keske968

I have a 1994 968 with 142,000 miles on it. In the last few months it has started missing when the engine is cold. After it warms up it smooths out again. I have changed the spark plugs, the spark wires, the coil, the rotor, and the distributor. It ran perfectly for about two days. Now it has started missing again. What else could be going wrong? I do not trust the dealership here to troubleshoot as I started there and everything they did had no effect on the car. If I am very gentle with the throttle until the engine is warm I can usually avoid this problem. However, if I am more aggressive with the throttle (i.e. 3500 rpms) it will start to miss after about 2-3 minutes of driving. Any suggestions?

keske968

I suppose that I should add that the wires were changed about 3-4 months before the rest of it was done. Is it possible that I had a bad coil that fried a wire?

odurandina

computer/O2 sensor related? ? ?

keske968

Not sure. The dealer cannot come up with any fault code. Which computer would it be?

ninefourfourt

Double check the dist cap to make sure it has no visible cracks in the plastic. Use OEM style plugs, stay away from those 'cool' quad tipped bosch units.

Possible fuel issue (fuel injector) or vacuum leak could be the issue too. Its definately harder to track such things down on an older non-OBDII car.

keske968

Dist cap is new. Could be the plugs I am using the bosch quads right now. I just find it wierd that when I changed the wires it ran fine for a day or two same with the new dist cap, rotor, and coil then it started missing again.

John Etnier

Still: check the distributor cap. Pull the black shroud away from the red bakelite body to look for carbon traces.

968rz

A garage should be able to scope the ignition to see if there is an electrical miss but my quick guess from your symptoms is failing head gasket or leaking injector (maybe a vacuum leak, I've seen them happen only when cold).