Jim Grant's Tech Tips

90 Chevy Cavalier, Engine Knock
Q: The problem I'm having with my '90 Chevy Cavalier is that after driving about 5 miles, the engine begins to knock and quits. After putting the car in Park, I can immediately re-start the engine and it purrs like a kitten, but as soon as I put it back in gear the engine knocks and then quits. I can let the car sit for a few hours and again can make it about 5 or 6 miles before this happens again. Is this a bad transmission or could something else be the problem.

A: It's possible that you have automatic transmission problems, but I wouldn't replace it without further diagnosis. One way to eliminate an automatic transmission related noise from the engine, is to unbolt the torque converter from the fly wheel (flex plate) and then start the engine. Ideally, have the engine up to operating temperature with the problem at its most persistent point. Unbolt the torque converter (there is room enough to push the converter away from the flex plate) then start the engine to see if the noise is still present. Also, be aware that flex plates are known for cracking. A cracked flex plate will make a fierce and sometimes erratic knocking noise which sounds like a bad transmission or engine. Changing the transmission in your vehicle is costly and not a simple task; be sure to have it diagnosed correctly before replacing parts.