I read through the archives pretty thoroughly (so I think) and found a few people that have a similar or same issue as I am having. (code 33 is high gm/sec)

This is going to be lengthy, but hopefully this will help eliminate as many follow on questions as possible.

I've got an autoxray 240 scanner that I'm using at this point, but winALDL is coming soon, just need to get the laptop setup for it. Burning equipment will be coming shortly.

It's a new (rebuilt by me) 355/manual trans with Vortec heads, pretty much stock Firebird induction (the tubing from air cleaner to MAF is same as factory, except slightly longer distance from air cleaner. 90* bend after MAF), roller cam with .454" max lift/112* LSA, roller rockers, and headers. TPI is minus the cold start injector. ECM is '165 with ABWB. (305 manual trans car)

Code 33 is CONSTANT. I followed the flow chart in the service manual, and the results of that were wrong. (conclusion was a break in one of the circuits, there is not, checked with multimeter) All other tests in that chart "prove" the MAF being good. This test includes the wiring for the MAF, and the MAF relay as well.

From what others posted as a fix for this issue (seems to happen typically on larger or modified engines) raising the gm/sec for startup from 45 to 55, (or more) solved the problem.

I have set minimum idle per the technical article on this site, and the code persists. Checked for vacuum leaks (with propane) just to ensure that was not any sort of factor, although it didn't seem likely. No leaks found. "Base" timing is 4*, knock counts are very rare from what the scanner shows, driving, increasing/decreasing RPM at idle, etc.

Scanner indicates 2000+ gm/sec at idle, which increases progressively (4-5000) as I get into the throttle. I've changed the closed throttle TPS reading from .54 to .60 for testing, no difference. After clearing codes, code 33 returns 2-5 seconds after the engine is started.

Engine runs good, all readings through scanner seem to be "normal" except the gm/sec reading being so high. I speculate this isn't really the cause of the code since the reading does change in proportion to throttle, and the MAF "checked out" through the service manuals diagnostic tests I followed. Fan 1 is on constantly, I'm assuming this is part of the "failure" that is typical to "save" the engine when certain things go wrong. The fan running constantly (regardless of engine temp/ECM command)isn't 100% though...a couple of times the fan DIDN'T run, but the check engine light was still on. Even when fan1 is on (below temp threshold of the ECM) the scanner shows fan1 is off.

Is raising the gm/sec the right way to go about this? Without seeing what I believe are the "actual" gm/sec, I don't see how I can prove the engine is ingesting more air at startup than the ABWB is expecting. Is there something else I should be looking at that is more basic (or even more complex) that perhaps I have missed? Or is using the ABWB a this point capable of causing me enough issues (too many differences introducing too many variables) that I should just "start over" with say, the APYP, and see where that gets me? APYP is an '89 350 vette manual trans IIRC.

 

After more archive searching, another has seen 2000+ gm/sec with the autoxray without throwing a code 33, so that is probably an autoxray issue.

UPDATE: Well, this has been a long time coming. I fixed this problem awhile back, and this popped up in a search today I was doing, so I figured I should fix this for future searchers.

A very wise person told me that I should follow the flow chart yet agian, in case I made a mistake, and sure enough, I hadn't tested a wire correctly. With the factory flow chart, (again) I was able to "prove" it was a bad MAF, and luckily got a great deal on a known good used one. FWIW, the wells MAF that is recommended here I had a VERY hard time finding, and actually couldn't get one locally at all.

Anyways, threw the known good MAF in there, code went away. Have had a couple of times where the vehicle just died when I let off the gas, which is how it acted with the previous bad MAF, I suspect I need to go in and make sure all the MAF connectors are tight.