPI. It is all stock except for flowmaster 80 series cat back. It idles with a lope, like a big cam or something. I absolutely cannot figure out why. Also does not like cold starts, this whole problem started in the winter (20 degrees?) it would start, RPMs come up and then it would chug and stall seconds after. Thought it was the weather. Well now its 80 degrees and its even worse. I have tried everything to fix this problem, and nothing has worked. I have put in the following parts:

fuel filter
cap
rotor
plugs
wires
intake gaskets
fuel pump
fuel injectors
EGR valve
EGR solenoid
MAF power relay
swapped MAF off my dads 88 5.0 TPI
Let alone countless idle air adjustments/TPS adjustments.
I have sprayed all around with carb cleaner to find nothing. unplugged each vacuum line off the plenum one by one and plugged it with no results. I am loosing my mind. Can somebody give me any ideas??? I need help!!!

camaropower88

anyone?

elpulpo

well you covered lot off it ,have you tried the iac valve
make sure there is no carbon residues (clean throtle body),any codes?also check the maf burn off relay if code apear and clean the maf sensor with maf cleaner,check fuel pressure 40.5-47 psi turning key on only it should hold when pumps stop.

elpulpo

check tps adjustment 0.54+-.08

camaropower88

Thanks for the replies!! I have cleaned the IAC twice, cleaned the throttle body and intake manifold, plenum and runners when i did the gaskets, cleaned the MAF. My fuel pressure was 30 PSI at idle before the fuel pump so thats why I put a pump in it. TPS is at .56V...I'm just completely stumped. Is there some hidden HVAC vacuum lines that i should check??

luvmy64

Could the ECM be bad, maybe? Or the ignition control module?

camaropower88

I was thinkin ECM but how would i know for sure its bad? Not sure if this will help anybody but i drove around this morning with the IAC and TPS unplugged and it idles flawlessly except it idles a tad high like 800 RPM or so.

camaropower88

also with one of em plugged back in and the other unplugged, idle is a little lopey, only idles perfect with both of em unplugged.

elpulpo

check ignition timming,ECM ground circuits,PVC valve for proper operation,check air system there should be no air while in closed loop,check for fuel in pressure regulator hose,also try only disconnecting the maf sensor and note any changes,fuel pressure after fuel pump replaced?

luvmy64

What you did was put the ECM in "limp home" mode. If its not a sensor, then it may be the ECM...

flu_by_u

I was seeing the same thing on my 5.7L TPI bird. It ended up being the MAF sensor. But someone also told me to check the Knock sensor, knock sensor module. Hope you figure it out.

camaropower88

I put it in base timing and set it to 6º BTC so i know the timing is good, i unplugged the hoses on the AIR so i know there is no AIR in the exhaust in closed loop, no fuel in the vacuum line for the FPR, and no change with MAF disconnected. How would I check the PCV system to see if its working properly? Besides the old rattle test (which it does rattle)

burnout88

I think you need to do a compression test on the motor. There may be something bigger going on here.

lunaticinaZ

Even with cleaning the IAC that dosent ensure it works correctly, it could be bad. And when you set the tps, Did you check the voltage from idle to WOT to make sure the voltage rises steadly and constant?

Also are any of the plug wires sparking on anything or touched something and has a burnt hole in them?

Also try wigling the connecters on the ecm while the car is running. If it changes the idle it could be the ecm.

3rd gen Will

iTrader: (8)

My car acted similar to that when I had a broken injector ground. The #2 injector wasn't firing, it would run weird, had a "lope" didn't want to idle when it was cold.

I'd check continuity on all injector wires to the PCM and make sure you have 12v on the pink/black wire at each injector connector.

One think I didn't see on you list was the Ignition coil. have you checked the resistance in it? if it's out of spec you will get a weak spark and also cause the car to run crappy, especially under loads.

camaropower88

thanks guys for all the responses! lunaticinaZ I have checked the voltage on the TPS .54V at idle and 4.5 at WOT but i did NOT however see if it rose steadily and constant...good idea! How can i be sure the IAC is at fault? I took it out and watched it move in and out but i dont know guess it could still be bad. Tried wiggling ECM connections with no luck and the plug wires seem to be in tact. Will, I have put a scope on the secondary ignition and the patterns looked pretty healthy, although it wouldnt hurt to check the coil resistance anyway...what do i have to loose?! Would you happen to know what the Resistance should be? Also going to check the injector wire resistances..another good idea! Thanks a lot guys. Also got a code 43 today, i know the knock sensor has been unplugged for a while but i get a code now? this sound right to anybody? haha something isnt right

elpulpo

check the resistance across iac coils should be more than 20 ohms between iac terminals opposite harness connector terms "A" TO "B" AND "C" TO "D"

Rod Behring

If it idled good with the IAC disconnected, you found the problem. The IAC must be bad. Cleaning it won't help, you'll have to replace it.

3rd gen Will

iTrader: (8)

Coil test from the 1991 GM Service Manual

Crude rendition of a coil, sorry can't find my camera or I'd take a pick of the page for ya.

__0__ Coil wire
..- - 1 Connector
..- - 2
..L R

Test from 1L to ground resistance should be infinite (open)
Test from 1R to coil wire use high scale, should read high but not infinite
Test from 2L to 2R should read very low or zero, but not open.

Hope this makes sense for ya, I prefer to test the coil hot, let the car run for a bit if you can since resistance goes up with heat, that gives you more of a realistic idea of what is going on with the coil when you are driving.

burnout88

Code 43- This code is related to problems with the esc system. The code is usually set when there is a voltage detection of the wire going to the esc module to the ecm pin B7. The code will set whenever the engine is first started, and the ecm checks the function of the esc. Also once engine operating temperature is reached and the throttle is nearly open, the ecm will advance the timing until pinging is heard and then back off the timing. If the ecm does not detect the knock sensor operating, it will also set a code.

Pat1990GTA

Im having the same problems..
Weird rough idle almost like a slight missfire or somthing?
Hard starts lately.. longer than normal cranks, If i crank it for a few secs and it doesnt start up.. i try again right after it starts right up. It use to start up right away first try =(
Im wondering if its the injectors? they are some sort of orange aftermarket ones and they all have about 18 ohms of resistance

I really want to track this problem down!

soon

Replace the O2 sensor, do you know if it is going into closed loop when you start it? simple to replace, how do your spark plugs look? are they fouled at all?

camaropower88

ok so with the IAC disconnected it idles good, doesnt even stall on a cold start. Im going to make my own ALDL cable and get winALDL so i can do some datalogging. I replaced the o2 sensor about a year ago cause it was dead. The Spark plugs look OK, my leaking valve seals dont help a whole lot(damn SBC's and thier crappy seals)...but they have been that way for a while and this car used to run really good. And Will i give you props, thats a pretty good coil haha. Pat1990GTA, when you start the car can you hear the fuel pump kick on? If not, i would look into the F/P relay. If the relay is bad it can cause hard starting because as a back up for the F/P relay is an oil pressure switch that will only send power to the F/P only if oil pressure is greater than 4PSI (need to crank a lil longer to build the oil pressure). Might also wanna check your MAF or your coolant temp sensor?

3rd gen Will

iTrader: (8)

haha, thanks it made sense to me, I am assuming the coil checked out or did you not test it yet. Re reading this thread it does sound like and IAC issue, the engine will pull timing and dump fuel to get the idle where it want's if the IAC counts are maxed out either direction. Which will cause weird things to happen.

watajob

iTrader: (29)

Have you checked for a vacuum leak at the butterfly shaft? Common issue and will cause a lousy idle.

Pat1990GTA

Fuel pump comes on right away.
I took the fuel pressure regulator line off it was dry, but it smelled like fuel? I tried to put vacume to the regulator to see if it was leaking and the vacume didn't drop
The IAC looks new like it was replaced by the previous owner.. but maybe its gone bad?
I'm thinking coolant temp sensor? or Leaky injector? somethings not happy

Pat1990GTA

I did hear somthing about these thorttle bodies leaking and causing problems? Is there a way to check them? Before i drop $200 on a new one lol.

camaropower88

I'm pretty sure all my issues are due to faulty wiring to the IAC or faulty ECM. I measured the coils on the IAC. A to B were 60 ohms and C to D was 55 ohms. Ignition on engine off i jumped the A and B terminals on the ALDL and put a test light to ground and put the test light on each IAC terminal connector..not a damn light on any! Nothing at all...what are the odds of ALLL of the wires having a faulty connection or having an open somewhere?? I'm thinkin the ECM is being stupid haha

camaropower88

also only getting 5 volts at IAC connector terminals...its supposed to be 12V right?

camaropower88

another update, ohmed out the wires from the ECM connector to the IAC connector...all ohmed out to .2-.3 ohms. Could it possibly be the ECM? and if it is...why? what would cause it to go bad?

3rd gen Will

iTrader: (8)

5v at the IAC is correct. .2 .3 is fine, you had continuity through the wires thats the important part. the ecm is an electronic peice. heat vibration etc cause things on the board to fail. broken solders on the board arent impossible

camaropower88

might just put an IAC in it and see what happens, it will still start and stall in the morning but not as bad with the IAC unplugged. Has a terrible hesitation to almost the point of stalling when its cold. Once it warms up with the IAC unplugged it idles and runs perfectly

lunaticinaZ

My is that may just very well be your problem. They aren't to expensive and if by chance it's not the problem..... well you know it's not the IAC lol

camaropower88

I hope its the IAC,tired of workin on this thing and spendin money on parts just want this issue to be resolved! And I called a local GM parts place around here, 95 bucks for an IAC!

lunaticinaZ

wow I got mine at auto zone for around 50

camaropower88

I heard that people have gone through a few IAC's from other places until they finally got a dealer IAC and it worked perfectly, not sure how accurate this is. But **** if this one lasted me 23 years, the new one should last a long time too!

3rd gen Will

iTrader: (8)

I got a Delphi one from Rock Auto for $57 ($60 shipped using the discount code) about 2 weeks ago, they were on clearance, they said they had 6 left when I bought that one. I figured Delphi makes stuff for GM and AC Delco so the quality should be just as good as the AC Delco one for $87.

camaropower88

Well, IAC and another minimum air adjustment helped, seems to run better part throttle, cruise, and WOT, but still has a rough idle, not as bad but still not fixed. Any other ideas? Coolant temp sensor? I'm really getting frustrated at this point.

3rd gen Will

iTrader: (8)

There is a thread on here somewhere about the approx resistance in relationship to temp for the CTS. or you could use a scanner to make sure the Eng Temp is correct. Or you could just swap the sensor, I am personally not a fan of throwing parts at a problem.

camaropower88

Well, CTS resistance in the morning was .622K ohms, which is 622 ohms...according to the chart i found on Mitchell, Thats near 160ºF . Cause 160ºF is equal to about 450 ohms. Now I guess on the planet Mars it might be 160 in the morning...but, not on earth

3rd gen Will

iTrader: (8)

Sounds like a good possibility that your CTS is bad then. You can always go to the parts store and ohm out a new one and see what the reading is for a double check.

camaropower88

Ok well i took it out and it was a lil gunky so i cleaned it up, re checked the resistance and its OK. Reinstalled it but still no difference. I was playing around with my ignition timing and the idle was getting a lot better. But it doesnt like 6 degrees BTDC which is the spec. On mitchell it said to set the timing the EST needs to be disconnected (duhh) and the car must be at a low idle, 400 RPM and transmission in DRIVE and then set the timing to 6 degrees BTDC...? Is this correct? If so this could be my whole issue being that my timing was not set "properly.

elpulpo

Look at the emission label on the hood,,,,,, if is any other ways yes!!!!! The est is got to be disconect or the timming wont be right.

elpulpo

Normal idle runs between 600-700 rpm so 400 is lil low

camaropower88

yeah I wonder about mitchell and the information that they supply sometimes. I always disconnect the EST before playing with the timing. On the emissions label it does say however, timing must be set at 6 degrees BTDC with transmission in DRIVE. Not at a specific RPM though. Might give this a try and see if i can get the timing right. Or if playing with the timing was just merely covering up another issue.

jjlabinski

the 400-450 idle is with the IAC closed and disconnected.
When you plug the IAC back in it will add the additional idle air which will bring your idle up to around 650.

camaropower88

Ah i see. I'll have to try to set the timing at 6 degrees BTDC with EST and IAC disconnected at 400-450 RPM then. Hopefully this will fix everything, Cause i know for a fact that the timing isnt right and that means the idle air cant be right either. Also, jjlabinksi would you happen to know if the timing and idle air need to be set with the trans in drive?

jjlabinski

that is what is recommended but I feel it unsafe if you work by yourself.
If you got a buddy have him hold the brake in gear while you make the adjustments and dont stand in front of the car when it is in gear!

camaropower88

well, I got the timing and the minimum air idle adjustment back to spec's. Idle still sucks, if not worse. I'm at a complete loss, I do not even know where to go from here. Anybody else got any ideas? I HAVE to be missing something VERY stupid. About to throw a carb on this thing and call it a day.

camaropower88

Ignition coil tested out OK.