Ford 4.6 endless MAF issues

[Rochev]

2008 f-150 with the 4.6. it's my plow truck and ran perfect until this past spring when I ran it to remove the plow. MAF sensor code came on. I unplugged it and it ran fine. It sat again for a while until I looked into it. Next time, it ran poorly again and when I unplugged it again it would now stall.

Replaced the MAF sensor-no dice. Checked for leaks and wiring issues.

Bought an OEM motorcraft MAF since the data was still showing low voltage for it, and had only 3.6g at warm idle.

Found that the MAF plug terminals were all bent. Spliced a new one and restarted. Ran ok but still had a slight shake. Cold idle about 900rpm was 0.52g of flow. Too high. As it warmed up it got worse, as it's been doing, and was at 0.68g warm idle. If I floor it, it skips badly and doesn't move quick. Won't go up a hill without me downshifting it, though goes up my steep dirt hill in 4x4 low just fine. Goes around the yard fine, but it's not going to plow well. It's been almost triple digits and sunny and it's my only vehicle with working AC. It's a rusted heap but I wanted to use it for the AC.

Theres no codes and nothing pending. Engine and cab still visibly shaking at idle.

I don't know what else to do with it.

 

[dogememe]

Surprised you got a Ford to run without MAF. I've always had good luck getting GMs to run great with MAF unplugged but Fords never. Both my Escape and Crown Vic were undriveable with bad MAFs or unplugged MAFs.

If you have three sensors and a good connector/harness and it doens't work with any of them you must have some other issue?

 

[Rochev]

Definitely another issue but I had tunnel vision on the voltage issues with the MAF. Plus it's the only code that comes back.

It might be the cat because the exhaust is over 100° hotter before it than after it. I got 266 right before it, 160 on it, and post cat was 130. Although the exhaust is cut off under the bed so I'm not sure if that would make much difference

 

[Kira]

Overall condition? Is it an old gummed up, neglected mess?
Air intake OK? Gotta say it...injector cleaner...maybe.

 

[JavierH19]

Sounds like a ground issue which is what i had on my f150 when a rat chewed the wires when I had it in storage for months without driving.

Got this from a page.

Ford 4.6L engines feature specific ground connections for the Mass Air Flow (MAF) sensor, typically involving two distinct ground circuits in addition to power and signal lines.

For standard 4-wire MAF sensors found on most 4.6L applications (such as 1997–1999 models), the grounding is handled by:

PCM Ground: A Tan/Light Blue wire (Pin 2) that provides a low-reference ground signal directly from the Powertrain Control Module (PCM).

Chassis Ground: A Black/White wire (Pin 3) that connects to the vehicle's chassis or engine block ground strap.

In some configurations, such as the 2005 Ford F-150 4.6L, the MAF connector may have six wires, integrating the Intake Air Temperature (IAT) sensor, which also requires a signal and ground connection within that same harness. If the PCM ground wire is faulty, it can cause issues not just for the MAF but for other sensors sharing that reference, potentially leading to rough idling or performance codes like P0102 (MAF Circuit Low Input)

 

[D60]

Misfire counts?

I have an '07 4.6 F150, so curious what you find

 

[clinebarger]

You mean 5.2 grams per second? At 900 RPM that's about spot on.

If you fixed the MAF circuit & performance DTC's, Move on! My next step would be looking at fuel trims & balance tests to get a good idea if misfires are present.