toddztoyz

I have installed a MAF TPI system on my 86 Monte Carlo SS. I used the painless wiring harness with GM computer 16198259 and prom ACXT. The computer sets a code 21 (TPS sensor) and a code 42(ESC module fault). On the scanner the TPS is doing what it is suppose to. The computer sees .48 volts at idle and 4.38 at WOT. I replaced the TPS and still get a code 21 after reseting the voltages.

When the engine is off, with the key on, the MAF is showing 18 gm of flow, and the AIRFLOW is 52 gm of flow. Is this correct with the key on - enigne off? With the engine on the two values are the same. Does this sound right?

Any ideas?

dcjredline

My 89 Formula 350 is at about 8-9gms at idle never tried the scan tool with the car not running tho.

DENN_SHAH

iTrader: (1)

having much over 1 gram of air flow with key on engine off is not right, the most i have seen like that is around 2 & thats enough to sometimes cause a rich condition.
52 is about a fifth of the maximum of 255 the MAF puts out. 18 is around 15%of maximum.
i bet it runs rich & your code 21 is related to those high MAF numbers.
unplug the MAF turn the key on & check all the voltages & the ground at the MAF connector.
check the grams per second scanner readings while you have the MAF unplugged too. it will probably run better with the MAF unplugged.
if everything checks out you will need a new MAF.

Rob Wade

I thought the TPS setting was .54-.56?

toddztoyz

Actually with the MAF plugged in, it runs good. With the MAF unplugged, it runs very rich and very poorly.

I am really leaning toward replacing the computer. I think that may be my problem.

Thanks for the advice!

wulff

Me too...... I use a scanner to set mine and always try for .54 volts.

Guest

The TPS can be set pretty low, anything from .35-.6 is fine. I wouldnt worry about what the MAF reads when the engine isnt running either, I have seen all sorts of variation from car to car and scan tool to scan tool.

Check your grounds first. 42 may be from setting the timing, clear the codes and see if it resets.

toddztoyz

Yeah, the 42 was from trying to set the timing. Everytime you unplug the brown wire to set the timing, it sets that code. I did not trealize that would be the code it would set. I figured it would be something like a reference signal not found.

I can't seem to get the idle speed set. I have tried 3 times just as it is directed on this board and the idle speed is consistently going back to 1200rpm.

I am going to try to replace the computer and see if that solves all my problems.

Guest

Sounds like a potential vacuum leak.