well some background, 88 a4 stock 123K. It's been running fine for the first year but now I have a code 33 (MAF Signal Hi). I found original relays, so I replaced those sure that it would fix it. Nope. Starts up, idles high(~1000 rpm) then when you take off it surges, sometimes stalls. after the light comes on, I guess it goes into a failsafe, because it starts running OK but not well, I can smell the exhaust a lot. It only seems to do this from a hot restart. Sometimes on a hot restart it just dies right away. TPS and IAC are set up right. I've went through the GM chart for code 33, and the chart is leading me to a bad MAF, which is $$$$$$$$$.

Is there something I'm missing, or do I have to bite the bullet and buy one? Also, any experience with NAPA sensors?

 

I've replaced my sensors (87) with NAPA and no problems. Since they are the same sensor, you can undo one and switch out to see if one is a problem. If they are ok, you can always get an MAF from junkyd, camaro 3rd gen uses the same one, alot cheaper....

 

The relays would still be required if you had changed the MAF in the first place, so dont feel too bad. I would only use OEM for this part, nothing aftermarket, so stick with the original brand and try to find it wherever you can for the least.

 

I HAVE AN 88 CONVERTIBLE. I JUST RECENTLY HAD A CODE 33 AND 34. i GOT AN ESTIMATE INSTALLED FROM THE SHO FOR $700.00. i WENT TO MURRYS DISCOUNT AUTO PARTS AND GOT A NEW ONE FOR $239.00 MINUS $90.00 DOLLARS FOR YOUR OLD SENSOR CORE CHARGE. i HAD IT FIXED IN 10 MINUTES. THE REPLACEMENT FROM MURRYS WAS ALSO A BOSCH.

 

I'm still running the stock MAF from my old '86 IROC in the '88 Vette...

 

Sounds like you will need a used/new MAF! Sorry...

 

There are a few things that can cause a code 33 which is a high MAF signal. These could include a) an open wire or terminal at or to the MAF; b) faulty relays; c) faulty MAF sensor and the last possibility being; d) the ECM.

FAULTY RELAYS - There are two different relays used, one for power and the other for burn off, and if they are switched I have seen them give code 33, don't know why but I have seen this even though they seem to be the same relay with the exception that one comes with a shock absorbing strap and the other one does not. So just swap relays and see if that helps. Relays could be a good possibility and would be worth checking and you also need to try swapping them to make sure they are not the problem.

PROME REVISION - I want to point out that Chevrolet has come out with a revised PROM for the 1986-89 Corvette due to code 33 problems. Now before you go off and order the revised PROM you should thoroughly check out the other possible problem sources. This is not a hard code to fix but you may have to do a little looking.

WIRING - Wiring is not a common code 33 problem but if you have an intermittent problem that could be a sign of a poor connection of one of the terminals at the MAF sensor. If the light comes on right away that could also be a sign of a broken wire. If one of the MAF sensor wires becomes open it will set a code 33 but, this condition would happen all the time probable shortly after start up. If you have access to a scan tool I would hook it up and read the airflow; when warm it should be around 6.0 grams per second. Then try wiggling the wires and if it shoots up you having a wiring problem. If it's high all the time then you could have an opening in the wiring. I would check the MAF thoroughly as the first source of the problem.

ECM Upgrade - I suspect that you have a #1227165 ECM in the car and that could be the problem. This is the original style ECM used in the 86 to 89 Corvettes. Chevrolet has had a real problem with the internal circuit board cracking on these original units and when this happens there can be all kinds of problems including code 33, 36, 34, 15, 51 and a few more. Drop down the ECM and see what the service number of the unit is and if it's a #1227165 replace it, if it's an aftermarket rebuilt and painted black, replace it as these old style ECM and most aftermarket replacement ECM units are of the old style. The GM number you need is #16198259. This is the GM replacement for the original #1227165 and is much better.

 

Do yourself a favor before spending $$$$$, double check the connection at the MAF, make sure it's clean and has a good connection.

 

 

Unplug the connection to the MAF and start your engine , if it starts and runs noticable better It is the MAF. I just went through the exact same problem, my problem started when I switched over to the K&N air filter, If you did the same thing take off the MAF sensor and buy some electronic cleaner that will not attack plastic and spray the inside of MAF You may get lucky. Time to CRUISE- my vette was down for 6 months with this problem.