I've asked everywhere else, so I figure I'll throw one out to y'all too.

Got this one at work, 5.4/4R100 4x2 with 800K (yes, one eight, two zeros, one K indicating thousand) miles on it. It's a shuttle van that runs from Columbus to Atlanta. A Firestone store in town had it originally, diagnosed it and threw a mass air sensor on it. It had P1101 stored as a hard fault (MAF V out of self test range) on KOEO and KOER; it won't even go to the output state test during KOER. The MAF didn't help none. They re-ran their tests and figured the PCM was bad.

So, they tow it to us, I insist that we should go back over and compare notes before throwing a $300 PCM at it. "Noooooo, just program the PCM and install it." Alright. No change.

Idles okay, as soon as it's in gear, the engine stalls. Balancing brake and throttle can get it going down the road with a severe bog initially, then once it gets past 15-20 mph or so, it'll putter down the road decently enough.

BARO is stuck at about 139 Hz (should be 155-157ish around here), long term fuel trims are way negative, about -23% on both banks, MAF V at idle hovers around 0.15-0.20V. I have not verified fuel pressure as of yet. VPWR at the mass air sensor is good. MAF SIG and RTN from the mass air to the PCM are good. My brain isn't working properly with everything that's on my plate at work, so I'm askin' for any ideas from the masses. I haven't gotten the okay to go back into it and re-diagnose it yet. Thanks y'all.

 

I don't know what any of your BARO VPWR SIG RTN means but it sounds like a vacuum leak to me. An easy way to test all your vacuum equipment is to pinch off each hose with a pair of vice grip pliers. Just an idea dude.

 

I'm kinda ruling out a vacuum leak since the fuel trims are so far negative. I'd expect to see positive long term fuel trims if there was a vacuum leak (like the PCV elbow) since the PCM is trying to compensate for un-metered air entering the engine.

 

Yeah, well you do it for a living, so.... Just remember, vacuum leaks can be VERY tricky. It doesn't take much for it to really upset an engine. Even something as stupid as a worn out brake booster can cause enough of a vacuum leak to make the engine run bad at idle, but be so subtle that nobody can figure it out. (that's what was wrong with my girlfriends Ranger. 3 dealerships couldn't figure it out.)

 

What are your O2 readings? Is it black smoking @ idle? Checked the F/P regulator for fuel in vacuum line? With F/T that far out of fuel control, I would think you were getting some rich readings. Also check grounds.