I seem to constantly have problems with error codes over the last few years. I am now getting a 33 code on my 1989 model vette. Not long ago I replaced the MAF and TPI and had it set by a mechanic. Before that I replaced the MAF, MAF burn off relays, IAC, ECM, Coolant sensor. After replacing the MAF this time I am still getting a code 33. From the code list I have for an 89 model it say Mass Air Flow Sensor High. Does that mean the TPI needs to be reset? I just read somewhere it could be the ECM again.
I have has fast idle problems in the past. I haved cleaned the throttle body and replaced the IAC at that time.

When I am driving now the check engine light comes on and goes off.
The car stumbles and then picks back up after the light goes out. The problem seems to be getting worse. I have noticed the MPG has fallen also.
I have read where K&N air filters which require oiling can get on the MAF. Can this ruin them?
Could this increase in airflow cause a problem?


I am in a small town and the Chevy place here is more qualified to work on family cars.
Anyone got any suggestions other than get a Honda?

Thanks to all on this site for your answers and insight. I have been on some of the other car forums. They spend more time bashing each other than exchanging info. Maybe there's a reason for it.

 

Hi Revets00, I've revived an older Thread: relating to code34, has direct relationship with your problem .. code33 is ECM is reading high airflow value, code 34 is Low flow. I can totally relate to your code33, I had it since it began in 2001. LOL

 

I had the K&N oil fouling problem on my 86.

I just removed the MAF, turned it upside down (to prevent fluid from running into the electronics) and shot the wires with spray carb cleaner.

BLM and Intergrator values went back to normal.

Jake

 

Wow, could it really be that simple. It occurs to me my first code33 arrived with the new K&N filter, that was years ago. So the burnoff isn't able to clean it off. Although I still got the code with a new Granatelli maf., which doesn't utilize burnoff. I suppose it could affect that somehow. Sure worth checking out.

 

I would check the ECM again, replacements are all rebuilt and they can fail at any time, no matter how old. Symptoms you exhibit are exactly what I had, turned out to be the ECM.

 

For my part, I installed new/remf. ECM. .. new relays from GM. dealer, new maf's .. GM. guy ran new wires from maf to ECM. still got code33. Wouldn't it be unlikely a new ECM. would have the exact same fault? I'm almost ready to theorize that maybe the wiring's age may be affecting what the ECM is seeing, since it's working with such small voltage values. The new prom took care of it! for me .. I think I saw some new hairs in my head last night (Maybe just Buffalo Hair) ..

 

Brain food
http://members.shaw.ca/corvette86/Code%2033.pdf
http://members.shaw.ca/corvette86/intermittents.pdf

 

Thanks for the input. I went back to the dealership here and talked to a mechanic. He give me some good advice, sell the car.
He said from his experience they are all trouble and they don't like to work on them simply because of the reocurring problems just like I have.
He said a 33 could be the ECM. He said check the wires leading from the ECM plug by moving them while the car is running and see if it goes crazy. I am using an Advance Auto parts ECM along with the other stuff. Most people cannot afford to buy a GM MAF or ECM. Who knows they are probably made in Mexico or China also.
Thinking back I do seem to have more probelms since I put the K&N Filter in. Maybe it pays to leave well enough alone.
Maybe I just have a lemon and no one else has these continuing problems.
Hope everyone has a Merry Christmas!

 

Thanks, I printed that out. Good information.

 

Ask that mechanic/technician if he feels the same about women? I think maybe they don't like to work on vette's .. because they're not really qualified to work on them! I had an experience like that with our local dealer here in Santa Barbara when I first bought the car and had trouble with the antilock unit, they weren't qualified to work on it, they advised me to go elsewhere .. No Problem, and I've never been back & never will be. And I wouldn't buy a car from them if they were the last car dealer on earth!

Granted, the C4's are early and primative electronic/computer controlled vehicles by todays standards, by that reason alone they should actually be easier to diagnose and fix. As an example I have a BMW & a Mercedes, believe me, they have more intermittant gremlins than the C4's. My 8mo. old transmission computer on the Beamer went out again cause water somehow got into it, bad location .. An ECM. for a C4 is $100.00, try buying one for a BMW or MBZ. So far I've replaced 4 different computers in my Beamer. You should see what my friend goes through with his Porsche.

When put into proper perspective, our problems aren't unsolvable. Where else are you going to find a High Powered World Class Sports Car for so little money, parts readily available and cheap? So I say, it's like a relationship, you don't divorce her just because you can't figure out why she is unhappy. .. .

 

I just looked at my MAF after I read this. Mine is one of those rebuilt ones (Micro-Tech) is the name of the company. It has no wires in it as the one that come on it did. I have a photo but cannot post it. This one has some a type of metal that comes out spread arm in the tube.
I guess this is suppose to serve the same purpose. It'a a new sensor and still giving the error code 33 so I doubt this is the problem. I just checked the plug on the ECM and played with the wiring but didn't get any indication of a lose or broken wire there.

 

While we are on this subject I would like to ask another question. When you replace the ECM most auto parts require you take your Prom from your old ECM to go in the new one. Is this a good idea to use the old PROM? Do the errors come from the ECM or the PROM?

 

The PROM has programming specific for the engine it was designed to run with. New or rebuilt ECMs don't come with a PROM. That's because the ECM can be used in a variety of different cars/engines. Many 'F' bodies (Camaros and Trans Ams, etc.) use that same ECM as do our Vettes, but the PROM is programmed differently based on the engine specs.

You need to remove and reuse your existing PROM.

Most times, the errors are caused by a fault in the ECM or its wiring/connections.

Jake

 

My code33 came on exactly the same with the stock chip as with the hypertech chip, the new custom prom has the values set to 96 vs. 45gpm. stock value. It was a solution, the only one I found.

 

A lay explanation of the MAF workings is that airflow over the MAF wires cools them. This allows the ECM to be able to calculate the airflow and then send the correct signals to the injectors/ignition. If the wires are slightly coated with oil or anything else, the info the ECM receives will be incorrect, so it, the ECM, will send incorrect voltage signals to control fuel flow and ignition timing. Garbage in - Garbage out.

The burn-off function is SUPPOSED to clean off any contaminates to maintain the correct voltage changes; sometimes it can't though.

I don't know if oil residue is the cause of your problem but cleaning the MAF with a non residue spray cleaner can eliminate contamination as a possible cause. Besides it's easy and cheap.

Jake

 

What exactly was replaced? You list "TPI" but I suspect that's not correct.

Jake

 

I meant Throttle Position Sensor (TPS) instead of TPI. I have acronymitis. Yes, that has been replaced also.

Back to the ECM when I changed mine back in the summer I used my old PROM. That's why I asked if I should also replace the prom as well as the ECM.

 

I realize cars do have problems just some more than others. I guess I have been spoiled by having a Honda that is going on 300,000 miles.
It's only had the basic things you have to do such as waterpumps,timing belts,ect. The headlights have never failed to open. I have never had the digital dash go out. I have never had to replace the amps in all 4 BOSE speakers. I have never had to take the dash apart to replace a relay making the radio pop. I never have to worry about it overheating or installing a high volume water pump. I have never had to replace wheel bearings. I have never had to replace the antenna. I have have never had to replace the brake booster. Never had to replace the ECM,TPS,IAC,MAF,RELAYS,ECT.. I have never had to replace the tach filter. Never had to worry about vibrating mirrors, electric seats that don't work or a driver's seat that leans to the right (C-4). I never had to worry about a hood that falls on your head when the wind is blowing.
I think quality and dependable engineering has fell to the way side in American cars especially Corvettes. I don't mind working on cars from time to time but it is nice to have a car you can trust when your on a trip.

 

Carb Cleaner = bad idea. It does leave a residue. So does Throttle Body cleaner.

Brake Kleen/Brake Cleaner = good idea. No residue whatsoever. You've got the right idea turning it upside down though.

It's amazing, even with the burn-off feature MAF's on vettes seem to get real real dirty.

 

Maybe you're right, but the proof's in the puddin'.

My BLM/INTvalues were running 10 to 12 points rich before the cleaning, but afterwards returned to 128, give or take.

As I said before, Diacom verified those numbers, and since it's all about the numbers, I was a happy camper.

Electric contact cleaner is another option.

Jake