Questions and Answers

Caprice Classic EGR Problem Q. Vincent, I hope you can help me. By the numbers: 1. 1991, Chevy Caprice Classic 2. 305 throttle body fuel Injection 3. Automatic Transmission 4. 138,000 miles 5. Throttle body fuel injection 6. ABS 7. Power steering, power brakes, power locks, cruise, cold A/C 8. Rack and pinion steering

This car has a strange problem that I can never duplicate at will. It runs fine 99% of the time. But every so often after it has been running for a while a problem occurs. As I come to a stop the engine acts like it is missing or wants to die. It drives and runs fine until I slow down. If I put the transmission into neutral and hit the throttle, the engine revs up just fine. It will shake act like it is missing until I start moving again.

Then it will run fine for many miles. This only happened once in a great while but now happens about once or twice a week. Then the problem won't appear again for several weeks. I have replaced the cap, rotor, wires, plugs, PVC valve, air filter etc. It has only died on me once and started right back up without a problem. This problem has only once happened to me in my driveway. I let the car sit acting like it wanted to die but it never did. Increased throttle without moving the card did not solve the problem.

I turned the key off and immediately restarted the car and the problem was gone. The only error code in the computer was for the MAP sensor. But this could be a "false" code because of the rough idle causing the air pressure to be wrong.

My thought was that it might be a sticking EGR valve as fuel and ignition seem fine. I figured the EGR might be sticking open causing a lean mixture. But how do I go about testing this theory?

If it matters, I had to replace the O2 sensor about 5,000 miles before all of this started happening because it physically broke. Any suggestions?

Thanks in advance,
Tim

A. You could be correct about the EGR. You will need to spray some carburetor cleaner around the pintle valve when it does it's thing to be sure. It should run okay if it's leaking and you spray it. At this mileage, I would replace it and the EGR solenoid if it's the problem.