Should my car die if the MAF is unplugged?
- Thread starter 95Vert
- Start date
94-302-vert
Active Member
I want to say yes it should.
I had the tube between my MAF and intake undone once and had to rev the car to keep it running...
I had the tube between my MAF and intake undone once and had to rev the car to keep it running...
OrangeMustangGt
Founding Member
legalize420
Active Member
95WhiteVenom
Founding Member
I have done it three times when switching back and forth at the track from my stocker to my Pro-m 80mm.
The car will,...
A. Run fine for 5-10minutes then get real sluggish and then die (check engine light comes on before the car starts going nuts).
B. It will crank an immediately the check engine light will come on and it will die shortly there after.
These are my experiences your may vary a lil bot no matter what YES IT WILL DIE WHEN UNPLUGGED!
The car will,...
A. Run fine for 5-10minutes then get real sluggish and then die (check engine light comes on before the car starts going nuts).
B. It will crank an immediately the check engine light will come on and it will die shortly there after.
These are my experiences your may vary a lil bot no matter what YES IT WILL DIE WHEN UNPLUGGED!
It shouldn't die. I drove mine around for like 2 weeks without the MAF plugged in, because the stock one had gone bad unexpectedly, and I hadn't gotten paid yet... It just runs in speed density for the most part, since it just relies on pre-programmed fuel tables in the computer.
MLC Stang
Founding Member
I see there is some disagreement in this thread.
Allow me to quote Charles O. Probst, a Ford automotive engineer and author of “Ford Fuel Injection and Electronic Engine Control Systems” one of the best books out there on this subject.
SHORT ANSWER: Your car SHOULD run with the MAF disconnected.
LONG ANSWER: If the PCM detects ANY sensor input that is out of range (including the MAF) it is designed to go into Failure Mode Effects Management (FMEM). In FMEM the PCM compensates for sensor inputs that are out of range by substituting an average value for the particular sensor from ROM. For example, if your Engine Coolant Temperature (ECT) sensor is reading out of range, the PCM will instead use an average figure for that temperature so that the car can continue to run until you replace the sensor. It will also turn on the check engine light to indicate a sensor is bad.
The case of a disconnected, or just bad, MAF is a little bit different but not much. The MAF provides a very accurate indication of engine load to the PCM. If its input is out of range or not present, the PCM needs a substitute indication of load in order to keep running. Since load is greatly variable, an average cannot be used. So, in this case, the PCM uses the input from the Throttle Position Sensor (TPS) modified by the ECT and ACT signals to calculate a substitute value for load on a real-time basis.
So, YES, the EEC-IV engine control system in our cars is DESIGNED to allow the engine to continue to run with a bad sensor, including the MAF.
If your particular car does not, then it is due to some additional problems not just a bad or disconnected MAF. (e.g. if your MAF and TPS are both bad… you are NOT going to run.)
PS) This is also why it is very important to clear the Keep Alive Memory (KAM) by disconnecting your battery for 5 minutes after replacing a defective sensor or other component that causes a check engine light. Once the PCM goes into FMEM and substitutes an average value for the bad sensor/part, just replacing it with the new part won’t fix the problem! After you replace the component, you must also clear the KAM to get the PCM to stop using the substitute value for the bad part. If you don’t clear the KAM, the PCM will continue to use the substitute value even after the new part is installed! Disconnecting the battery for 5 minutes allows the memory to decay, which removes any stored substitute values that were being used.
Hope that helps.
Allow me to quote Charles O. Probst, a Ford automotive engineer and author of “Ford Fuel Injection and Electronic Engine Control Systems” one of the best books out there on this subject.
SHORT ANSWER: Your car SHOULD run with the MAF disconnected.
LONG ANSWER: If the PCM detects ANY sensor input that is out of range (including the MAF) it is designed to go into Failure Mode Effects Management (FMEM). In FMEM the PCM compensates for sensor inputs that are out of range by substituting an average value for the particular sensor from ROM. For example, if your Engine Coolant Temperature (ECT) sensor is reading out of range, the PCM will instead use an average figure for that temperature so that the car can continue to run until you replace the sensor. It will also turn on the check engine light to indicate a sensor is bad.
The case of a disconnected, or just bad, MAF is a little bit different but not much. The MAF provides a very accurate indication of engine load to the PCM. If its input is out of range or not present, the PCM needs a substitute indication of load in order to keep running. Since load is greatly variable, an average cannot be used. So, in this case, the PCM uses the input from the Throttle Position Sensor (TPS) modified by the ECT and ACT signals to calculate a substitute value for load on a real-time basis.
So, YES, the EEC-IV engine control system in our cars is DESIGNED to allow the engine to continue to run with a bad sensor, including the MAF.
If your particular car does not, then it is due to some additional problems not just a bad or disconnected MAF. (e.g. if your MAF and TPS are both bad… you are NOT going to run.)
PS) This is also why it is very important to clear the Keep Alive Memory (KAM) by disconnecting your battery for 5 minutes after replacing a defective sensor or other component that causes a check engine light. Once the PCM goes into FMEM and substitutes an average value for the bad sensor/part, just replacing it with the new part won’t fix the problem! After you replace the component, you must also clear the KAM to get the PCM to stop using the substitute value for the bad part. If you don’t clear the KAM, the PCM will continue to use the substitute value even after the new part is installed! Disconnecting the battery for 5 minutes allows the memory to decay, which removes any stored substitute values that were being used.
Hope that helps.
DougNuts
Founding Member
My car ran without it plugged in. I drove it probably 20 miles that way, it just didn't run well.
Thanks guys, especially MLC for that explanation. I just wanted to see. They had me worried already. PHEW, one less problem to worry about.
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