ive read through all the archives and tried everything except putting in an aftermarket chip to get rid of my code 33 in my 87 trans am with a 305 TPI vin code F including:

-new MAF sensor
-new MAF relays (power and burnoff)
-new TPS
-Adjusted TPS by sticking things between it and the lever on throttle and by turning actual sensor (now at .62 volts on idle)
-checked all wiring from sensors to relays and to computer through firewall
-New ECM
-went through all diagnostic steps in the shop manual

i am still nowhere, the car will either start with the SES light on or drive for awhile and after stalling or severe uneven throttle (without touching pedal or while holding steady car revs drastically) the light will appear and upon shorting ALDL i get a code 33 and every now and then 33 and 36. has anyone found a fix to this problem other than buying an aftermarket PROM which some have said gets rid of the problem? thanks please reply soon before i get a chance to drive it off the nearest cliff.

-Russ

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I went through a lot of the same steps. In the end I converted to speed density. My car drives great now and no expensive MAF.

Rich

 

what did you have to buy/do to convert to speed density?

 

You will need a 1227730 ECM and a 90 to 92 memcal (chip) for a LB9 (305 TPI). I got my ECM and a hypertech memcal from ebay. $60 and $40 respectivly. You will also need a new knock sensor and possibly a custom speed sensor. I can not comment to much on the speed sensor because I know there are differences between the camaro and birds as to what year they went to a electric spedo. I think yours is electric. Along your conversion you will run into a lot of people that will tell you to get a custom chip programed that disables the speed sensor error codes. I look at it this way, why disable something the engineers took so long to invent. Plus my car would stall every time I came to a red light before I got the custom speed sensor installed. Bottom line if you want proper idle stadigy make sure you have a speed sensor. Your current ECM wants a 2000 pulse per mile DC input and the new ECM will want a 4000 pulse per mile AC input. Here is a link to a person that got me motivated to do the swap. http://www.eecis.udel.edu/~davis/gm-eproms/. Let me know how I can help I think this is a worth while venture and I am glad I did it. My 87 L98 is next to get the swap since I got code 51 from it today.

 

You have obviously done a lot of work. Now you will have to troubleshoot. You will need a digital voltmeter to proceed. You will need to look at the schematic and verify that all voltages are going to the MAF sensor at the correct pins. Also you will need to verify that the burnoff is occuring. It will be easier and probably cheaper to repair what you have than convert to speed density. SD is the LESS desireable method of calculating air flow and density. The only reason Chevy changed was cost. The newer LS1 engines went back to MAF because it is more responsive and enables the ECM to better control fuel delivery. I will pull my notes and repost, I have had a lot of problems too. I'll try to give you the places to check to verify operation.

 

thanks for the info, i have the GM shop manual and ive probably done most of the diagnostics you are talking about but anything you have i would still like to see in case there is something i have missed. thanks again.


-Russ

 

Russ, I would check to see if the MAF inputs to the ECM are getting any signal. Easiest way to do it would be to start the engine and let it idle, then simply unplug the sensor connector or the power relay. In a normal TG the engine idle will drop, or in many cases it will stall. If that happens then at least you know there is some reference signal going to the ECM. I think you will find that the MAF is probably doing something. After that I would start looking for vacuum leaks or something you think might be unrelated. LOL

 

thanks danno, when i replaced my egr a few weeks ago i did find a vaccum line that was open and i plugged it since then it hasnt been idling rough or stalling on me like it was before but thats because my EGR was bad.

 

I had the same problem for many months in my 89 IROC. It drove me NUTS!! Finally I discovered that the problem was that the MAF sensor was not grounded well enough. I ended up cutting the two ground wires in the MAF harness and grounding them directly to the body. And presto -- no more code 33. It felt so good to drive my car without the check engine light on for the first time in six months! It ran a lot better and idled a lot smoother too; I didn't realize how badly it was performing until I finally fixed it.

I still don't know why there is inadequate ground in the wires. I inspected as much of the harness as I could and I tightened the %$#$ out of the two main cyliner head grounds. There is some ground there - enough to light a test light and register 12 volts on a meter - just not enough to satisfy the MAF sensor.

Hope this helps.

 

thanks, ive never heard of anyone fixing it by adding a ground, so ill give it a shot tomorrow morning. where did you get the idea that it was a bad ground? thanks

Russ

 

i found my problem, it turns out since the MAF was the first thing i replaced, and the relays were definately bad, they might have fried the new MAF, i replaced the MAF a second time after everything was changed and it works fine.