Chevrolet: 3.3 V-6 check engine light, oldsmobile cutlas ciera, throttle position sensor


Question
I own a 1989 Oldsmobile Cutlas Ciera with the GM 3.3 V-6 and I am hoping you can help.

A couple of months back, I was getting an intermittent check engine code.  I was told I had to replace the Throttle Position Sensor.  I did this and it fixed that issue.

Now I have started noticing the engine will cut out for a second on occassion.  This can happen while driving and while stopped waiting for a traffic light (like tonight.)  Next, I noted the check engine light blinked for a second and the mph went to zero even though I was still going 65mph.  Tonight it returned to the correct speed.  Right after fixing the TPS, this same thing happened.  When it came back on line that time, it was reading at least twice as fast and twice as many miles as normal.  Once the car was shut off and restarted twice, the doubling when away.  I checked the check engine codes tonight and the following were stored:  12(no distributer which makes sense because the engine was not running), 28, 31, and 42.

I do not know if all or any of these events are related but I thought I would include them just in case.

I could just change out the ECM but I would like a little more re-assurance this is actually the problem prior to doing that.

Any help would be greatly appreciated!

Thanks-
Chris

Answer
Sorry but I dont remember what the codes 28 and 31 are for but the 42 is probably where your problem is. It is for the EST9electronic spark timing) circuit. Normally this is always either an ECM or an ignition module. The symptoms you decribed point to an ECM because of the flickering CEL. You may be able to duplicate the condition by tap testing the ECM. Tap on the ECM with a screwdriver handle on the side with the removable cover. TAP NOT POUND!!!!