Code 33 but MAF ok

[Bandit1200]

I'm having a somewhat intermittent issue with my 1989 Corvette where the engine cuts back to idle when the car is in gear and the throttle is pressed to approximately 20%. If held there the SES light will come on after about 5-6 seconds and a code 33 (high voltage MAF) will be stored. The problem is worse on the highway and it will often "cut back" when the throttle is just off idle. If I let off the throttle the engine comes back to life again and will run normally. If I push the throttle from idle past the 30% mark (approximately) then the car accellerates fine and runs very well. If the engine "cuts back" and I push the throttle further the car will spit and sputter and will run very poorly with no performance until I lift my foot and then the car will come back to normal.

It's as if the computer is reading the high voltage at the MAF below 25% throttle and below 2200 RPMs like it should, however changing out the MAF isn't working. Changing out the the MAF supply and burn off relays made no difference either. I've checked all the wires from the MAF to the ECM for continuity and shook them around during the test and no problems there. I've also switched out the TPS and it made no difference.

Has anyone had this issue before? Any ideas?

Thanks,
Andrew

 

[Schrade]

Sounds like good testing so far...

My FSM is LT1; diags procedure is not identical to L98... Do you have FSM?

 

[Bandit1200]

I do have the factory service manual, however when it comes to an intermittent problem it's not very helpful.

I've ordered the cable to connect the diagnostic connector to my laptop so hopefully when that arrives I'll see what the computer is seeing when it cuts back on me. The problem is there constantly until I've been driving for 40 minutes or so, although I can't contribute it to engine temperature because it can be hot and still have the problem, or cooler and not have the problem, it just has to be driven for 40-45 minutes before the problem goes away (usually).

 

[gmjunkie]

I do have the factory service manual, however when it comes to an intermittent problem it's not very helpful.

I've ordered the cable to connect the diagnostic connector to my laptop so hopefully when that arrives I'll see what the computer is seeing when it cuts back on me. The problem is there constantly until I've been driving for 40 minutes or so, although I can't contribute it to engine temperature because it can be hot and still have the problem, or cooler and not have the problem, it just has to be driven for 40-45 minutes before the problem goes away (usually).

Are the Digital Temperature Gauge and Analog Temperature Gauge in sink with each other from Cold Start to Operating Temperature??:confused At what temp is the vehicle going into Closed Loop from Stone Cold Start?:confused

 

[jazfe]

Code 33

I was having the same trouble with my 86. Changed the relays, pulled all of the wiring off the engine to inspect the connectors, cleaned all the connectors, changed the MAF, TPS too. Long story short, the TPS was bad. That was two I bought from Autozone, First one fell apart on the engine after three days and the second kept giving me the Code 33............Gave up and purchased a TPS from Chevrolet...............Problem solved

 

[jazfe]

Same trouble

I replied to your earlier thread.........My original trouble was hesitation. I checked the TPS and found it jumping so I changed that and all was well for three days until the TPS fell apart...literally. I put on another Autozone TPS and it worked for a few days and then started in with the code 33. The book led me to change the MAF and that worked for a day. I drove it for a few weeks to see if the car would work itself out but it never did so I purchased another TPS but from chevrolet this time since I had no faith in the ones from Autozone. I've been two weeks now on this TPS and not one bit of trouble.

 

[Toms007]

I'm going to merge these threads.