Questions and Answers

Lumina MAF Sensor? Q. I have a 1990 Chevy Lumina car with a 3.1 liter. My problem is when my car idles for 40 to fifty minutes it starts to idle rough and tries to stall, it takes a couple of minutes of reving the engine to get it to run right. It runs great as long as I am driving and not idling long.

Also my car starts fine when cold but when well warmed up (about 30 minutes of driving) the same problem as above at startup and then runs fine after it clears. Someone suggested the MAF sensor but I can't find where it is located.

Thanks for any suggestions,
Jordy

A. That engine doesn't use a Mass Air Flow (MAF) sensor. It uses a Manifold Absolute Pressure (MAP) sensor. The computer sends a 5.0 volt reference signal to the MAP sensor. As pressure changes in the intake manifold occur, the electrical resistance of the MAP sensor also changes. By monitoring the sensor output voltage, the computer can determine the manifold absolute pressure. The higher the MAP voltage output the lower the engine vacuum, which requires more fuel. The lower the MAP voltage output the higher the engine vacuum, which requires less fuel. Under certain conditions, the MAP sensor is also used to measure barometric pressure. This allows the computer to automatically adjust for different altitudes. The computer uses the MAP sensor to control fuel delivery and ignition timing.

The MAP sensor is located between the engine and firewall on top of the engine towards the right side. It is a square box with a single vacuum line and a three pin connector. This could be the cause of the problem you are experiencing.

Additional Information provided courtesy of ALLDATA