So my CEL popped up. Car did NOT want/like starting... Would not idle on its on, id have to feather the gas to keep it going about 5-10 seconds, then it would straighten out but would pop and cough almost... Not a misfire, it is just waaaaay fat and rich. So I get the codes scanned, just 1 code which is a P0100. To put it short, my car is running like ****, I'm assuming it's running on speed density now. The PCM was tuned by Solomon and was running 110% until this code happened. So, I took the MAF off, didn't look dirty but cleaned the MAF with some LPS, cleaned the air filter, and wiped the inside of my 1LE TB elbow, as well as my lingenfelter CAI pipe with a rag with some rubbing alcohol. None of which was really "dirty" there was some slight dust build up but isn't surprising considering im running a K&N/Lingenfelter combo which is probably pulling some serious air. Anyways... What can I do to fix this? I can't afford to keep driving the car this way, it's running so rich my MPG is down to 8-12. I'm also afraid it's running so rich I risk diluting the oil around the rings and kill the motor. My MAF pigtail looks fine, nothing unusual, no melted wires or the like. What color wire should have 12V with the key in the on position? My guess would be pink because the black is the ground obviously... I'm guessing the yellowish white one is where it gets its signal from? Any advice? I really want to get this fixed, every time I down shift now it pops, snaps and crackles like some old truck without a muffler

 

Additional information on the car; 97 Z28. Lingenfelter CAI, K&N filter, Holley Airfoil, stock manifolds, gutted cats, modified stock Y going into a flowmaster merge, into Magnaflow catback, MSD 6AL, Solomon Tune with !EGR,!AIR,!CPS,and! Rear 02's everything that has been tuned out is still on like the air pump, and EGR pipes (I have to pass visual inspection in NC) I have read of some having problems with the EGR/AIR stuff still being installed while tuned out.. I haven't had any problems with this car until now... I've had the car and tune for going on 25k miles now.

 

Pink is 12 volt keyed hot. Yellow should be the signal wire. Black is ground. It is either the wiring, the sensor, or PCM. What are the MAF readings at idle? If you have a scanner this should be pretty easy to diagnose.

 

Okay that's what I had thought. I'm going to go test the wiring now with my multi meter. I do not have a scanner anymore.

 

Conditions for setting a P0100--Engine running greater than 50 rpms, ignition voltage greater than 10 volts, MAF frequency varies less than a predetermined minimum amount, all the above met for 1 second.

Try to get the freeze frame data for when the code is set to see exactly when it is occurring.

Idle MAF gm/sec should be ~3.9gm/sec.

MAF signal voltage should be 5 volts with key on and engine off measuring between the yellow wire and ground (unplug connector). 12 volts between the pink wire and ground. Make sure you measure the plug ground as well as connecting the volt meter to the battery ground to ensure it is not a faulty ground wire. You can also do a continuity test on the ground in the harness to battery ground to make sure it is ok.
If the above tests are not reading, measure the voltage by probing the wires behind the connector to isolate the connector or the wiring. If still no voltage readings, try to measure the pcm connector wiring. If still no voltage readings, it is most likely the pcm.

If the voltage checks out good at the connector, it is likely your MAF sensor.

I hope this helps.

 

Okay, so multimeter read fine... But I didn't give up on thinking it was the MAF itself. So I started looking for MAF related fuses... the under hood fuse/relay box has a 20A fuse labeled "ENG SENSOR" pulled it out, it looked blown, but to double check used the multimeter to check and it was indeed, blown. Replace fuse. Go to the in car fuse box, pull out the "PCM/BATT" fuse for about two minutes to let the code clear, fire it back up and I noticed immediately the car fired up perfectly with no hesitation or that awful stumbling idle. And also the CEL did NOT! Come back on! I had tried 3-4 times just taking the "PCM/BATT" fuse out and hoping the codes would clear and not come back but every time as soon as I'd hit the starter it would act like the problem ever left indicating that it wasn't just a coincidence. Anyways, I took a test drive and got some groceries, sat in heavy traffic and hit the highway, CEL is still off. So my only Question now is what happened? What caused that fuse to blow randomly, and is "ENG SENSOR" just sly code for MAF?

 

Fuses wear out like any other item. However, if it blows again, you might have a problem. If not, I wouldn't worry about it.

ENG SENSOR (fuse 10) also powers all the O2 sensor heaters (only used for cold startup, they don't affect how it runs). It also powers either the TCC switch in A4 cars, or reverse lockout and CAGS solenoids on M6 cars.

 

I had also had a problem with the reverse lockout solenoid a few days ago. I just made a thread a few days ago about it, it is also back to normal. I'm glad it's back to normal, I was pretty pissed. Lol, I got a handful of 20A fuses in the center console now in case it happens again. It was a old as hell fuse so I'm sure it could've just been it's time. Just to be on the safe side I took some header wrap and wrapped the MAF wiring to prevent melting or grounding out.