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Old 04-12-2012, 12:44 AM   #1
cody.freeman1
 
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1991 Camaro RS LO3 5.0 V8 Initial Start Up Rough Idle

Hi, I just recently purchased my second Camaro I am having a problem with the first 5-10 minutes after start up. It is the standard 5 speed transmission. Until it warms up after the first 5-10 minutes, you have to keep applying gas and keeping the RPM's above idle. After it has warmed up, it will no longer stall out when it is idling in neutral. It runs perfect after the 5-10 minutes. The motor oil and and spark plugs I was told are due for a replacement but was just making sure it couldn't be another problem that way I could pick up extra parts while I'm out. While I'm at it, would Synthetic oil be worth it? Thanks fellow Camaro5 Third Gen Owners, I'm going to be in both sections of the forum sections now.
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Old 04-12-2012, 06:07 AM   #2
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Hopefully IROCanSS will chime in here. He helped me out with my '91.

My list to get it running smoother;

1 Ignition control module (this will help the car A LOT) It's located under the distributor, and it's location next to the cowl makes it a magnet for condensation/water
2 new rotor / clean distributor
3 plugs/plug wires
4 Voltage on the throttle position sensor
5 fuel filter

After this it would idle smooth. But it still surges at idle and will die when I drive it until about 5 minutes go by. Then smooth and no surging/dying. Same boat you're in.

I'm getting a new O2 sensor and cold start switch that's on my intake. Not sure if yours is TPI or TBI/carbuerated.

Lastly, I need to get the car to a buddy of mine that has the software to see what the ECM is seeing. And he can tweak it.

There are so many little things that can drive you insane, but it's a lot of fun to play with. Congrats on your purchase and post up pics!
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Old 04-12-2012, 06:09 AM   #3
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Old 04-12-2012, 06:19 AM   #4
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Things to try:

-Do a full tune up. Plugs, wires, dist cap, ignition module, rotor button.
-Change all the fluids... oil, trans, coolant, maybe the thermostat. I added a lower fan sensor so it would stop getting so hot.
-Change the fuel filter. Maybe run some injector cleaner.
-Put a two wire O2 sensor in it. These cars go through O2 sensors fast anyhow. The two wire helps if your cat is not working or non exisitant. One wire is the signal, the other is a "hot" that will heat the O2 sensor at startup. If you don't have a cat, with the one wire the car is a PITA to even get started as it chokes itself out becasue it dumps a ton of fuel to it. With the two wire the car thinks its warm and doesn't flood it out.

It may need a new fuel pump/sending unit. This job SUCKS and don't cut the trunk pan, do it right! I'd try the other stuff before getting into this.

My 89 runs like a top. Fires up every time and purrs like a kitten. You just have to stay up on them. They are old and tempormental. Depending on how long the car has sat and the mileage, it may take some fiddling to get it back running good. Thats the thing with the older ones, the run better when they run frequently

Good Luck! if you have any quesitons, let us know and also thirdgen.org is GREAT!



Sending unit and fuel pump replacement:



My 89 IROC:





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Old 04-12-2012, 06:27 AM   #5
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The 3rd Gen master has arrived. No, not me ^^^him, up there.

Someone replaced my fuel pump before I had the car and did the cut in the trunk. Looks like a$$ now, but it's had a long life.
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Old 04-12-2012, 06:29 AM   #6
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I don't want to jack the OPs thread, but I have the 1 wire O2 and no cats (those were gone...... who knows when). How would you make it a two wire? I understand the concept, but what do you connect the 2nd wire to?
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Old 04-12-2012, 06:29 AM   #7
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I am no master... I am learning tho.

Then guy that tunes my 5th gen is a HUGE 3rd gen IROC and TA fan so I lean on him. He burns his own chips and eveything for the L98/LT1 cars.

Mine has a Hypertec Stage II chip but I may have him burn me one someday...
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Old 04-12-2012, 06:33 AM   #8
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Quote:
Originally Posted by garcmol View Post
I don't want to jack the OPs thread, but I have the 1 wire O2 and no cats (those were gone...... who knows when). How would you make it a two wire? I understand the concept, but what do you connect the 2nd wire to?

You can connect it to anything that is HOT when the key is in the ON and RUN possition. I forget exactly what I used, I believe it was the HOT to the distributor. I know it was right around that area.

It was amazing how differnet my car ran just by changing that. Basically my cat was shot so I cut it out. After that, car would not run right and I was afraid to even drive it. Talked to my buddy and he immediatly told me to put the 2 wire in. Fixed it.

When you car is cold, is it hard to start... like its floodded? Mine was very hard to start, once it started it ran VERY rough and smoked a lot for a few minutes, then was fine. How is yours on initial start up?

EDIT... ON and RUN may be the same position. ON is the important one.
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Old 04-12-2012, 06:38 AM   #9
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About a second of cranking then fires up. Then, another second and the RPMs start bouncing like 1500-500, up and down. After about 5-10 minutes it evens out and won't die. It very well could be the O2 sensor after reading what you describe.
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Old 04-12-2012, 06:40 AM   #10
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Quote:
Originally Posted by garcmol View Post
About a second of cranking then fires up. Then, another second and the RPMs start bouncing like 1500-500, up and down. After about 5-10 minutes it evens out and won't die. It very well could be the O2 sensor after reading what you describe.
Yup. I have to run out for a bit and I am on baby duty today but when my wife gets home, I will go out in the barn and look and see exactly how its wired up.

I remember it being very easy.
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Old 04-12-2012, 06:45 AM   #11
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Yeah, I gotta head out too. Thanks man. And, OP, get some pics in here!!
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Old 05-01-2012, 09:07 AM   #12
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have you checked the iac valve. is it seating properly? have you removed and cleaned the tbi and replaced the tbi mounting gasket? they are notorious for leaking which in turn causes a vacuum leak in which the iac cannot recover from. sounds to me asthough the iac needs to be either cleaned or replaced.

try reading thru this and see if it helps any.
http://www.thirdgen.org/tpimod2
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Old 07-04-2012, 04:08 AM   #13
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ya sounds like an IAC to me. O2's are in open loop until coolant temps are up anyways, so they wont do anything with fuel trim until coolant is over 186º. take the air cleaner off and fire it up, if it makes a varying hissing sound with the idle, most likely its the IAC. If it only starts hissing once its warmed up with your foot off the gas, its almost guaranteed its the IAC. Also, check for vacuum leaks. A fairly easy way is use starting fluid, and spray a VERY small amount under the throttle body, around the vacuum connections, etc. If the RPMS change with the spray, you have a leak. Try not to use brake cleaner, the burnt fumes are TOXIC!! Do you have a TBI or TPI car? The TPI cars have a coolant line that goes through them for emissions, and if the throttle body is cold (for the first 5-10 minutes, the IAC is probably getting stuck, the TBI gets heated from the manifold but works in a similar fashion. Let us know what you find out.

No offense to IROCanSS, but nothing on that list of "try these" will do anything to help with a cold rolling idle issue. A misfire, or no start maybe, but high varying idle is causes by air regulation. Fuel pump issues will cause a no start, or a start and stall, or no power at the top, but not a rolling idle, especially with temp change.

No sense in throwing parts and fluids into a car before its properly diagnosed. Id get my a$$ chewed if I did that at work (Im a 12 year ASE Master Tech).
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