87 Ciera rough idle after reaching operating temp.


Old 11-09-03, 09:28 AM
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87 Ciera rough idle after reaching operating temp.

I have an 87 Cutlass Ciera 2.8L multi-port injection that runs very rough after reaching operating temp. The code is reading 43, I have tried changing TPS, plug wires, vacuum was ok, fuel pressure checked out ok, EGR seems to be functioning ok. When I get on the road I am doing 60 mph but it will suddenly loose power and after a few mins I can start out and it will be fine for a while then do it again. Any ideas would be greatly appreciated.
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Old 11-09-03, 01:48 PM
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43 is ignition related from what I remember. Since it chuggles and runs rough when heated up, I'd look to the coils and modules. Have them tested.

GM DIS modules of this vintage were notorious for crapping out and giving problems.
Old 11-09-03, 02:41 PM
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The 43 code refers to Knock Sensor (KS) or Electronic Spark Control (ESC) Circuit Fault. If you are experiencing detonation then the knock sensor will send a signal to the ECM to retard the timing. This is possibly why you are experiencing the stutter condition. You could have a bad Knock Sensor. There is a process to check it but it is kinda long and Alldata will not allow me to copy. Plus you really need a scan tool, and a DVOM. Here is essentially how to check the knock sensor... Let me know if this helps and what you find out.

1. Engine Idling with coolant temp above 67 degrees Celcius.
Does scan indicate 13-17 degrees of knock retard?

Code 43 is intermittant and another diagnostic process is in order.

2. Disconnect Knock Sensor, with ignition on, using a DVOM check voltage between harness ckt 496 and ground. (Harness ckt 496 is the dark blue wire that connects to the knock sensor)
Voltage should read between 4-6 volts. Does it?

and over 6 volts, ckt 496 shorted to voltage or faulty ECM
and less than 4 volts ckt 496 is open, shorted to ground or faulty ECM.

NOTE... You are not checking the knock sensor here, you are checking the signal from the ECM.

3. Check resistance of knock sensor by connecting Ohmmeter between sensor terminal and engine block. Should be between 3300 and 4500 ohms. Is it?

Faulty Knock Sensor

Check harness and sensor connector.
If OK, Remove ECM and be sure MEM-CAL is properly seated into ECM.
If OK, replace MEM-CAL.

I hope this helps. I realize it may be a little confusing but i think it will help you fix your problem.

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