89 L98. I keep getting 33 and 36, but the car runs fine. I've changed the MAF sensor, O2 sensor, MAF burnoff relay, and the ECM. I can reset the ECM and the light goes out for about 2 days, then comes right back, always giving 36, and sometimes (like every 3rd time) giving 36 and 33. I'm lost. What else can I try?

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89 Vette L98, M6
88 GTA L98 A4
99 Z28 SS M6
93 BMW 325i

 

May try swapping the MAf power relay as well.

I believe someone mentioned before that TPS setting can affect MAF codes...but never had an issue with my '89.

 

About 3 or 4 days ago I also got a 21, which was a TPS code. I have only seen that one once though. Maybe that is the root of my other problems. Anyone else got an opinion on the TPS having something to do with these codes?

 

Steve,

The ECM determines the correct range of intake air flows (MAF input) based on engine RPM and throttle position. The acceptable ranges account for the potential volumetric capacity of the engine at a given RPM, factored by the throttle angle (TPS). An engine at 1,500 RPM with a low throttle opening should produce a given amount of intake air. The same engine at 1,500 RPM at full thottle should flow a lot more air, so the correct input from the TPS is essential in calculating the acceptable MAF flow input.

If the TPS is improperly adjusted or failing (loss of signal), the calculated acceptable MAF flows will be incirrect. This is just another reason to adjust the MAF as close to 0.54VDC at closed throttle as possible. It is also another way to "cheat" the system into believing something that isn't real, but if you "cheat" too much, you can get caught. A low TPS voltage will contribute to a '36', since the ECM doesn't expect the measured intake air flow at the presumed throttle angle reported by the TPS.

Check the TPS circuit. Check the sensor itself with an analog ohmmeter or voltmeter to make sure it doesn't have any "dead" spots through its range. Set the TPS voltage after cleaning the TB and setting the throttle minimum air position.

 

Vader, you know more than about the little stuff than I know about the job I have been doing for 14 years! I think improper TPS setting is the problem, or it is failing all together. Please answer one last question. With my voltmeter how do I set the new TPS I'm going to buy after work today?