Unplug MAF sensor, Car still runs!

Car will run in "limp" mode when the MAF is unplugged or damaged.

It's running off the failed MAF table - and sometimes they are pretty close...

Might need a new MAF all together. Take it apart and check the 2 elements in it to make sure they didnt burn out.

miller92063,

The Powertrain Control Module (PCM), or main computer in our cars has what is called a Failure Management Effects Mode (FMEM).

The PCM relies on readings from several sensors to provide it with information regarding operating parameters of the engine. If the PCM detects any sensor input that is out of range (like the MAF, ECT sensor, ACT sensor, O2s, etc.) it is designed to go into FMEM so the car can continue to run.

In the mean time, it throws a trouble code and turns on the check engine light so you know that something is up.

In FMEM the PCM compensates for sensor inputs that are out of range. For some sensors it does this by substituting an average value for the particular sensor that is stored in ROM in the PCM. For the MAF, however, it uses a combination of real-time readings from the throttle position sensor (TPS) and the engine RPM to operate the engine.

And, if you've got a bad MAF to start with, your engine just might run better using those substituted values.

PS) This information is from the book "Ford Fuel Injection and Electronic Engine Control", by Ford Engineer Charles Probst.

yeh mine did that.. was a bad maf... unplugged it.. and it actually ran better... got power back..
replaced it and has run fine ever since.