Mass Air Flow Sensor - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

100Grand · 02-01-2006, 12:11

Hi, I'm new here but have been on other boards for years. I already did a search and couldn't find an answer.

I have a new to me 90 Grand Marquis with a 5.0. The car has sat for a while and lurches and hesitates often. The RPM's are constantly up and down even when warmed up. I got the car free and don't want to/can't sink alot of money into her. The above to me sounds like the MAF. I, for the life of me cannot find it on this car. I googled for pics and can't seem to find a 1990. But my parts stores all have one in stock. I don't want to waste the gas to see what it looks like there (plus I don't have the $ til this weekend). My question is, where on my car is this sensor, if I have one. I don't have anything coming off the intake hose that resembles the ones I've seen but there is a harness and clip attached to a housing near the intake manifold. I undid the clip and the car seemed to idle better from doing that. Could that be it? Please help!

Great board by the way! I've lurked here before, had a '92 Sable before this one.

amo4387622 · 02-01-2006, 19:41

You do not have a MAF sensor. For your problem I would change the fuel filter if not done. Also I would check the voltage of the tps sensor with ignition on but engine not running the throttle plates closed voltage should read .50-1.0 volts. Then at full throttle voltage should read 4.0 volts. I would also do a full tune up plugs, wires, and cap and rotor if need be. Also think about replacing the pcv valve. Also clean the Egr valve too.

ryoder · 02-01-2006, 20:55

I'll agree with the tune up and checking the throttle position sensor,that should solve your problem,plus change your air filter

100Grand · 02-02-2006, 14:47

You sure I don't have one? I asked AllExperts.com and they said I do have one and it's on the firewall.

amo4387622 · 02-02-2006, 19:13

You do not have a MAF sensor because you have a speedensity computer which does not use a MAF sensor. The only thing I can thing of that AllExperts.com is telling you that would be on the firewall is the MAP sensor. And the only place you can mount a MAF sensor is on the Air Intake before the throttle body, Because what the MAF sensor does is tell the computer how much air is going into the engine so the computer can through just the right amount of fuel to mix with the air so you get that right amount of mixture which is 14.7:1 (14.7 parts of air to 1 part of fuel).

dcspo5073 · 02-02-2006, 20:28

I had that problem with a Ford P/U, and it was an O2 sensor that was throwing the RPMs off. It would jump about 500 RPMs up and down while at idle.

foxbody5l · 02-04-2006, 05:11

Have you checked for vacuum leaks yet???

02-04-2006, 05:58

Along the air hose near the intake manifold, there is a connector of some sort. It does not look like a MAF that I have ever seen before but if I unplug the plug going into it, the idle settles down. Not drivable because it's stalls at that point, but drops down and stays running if I give a slight amount of throttle. Any idea what that is? I really need a CHEAP fix right now. I can probably live with the high idle for another week (next payday) but if there is something that can be done for free I'm all for that!!
I did briefly check for vacuum leaks and did find one.

100Grand · 02-04-2006, 06:00

Along the air hose near the intake manifold, there is a connector of some sort. It does not look like a MAF that I have ever seen before but if I unplug the plug going into it, the idle settles down. Not drivable because it's stalls at that point, but drops down and stays running if I give a slight amount of throttle. Any idea what that is? I really need a CHEAP fix right now. I can probably live with the high idle for another week (next payday) but if there is something that can be done for free I'm all for that!!
I did briefly check for vacuum leaks and did find one.

foxbody5l · 02-04-2006, 08:19

that is your Manifold Absolute Pressure (MAP) Sensor. Since you unplugged it the PCM found a hard fault and goes into limp mode. That is why the Idle calmed down and why it won't really drive that well. You really need to run some self tests to find out what is going on with the car. You don't have an Air Meter (MAF) so that isn't the problem. It could be anything from a bad Throttle Position Sensor(TPS) to a Lazy O2 Sensor. I would see if there is an Auto Zone in your area that would at least get a code for you so you have some sort of direction. You will spend way more time and money by Shotgunning parts at it.