Got a 2000 F-150 with a 4.2 V-6, with 117,000 miles.

Was running fine then started to stuble when you first got into the throttle, particularly in lugging situations. This progeressed to a dead miss. Had autozone check codes and it showed #1&#6 were miss firing. Orginal plugs & wires no sweat, replaced them still missing but only when cold and only at idle. I'm out of state without tools so go to local Ford dealer.
They say #1 & #6 missing but it also has a lean code. They say bad injectors. 2 days - 2 injectors - new intake gasket and $400 dollars later it runs the same. Then they say the bad injector has screwed (damaged)the processor! They prove this by ground the injector and engine smoothes out. Well I figure I'm the one that has been screwed.

Drove 800+ miles home at 70-90 and it ran fine only missed when I stopped for fuel, then went away once back at speed. Have taken it to my local (fairly trusted) to have them fix it right. But would like to have any info anyone may have or suggest.

 

I feel your pain, from the sound of it, I am experiencing the same problem.
Mine started with throwing a couple of codes for left and right banks running lean - replaced plenum gaskets and it runs much better but far from fixed. I still have a misfire on No.3 and No.1 and No.6 are not firing I have replaced plugs, wires, coil, cam poistioning sensor and I am sure there is more.
My other truck is in the shop for warranty work and told my service tech of my problem, he had me do a test on my injectors, sure enough No. 2 and No. 6 injectors are not firing, told him the results and he told me it was the PCM.
So I am not sure of what my next move is going to be, My Service Tech is really sharp, One of the best I have ever had and I don't dought he is right, But I am leaning towards paying some one to confirm it, so I am not just throwing more money at it not to fix the problem.
Keep me posted on your progess and I will do the same.
Good Luck,

 

Just wondering.....

Did the dealer get the problem resolved? If so, what was the fix?

 

Not yet! I went by this morning to see what they had decided. They have tried everything and are at wits end. At this point they have had to repair the poor quality of work from the Kentucky dealer. The Mechanic that changed the injectors broke the retainer clips on the injector plug in and had probed the wires with a test light to the point they were almost broken!!!
They are pretty good people and are trying hard so I give them some more time. I already told them I was not paying for training.

 

Ford dealer says #1 cylinder has 170 PSI with manual compression test (engin not running), but has no "running" compression. This is the first I have heard of a "running" compression test. I am not familair with the internals of the 4.2 or the "new" engines. If I am not mistaken the 4.2 has cam, hydr lifters-push rods-rockers arms. My toughts are the only things that could cause no running compression would be a sticking valve-weak spring-colapsed lifter. But it seems these would cause an engine noise "ticking" or at least the would on the old style engines(302-351-etc...). Also my problem is better at WOT or 1/2 throttle.
I guess its time for this old timer to come up to speed on these new engines!

 

I do not think you are mistaken with your understanding.

This is interesting.

Sounds like time to pull a valve cover off and start nosing around.
Keep us posted.

Thanks!

 

SNAP!!! Broken valve spring on #1 exhaust valve! Two weeks, countless hours of Tech, Svc Manger, e and finally Ford Factory tech on the line. I only took it to them because I thought it involved the computer/ignition/fuel system! Bottom coil broken making spring weak but no noise (clattering) other then the miss!
They are happy to eat it all, except 2 hours of troubleshooting, which was my suggestion.