I have a 95 Z28. When I start up in the mornings it runs really rough. I can feel it popping in the gas pedal and it hesitates really bad. After it runs a little bit it suddenly runs good. It seems like when it gets to a certain temp it fixes itself. I read that I have heated oxygen sensors in this car. There was something to do with 600 degrees F and the O2 ensors. Could the heaters be bad? COuld the charcoal canister be clogged? Im lost!!!!!!! Please Help!!!!

 

Take a look at ECT sensor (engine coolant temp sensor (2 wire), not the the temp gage sensor (1 wire), and the IAT sensor (intake air temp sensor). They may be bad and giving wrong data to the PCM.

 

ok... I checked the sensors that you suggested and both were good. Could the heater on one of the oxygen sensors be bad?

 

I was just reading your response to a question about removing the AIR pump that someone asked and something you siad caught my attn. You said that the AIR pump is meant to warm up the O2 sensors; well the only time that I have this problem is when that pump is running. When it shuts off the car runs and responds fine. Would the pump be bad or the O2 sensors? How can you tell if the pump is bad?

 

Is the check engine lite coming on? The PCM does not look at the O2 sensors when the engine is first started, it only uses the sensor data when it goes into closed loop. You can use a scan tool to see what is going on with all your sensors. The pump does nothing with the O2 sensors, its purpose is to feed air to the cats to make them light up faster. Fuse #11 provides heater power to the O2 sensors; however a bad heater will set a DTC and light the MIL lamp
How did you test the temp sensors?
How it works:
When the engine is first started the PCM looks at the ECT, MAP, MAF, TP sensors, and clocking info from the optispark.This is the open loop condition. The system stays in this condition until the ECTreports a certain temperature, the O2 sensors start working, and the engine has been running for a predetermined length of time. When these conditions are met the system goes into closed loop and the PCM looks at all the sensor data.

 

The check engine light is not coming on. When the car is at an idle in the mornings or when I first start it up after it has been sitting a while , it idles fine. Its when I give it the gas; thats when it starts acting up. I tested the temp sensors with a volt meter.

 

You know, I think I had the same problem. WhenI would start the car in the morning, it would run rough until it's been run for some time. It started getting worse and would run rough longer in the mornings and would also run rough after the cars been off for about an hour.

It doesn't do it anymore and this is whatI found and changed while installing long tube headers:
#7 spark plug housing was broken in half!(I'll try and post a pic)
oxygen sensor on the passenger side was BAAAADDDDD!!!!!

That's whatI changed, everything else like the other 7 spark plugs and wires went back in the same.