1991 Buick Regal code 22 & 34 - runs rough

[mdowdell]

This problem showed up all of a sudden on the freeway. Its intermittent in that it does it 90 percent of the time but for no obvious pattern will vanish sometimes for about 5 min then return. When it first started the problem only existed from 50% throttle to almost full throttle where you could sometimes drive through the rough spot. Below 50% throttle was generally ok. The problem is getting worse now and exists from idle on up to full throttle but still intermittent since every so often if corrects itself for a few minutes. still, 90% failure rate. The problem resembles a spark miss, has a jerky and erratic pulse of misses - the overtone of the engine as a whole feels good behind the misses and still has power between the misses. So far, no backfires.

My first feeling was that it was a faulty fuel filter or fuel pump, but after driving up the rpm range and driving through the sputtering with higher rpm with regular success, that eliminated that as being the problem. I then suspected the TPS or MAF as culprit, or possible the ignition system. After pulling the codes I have focussed on them instead.

The error code 22 points to the "Throttle Position Sensor(TPS) or circuit voltage low". I ran an ohm meter on on the TPS pin outs and verified a smooth and gradual ohm change from closed to full open throttle which leads me te believe its ok and probably a result of something else since the problem was only 50%-80% throttle when I checked.

The error code 34 has 2 possibilities:
1. "Manifold Absolute Pressure (MAP) sensor signal voltage low"
2. "Mass Air Flow (MAF) sensor signal - low airflow indicated"

I was going to pull a vacuum signal off the intake and see if anything was obvious but I'm not sure I will get any definitive results. All the plug wires and plugs are good, verified spark as well so I feel semi ok there. Any thoughts on how to check the error 34 would be apreciated as well as other thoughts on the problem.

- Mike

[RABarrett]

I strongly suggest the possibility that the air flow meter be thoroughly checked. These codes relate to the incorrect relationship between the throttle position sensor, the airflow meter and vehicle and engine speed. These airflow meters were a problem for GM since their introduction. I do not advocate simply guessing at the cause; parts are expensive. I do suggest getting the airflow meter properly checked, and expecting a bill for the same. Ray

[dssreed]

My car did the same thing I finally ended up replacing a bad wiring harness near the crankshaft and the Engine Control Module. I also replaced a lot of other parts but I think now they may have been good just getting bad signals because the ecm was bad.

Originally Posted by mdowdell

This problem showed up all of a sudden on the freeway. Its intermittent in that it does it 90 percent of the time but for no obvious pattern will vanish sometimes for about 5 min then return. When it first started the problem only existed from 50% throttle to almost full throttle where you could sometimes drive through the rough spot. Below 50% throttle was generally ok. The problem is getting worse now and exists from idle on up to full throttle but still intermittent since every so often if corrects itself for a few minutes. still, 90% failure rate. The problem resembles a spark miss, has a jerky and erratic pulse of misses - the overtone of the engine as a whole feels good behind the misses and still has power between the misses. So far, no backfires.

My first feeling was that it was a faulty fuel filter or fuel pump, but after driving up the rpm range and driving through the sputtering with higher rpm with regular success, that eliminated that as being the problem. I then suspected the TPS or MAF as culprit, or possible the ignition system. After pulling the codes I have focussed on them instead.

The error code 22 points to the "Throttle Position Sensor(TPS) or circuit voltage low". I ran an ohm meter on on the TPS pin outs and verified a smooth and gradual ohm change from closed to full open throttle which leads me te believe its ok and probably a result of something else since the problem was only 50%-80% throttle when I checked.

The error code 34 has 2 possibilities:
1. "Manifold Absolute Pressure (MAP) sensor signal voltage low"
2. "Mass Air Flow (MAF) sensor signal - low airflow indicated"

I was going to pull a vacuum signal off the intake and see if anything was obvious but I'm not sure I will get any definitive results. All the plug wires and plugs are good, verified spark as well so I feel semi ok there. Any thoughts on how to check the error 34 would be apreciated as well as other thoughts on the problem.

- Mike