Greetings Ford guys & gals,

First-time-poster, long-time-"stalker" here, who is in desperate need of your help.

About me: Above-average backyard mechanic for 33 years, with formal training in heavy-truck diesel mechanics, who suffers horribly from OCD and strives for perfection at everything I touch.

About my truck: 1999 Expedition XLT, 4.6L Windsor with PI heads, 217k miles, owned/serviced for almost 4 years (bought it just under 170k miles). Had the traditional exhaust manifold gasket leaks (due to rotted studs @ back of engine) when I bought it, but never caused any issues until earlier this year--louder sound, and CEL for O2 sensor (bank 2, sensor 2).

So, I did my first head-job. Cleaned out the oil valleys, lapped the valves, replaced timing chains/tensioners/guides, cleaned all passages in TBI, all new gaskets/seals/head-bolts (everything torqued according to AllData specs), and new EGR tube. While the top-end was out, I carefully removed the wiring harness and cleaned it gently with diesel fuel and a nylon brush, before final cleaning with electrical contact cleaner & compressed air.

Got it mostly back together, without ever starting it, until 2-1/2 months later (had to take time off for personal). On "starting day", I disabled the ignition & fuel, and cranked until I had oil pressure. Enabled ignition & fuel, and found the first problem: no ground signal to the fuel pump relay.

So I jumped the relay, got 40psi fuel pressure, and proceeded to crank. As quickly as it fired, it died. I was able to keep it running with my foot on the accelerator, though I could hear & feel the misfire. After a few attempts, I got a code P1504, Idle Air Control Circuit Malfunction. I tested and replaced the IAC Valve/cleared code, with no improvement (new valve and old valve tested the same; 9.9 ohms between terminal and no shorts to body, but old valve was pretty carbonned-up).

PROBLEM #1=No ground signal from pcm to fuel pump relay. I promise you, it was not easy overcoming my OCD and fixing it the way that I did--but I want the truck running. So, I cut the ground wire and connected the relay-end to the chassis (pump runs whenever key is in "run" position). The other end (from pcm) is capped-off.

PROBLEM #2=I found that the injector to cylinder #1 is not injecting fuel. New plug came out dry, spark is great, 190psi compression. Noid light test failed, though I have 12+volts on the red wire, but the ground signal from pcm fluctuates at lower ohms (when running) than injector #2 (injector #2=no problems).

PROBLEM #3=I went for a test drive. Except for the low/slightly rough idle (sounds like I put performance cams in it!), it ran well with lots of power, but I got more codes; none of which had to do with the #1 cylinder not firing:

P1504 Idle air control circuit malfunction
P1507 Idle air control underspeed
P0156 O2 sensor, bank 2, sensor 2
P1152 Lack of heated O2, bank 2, sensor 1, indicates rich
P0171 Bank 1 system too lean
B1145 Right front speed sensor input circuit malfunction
Also, my A/C compressor won't engage (freon is in there; 100psi on low side without compressor engaged).

Now for my admission of stupidity, or stress (and you might have done this, too, if MY wife was over-YOUR-shoulder nagging YOU, while you were trying to pump out a full tank of fuel, because you didn't want it going stale)...
...I MAY HAVE--though I can't quite recall (too much nagging going on at the time)--applied power to the ground terminal for the fuel pump relay, about 4 months ago.

Could I have fried the pcm? Should I just pull the wiring harness, and check every wire?
I already checked the main connectors for bent pins; all were good.

New info: Just last night, I had to move my truck, and it wouldn't crank, unless my friend tapped on the ground wire at the battery terminal. I cleaned the wires & terminals thoroughly, charged the (8 month old) battery, and cranked it this morning. Still skipping, still low idle. Haven't done anymore 2day, as it's raining heavily here and inside bays are full (with $$-making jobs).

Sorry for the long post, I appreciate any help, and when it's working right, I'll definitely post what I found. Then, we can all celebrate over a beer or twelve!

 

The first thing that popped to mind is you pinched the harness between the engine and transmission or the large connectors by the starter solenoid are loose.

 

I agree sounds electrical, check all the grounds did you pull the motor? or just the heads, everything that you have a code for is on the passenger side. so thats were you need to keep looking, no power to o2 heater circuit, you need 12 volts there, your not getting it maybe a blown fuse or wire off the battery of to the underhood fuse box, work on your electrical, thats were the problem lies. follow your harness, stop putting parts in, something is unplugged or not grounded properly, If you pull your hair out bad enough pm me and I have a 99 and 2001 exped with the 4.6, I can look over them and see if something is weird that you might have missed. Get a light and follow that harness.

 

Try a different battery.

 

Yeah, I'm thinking harness as well. I did not pull the engine, just the intake and heads. I haven't checked the O2 sensor plug, or A/C plug, for power, as of yet. I did pull every fuse from both fuse panels and look at them, all good. I'd assume that I pinched the harness, except that I installed the harness after installing the heads (but before installing intake manifold). I installed a new Deep Cycle Marine battery in January of this year (out of necessity & availability), but I do have other (auto) batteries that I can try out.

Work is busy right now, so it might take me a couple days to get to my truck, but I will get back soon with further diagnosis, or, resolution. Thank you all for your input; any more ideas are certainly welcome.

My next beer is for you, and you, and you, and then for me. Cheers!