code 33

[d2thej]

I recently have gotten a code 33 on my 85 corvette, I have checked all connections, I have also changed out MAF with one I have with screen still in it and same code. I have not looked at the burn off module yet but I thought that was only to heat up the wire in the MAF to burn off any residuals left on the wires...My car starts right up and idles but coughs and sputters under light acceleration. Also Either my mileage is way down or my sensors are going crazy also....Any suggestions before I go to the shop.......:banghead:
Thanks in advance....

[fatherlarry]

Welcome aboard! Sorry to hear about your problem. Code 33 is telling you that the mass air flow sensor is high. What's the mileage on the car?

There are three codes that pertain to the MAF sensor: Codes 33, 34, and 36. Code 33 (mass air signal voltage high) is set when the computer sees a high mass air reading at low engine speeds. In other words, there appears to be more airflow through the MAF sensor than the engine can handle at a specific throttle and rpm.

The design of the MAF sensor is basic. A wire heats up when the car is running. The air entering the engine through the MAF sensor cools the wire. The more air ingested by the engine, the more air must flow through the sensor. More air means a cooler wire. The computer knows how much air is entering the engine by the temperature of the wire inside the MAF sensor. The air/fuel mixture is dependent upon having accurate readings from the MAF sensor. If there were a problem, a Code 33 or 34 would be set. Once a Code 33 or 34 appears, the MAF sensor will shut down and the car will go into basic strategy mode, coughing and sputtering, until the key is turned off for about 20-25 seconds. You'll know the MAF has stopped working when, "You let off the gas and it drops hard.

Here are a few reasons for a code 33. If the dark green wire (circuit 998) has an open circuit or a bad sensor; if the black, burn-off control circuit wire (circuit 900) has power with the car running; or if the system has a bad ground. Check for an open circuit on 998 at the ECM on connector B12. There are a few places to check for a grounding problem.The grounds on the '85 and '86 are on the rear of the driver-side head. Pull the wiper motor to check. Did the car ever show a code 34 as well?

Also check the throttle body, by simply depressing the cruise-control bellows and observing if the throttle-body linkage moves laterally instead of only rotating on the shaft. If there is noticeable movement, your throttle body is worn and the engine is getting unregistered air through the gaps.

It also could be the module, however, this rarely goes bad.

You might also want to check the oil-pressure switch If the engine feels as if it has an intermittent puttering with a fuel pump and MAF code set, the oil-pressure sensor would be the place to start. If the switch is bad, the engine tries to start because power to the pump at startup is fed through the ECM's fuel-pump-relay drive.

Also, to get a Code 33, circuits 998 or 450 could have an open circuit. You may have to run new wires for both circuits.

Hope this helps.