Code 66 - Engine runs like crap. Need to verify bad MAF sensor

[MustangLX-5.0]

Update - Video added in post #7
So I just suddenly got a code 66 2 nights ago. Before this, I had it running great. Now, it hesitates bad and wont stay running and is smelling bad of rich fuel mixture. The humidy in the air that night was near 95% and it was very damp out. I wonder if this had anything to do with it, as the previous whole week it wasn't no where near as damp out. But, it still runs like crap... so I followed JR's testing procedures and these are the results I got.

Pins A & B KOEO - 12.4V
Pins C & D + Pins B & D Key off - 68K Ohms and it slowly climbs
Engine running and warmed up. MAF connected and pins C & D backprobed. Voltage varies from .9V - 1.2V. It will climb to over 2V when I rev up the RPM's.

Is this just a bad MAF sensor, or do I have another problem? Is there a resistance check I can perform directly on the MAF while it is unplugged to verify this?

 

[liljoe07]

Monitor the signal voltage at idle from PIN D to ground or PIN B. Then monitor the voltage at PIN 50 of the ECM to a ground. Those two voltages should be the same. fi nots its a wiring problem



Or just swap in a spare MAF sensor if you have one. Then re-run the codes.

I dont know of a Ohm test you can do directly to the MAF sensor.

 

[MustangLX-5.0]

Idk, I pulled the panel off but I still cant get to it. I cant tell what is what because there are at least 50 wires in there. Do I have to remove the dashboard to get to the PCM?

On some other notes. The engine surges like crazy. It goes rapidly up and down no matter how far I push the gas. It keeps stalling out. I disconnected the MAF sensor and it seemed to run a little better. But it still is blowing out craploads of black smoke.

Yesterday, I connected a scanner to it. The first time I read codes with the key on / engine off, I got a code 66, and that was it. I started the engine and shortly after, scanned for codes while it was running. First I got a code 11, then came code 21, then code 41, then 91. After it was running for awhile, I shut it off. I sprayed MAF cleaner into the sensor and let it dry out. Started the eninge back up and then scanned for codes again. This time I got codes 44 and 94. NO code 21, 41 or 91. But it still runs bad. It seems like it has gotten worse since yesterday. I can barely keep it running. It seems like it was just 3 days ago and it was running flawlessly. It did seem to lack power and have a slight delay in the throttle but it still ran fine.

Checked fuel pressure and its sitting at 32-34 psi at idle. Rev it up and it goes to 38 - 40 psi. Pull the FPR vac line and it goes to 41 PSI. While the scanner was still connected, I promted a balance test. I got a code 9. So that's fine.I fixed ALL vac leaks, replaced the ECT sensor ... now what? Is the PCM taking a dump or something? I have no idea why it would suddenly jump up and run horrid like this. I was driving it for a few days even.

I cleaned off every ground terminal I could possibly find. That meant removing the screw and using a wire brush tool on my dremel and making the screw and terminal shiny again. So no bad grounds.

I got a nasty hole in the passenger side mid pipe near the muffler. It's right on the seam. I patched it a week or two ago, now it seems it has either re+opened or become worse. I dont know if that would have anything to do with the thermactor codes. The air pump appears to be doing its job. When I unplug the vac lines to the termactor control valves, the exhaust gets a LOT quieter, but it doesn't seem to make the engine run any better.

Was up at the parts store today and had planned on getting another MAF sensor. They had 3 different sensors for my year 5.0. And apparently all they sell now are the entire MAF sensor + MAF tube. They don't have just the sensor... Dumb. Since when did they change that... and add a core charge?

 

[MustangLX-5.0]

I'm going to record a video of how its running and upload it in a bit.

 

[Kdubslugga]

dealing withe the same issue bud!! If you try and bring the rpms up and hold it at like 2 grand does the car cut out?? If you unplug the meter is there no change at all? i got a ne DBX meter and my car ran likes yours, i sent the meter back and it was indeed bad...

 

[Kdubslugga]

if u find out its the sensor, pm me i have several good ones at the house, im betting its bad

 

[MustangLX-5.0]

Here's a video I just took. It's from my Touch Pro 2 phone and is all I can really get at the moment. It was raining all day today. The sound isn't bad tho.. make sure you watch the whole video because I unplug the MAF at the end.

YouTube - 92 Mustang 5.0 running bad, stalling and surging

 

[Kdubslugga]

sounds like you have a .650 lift cam lol.

 

[MustangLX-5.0]

I know the fuel gauge is low. I don't think it's bad gas cause I cleared all that crap out. The gas in the tank is from the recent fill-up after I finally got it up and running. I HAD a little over and 8th of a tank when this problem first popped up a few days ago. Now it's just guzzling up that gas like a thirsty person in the arizona desert.

Once after I kept it running while it warmed up, I unplugged the TPS. Unusually, it seemed to run a lot better. Keep in mind, the engine was warmed up.... Throttle response improved to near instant results with it unplugged. Idk if it is a bad TPS or just that it was already running super rich and unplugging it just gave it the ait (and not the fuel) that it needed. I never got a code for the TPS. I'm going to test it today. Doubt it's bad.. but just in case.

 

[MustangLX-5.0]

Anyone? I'm stumped on this one and its totally un-driveable.

 

[MustangLX-5.0]

Well, now it wont even start. I pulled all the plugs and cleaned them.. tried again and it still wont start. I pulled the Dis and cleaned all the contacts off. Can't think of what is wrong. It tries to start put stalls right out. I have to hold the gas halfway in to even get it to turn over. Tried unplugging the MAF ... then replugged and did the same for the TPS.. nothing. Car is now dead.