I own a 1991 Chevrolet Camaro Z28 with a 5.7 tuned port injected motor. I previously had an SES light problem and it was the EGR solenoid and EGR connector. The car ran well for two weeks and now it's giving me a severe rough idle and miss to the point the car is shaking and making the rpms in the car fluctuate. Every time I come to a stop or when it's in park I have to keep my foot on the gas to rev the rpms up to prevent my car from stalling. The exhaust smells of gas on cold start . When its warmed up, it smells like rotten eggs. Has anyone experienced this before? If so, what have you done to correct the problem? Your response is greatly appreciated. Thank you.

 

How long since your last tune-up? If it has been a while that would be a good place to start. Change everything; plugs, wires, cap, rotor, all filters, pcv, O2, ect. Check everything; timing, tps, iac, vaccum, ect. After all that is done reset your ecm, drive it for an extended period of time (couple of days or 100 or so miles) and then check for codes. If these parts are all up to date just check for codes and reply with your findings unless you know where to go from there.

Info on accomplishing any of the above can be found with a search, if not reply back here with exactly what you need more info on.

Good Luck!

 

I have changed the dist. cap, dist. rotor, spark plugs, egr solenoid and connector,and egr except for spark plug wires, oxygen sensor, iac valve, and tps. Btw, I changed the thermostat two days ago from a 160 to a 195. I am using dexcool antifreeze. I will have to change the spark plugs because they are probably fouled by the excessive surging and missing.

 

Your description and symptoms sound like a significant vacuum leak. Are you sure the EGR is the right one for your engine? Negative backpressure pilot valve, and all? You can try removing and plugging the vacuum line to the EGR to be sure.

You can also remove and cap the PCV, brake booster, and HVAC vacuum lines. Check the plenum. TB, and runner gaskets. Don't overlook the injector 'O' rings as a potential vacuum leak.

 

SteveZ28:

I have a 1991 Z28 and I had similar problems with the rough idling. I replaced the egr, egr solinoid, complete tune-up, and o2 sensor. The rough idle was still present. I then took it to the dealer and they discoverd that the cause of the rough idle was due to an ignition breakdown. They replaced the entire ignition system and that took care of the problem.

Hope that helps.

Good luck!

Benny

 

Ok. The the spark plug wires and oxygen sensor have been replaced. A code 44 was reported from the SES light. The iac was tested and was fine it was replaced seven years ago. The car does not idle as bad as before, but it is still idling rough when in gear like at a stop sign or in park. When it takes off or on the road it runs fine and it has even been put on an emmissions dyno and it the emmission readings are good and is in closed loop mode but when I put slow down it goes into open loop and starts to miss. Everything has been dismantled except for the intake manifold base plate. The fuel injectors have been taken off the fuel rail. How can I tell the fuel injectors are bad? How do I do a fuel injector to see if it clogged? I also found out my fuel pressure regulator is in need of replacement. Should I get an aftermarket or orginal equipment from GM? Compression is good on all cylinders. I just don't know why it performs well on acceleration or cruising speeds but it doesn't perform well on idle? Any ideas? Your responses are greatly appreciated. Thank you.

 

Have you changed the fouled plugs yet?

You can get an idea about the injector condition by performing a power balance test. However, since you have determined that the FPR is faulty, you need to replace that to restore proper fuel pressure before you proceed. That alone could solve a few of your problems.

Most of the popular aftermarket replacement FPRs are NOT a complete unit, but are simply an adjustable regulator conversion kit. They require you to use the existing base, and if the regulator problem that you have diagnosed is in the valve disc or seat, the replacement parts will not repair the problem. Make sure you get a complete regulator. Install it, then set the pressure to 37 PSIG at hot idle with the vacuum line connected.

 

the rotten egg smell is usually a bad catalatic converter, so keep that in mind too.

 

Ok Tek Viper I'll keep that in mind. The catalytic converter doesn't have to make a rattling sound for it to fail, correct? It will probably started to turn a yellow color on the cat converter shield. So I have get under the car and inspect it for color change. Any other things to look for in a cat? Vader, I changed out the spark plugs they were black. I have decided to get a complete fuel pressure regulator but I don't know if I should get it from a local auto parts store or at the dealer. By the way all the fuel injectors are going to be replaced because three injectors had low ohm readings especially on cylinders 2 and 4. The cylinder 4 injector leaked. The cylinder 2 injector was spraying more than the rest so that is what led me to my decision of replacing them all. You don't suppose this might be something electrical that is going wrong causing this rough idle, so that I can start exploring in that area.

 

The car is fixed, only thing is that when I start it up whether hot or cold it revs very high. First of all, the heavy engine miss, rough idle was due to the fuel injectors and now car is idling smooth and the power is back. But everytime I tap the ignition the rpms skyrocket to 2400 rpm or higher possibly because my tach doesn't work too well and stays there for 2 seconds and comes down to approx. 1500 and stays there in Park. When I shift it Drive it drops to 1,000 rpm. I have had this happen before and it was the ECM. But this case seems different. The ECM couldn't have failed again, could it? Any ideas out there? Your responses are greatly appreciated. And thanks for all of your previous responses. Thank you.