I have a 1994 Olds 98 3800, V6, 78k miles. The engine runs very nice for about 20 min. then the engine jerks the check engine light comes on and the engine stalls.If it restarts, one cylinder misses.If it will not restart right away it will start after engine cools.The car does not over heat. The computer codes the Cam sensor.For the past seven months a Machanic Has been replacing many parts without curing the problem. He has replaced the Computer, Cam sensor,Air flow sensor, Harmonic balancer,Timing chain and gears, Ignition control module and checked out the wiring cables. I would like to have my car back, repaired. Please help with this problem.
Boy! He sure shotgunned a lot of parts at this problem. But nowhere do you list replacing the Crankshaft Position Sensor. A defective CPS can cause the problems you describe.
Tester
I have made contact with the Mechanic. He said that He has also installed a new crankshaft Position sensor. Please continue to Help with this problem. Thank you.
If the mechanic hasn’t checked the input power to the ECU and ignition areas when this trouble happens it would be good to do that to make sure that is ok.
I would be checking and comparing signals to the ECU before and after the trouble using a scope to see if something shows up there.
Check one other thing. The positive battery cable.
The battery on your vehicle has the side mount type battery terminals. Under the protective rubber cover of the red positive terminal corrosion can form. This can cause a voltage drop to the power distribution center. When this happens, the voltage can drop where the ECU cuts out. And when this happens, the engine shuts off.
Have your mechanic remove both terminals from the battery, and then peel back the red rubber cover that protect the positive terminal. If a white/greenish powder substance is found under this cover, replace the positive battery cable.
Tester
I notice that the mechanic did not substitute or replace the coil pack. Also there usually is a power relay for the PCM and engine power. It may be labeled under Automatic Shut Down relay ASD.
This problem seems to be heat related. One way to troubleshoot this sort of problem is to get the problem to appear and then use a cooling spray to cool the suspect part(s) i.e. ignition control module, coil pack, CMP, CKP, ASD, etc. Try to determine which part when cooled allows the engine to restart.
Very good suggestions Researcher. You may have the answer for this problem. The shut down relay would be top on my list to check and then the coil pack.
The Positive battery cables have been replaced. Now the car will run for about 50 min. before the engine dies. replaced the coil pack but no change. Can not find an Automatic Shut Down Relay in the parts list for this car. Could it be called something else? I appreciate your help. Please input any ideas.
Thank you