https://www.ford-trucks.com/forums/6...stic-quiz.html

Not much interest in playing the game, so here is the answer.

...The problem appeared to be injector realted although why things suddenly got better at 170F I could not figure. I figured I'd start troubleshooting at the perimter and work my way toward the injectors, hence the checks I previously noted. Next steps were going to be the wire harness connections under the valve covers and looking at the IDM.

Then I remembered something I'd read here about the ICP and the default operating tables. Great source of info this sight is. So, I unhooked the ICP, the truck threw the appropriate code, SES light came on and she started purring like a happy 7500lb kitten again. Plugged the ICP back in and the miss returned.

Long story short - A week of driving on the default tables, $50 ebay bucks , and a 5 minute fix and the problem is solved.

My guess is I had a solder joint going bad in the original ICP. Cold solder joints are temperature sensitive so it might make sense..?

Also, since installing the new sensor, the truck idles 20 RPM lower and oscilates 2-4 RPM where *** the old sensor oscillated 5-7 RPM.

Not sure if there is a lesson here other than to take advantage of troubleshooting freebies, like the ICP default table, and the wealth of knowledge on this sight.

Regards,

Mike

 

Thanks for the update, good info for future. Glad you got it figured out.

 

Never would have guessed at that. Never.
A single cylinder cutting out because of a bad ICP sensor that controls all eight?
Methinks you might have a weak injector that is hiding behind a good system now.

 

I hear you... I just don't like what I am hearing... What do you think of the theory that a flakey ICP might send out a "random" bad signal effecting whatever cylinder happens to be firing at the time??? The perfect operation above 170F also haunts me...