I've been trying to figure out why I'm getting an error code 33 at startup, and I broke down and got the equipment to log data and burn EPROMs. I see high g/sec Mass Air Flow values when the vehicle first starts. This probably explains the error code 33, but what is causing these values?

I also notice random bad scans of data. For the row marked in blue below, there are two crazy scans in a row. The engine backfires, idles like it has a thumper cam, and stumbles. The upper end is fresh with an aftermarket cam, but it should have a good idle. I intend to adjust the MAP tables in an attempt to fix some of these issues, but I want to have a stable base to work with. Is the ECM bad?

Here's a link to my error code 33 issue.

1989 IROC 5.7L TPI

 

What are the cam specs?


http://www.chevythunder.com/map_code_33.htm

 

Try this, pop the cover off the ECM and lay the ECM on the floor. While observing the ALDL data press on various areas of the ECM board. See if there is an area or such that can be pressed to either make the engine run better or worse. If so then the ECM is bad, if not and the engine just runs like poop the whole time, maybe not bad.

RBob.

 

You can also turn up the MAF High Diagnostic (code 33) Threshold in the constants from 45 to 60 or 80 and see if it goes away.