Hi i am new to this site and 3rd gens. My 89 camaro Rs has a 2.8l v6 in it and its been misfiring for the last 4 months. When its cold it runs fine but as the engine gets heated up its starts to misfire the more i accelerate. I have changed out the spark wires, spark plugs, and recentely the entire distributor. I have also replaced the TPS and the IAC. does anyone have any idea on what could be causing this problem? When we try to read the codes it says everything is fine but clearly it isnt.

 

Any time you get a new vehicle it is a good idea to run some basic tests before throwing parts at a problem. Run a compression test and see if all the cylinders are faily close in readings with none below 100. Check the timing 10 BTDC with tan wire disconnected. Put a vacuum gauge and see if it has steady reading around 15. Check the fuel pressure using the test port in the rear of the plenum.
Get a factory service manual and follow the trouble shooting charts. The manual can be found on CD on ebay or amazon for about 35 dollars. It will pay for itself in no time.

Unfortunately our cars can often run poorly without leaving codes. You may see the check engine light while driving but nothing but code 12 when checking for errors.

Were the old plugs in bad or good condition?

 

If it's fine when cold then it's prob on of the temp sensors not giving the right info to the ECM. Possibly staying in open loop and not going into closed loop when warmed up.
Apart from that I had a vacuum leak last year giving me a missfire , right around the upper intake manifold, took me ages to find it , make sure everything's bolted down properly.

 

I ran a compressor test and everything was fine. i have had the car for two years and just started acting up back in January. It did clear up for about two weeks after i put an ignition coil and fuel filter on it. But then misfired again. some days it runs perfect and some days its ruff. Could it be in my fuel system or O2 sensor?

 

Also the old plugs were bad. Also when i replaced my wires with 7mm they got burnt through real quick. ended up putting 8mm on and they are still holding up.