I have a 94 F150 4.9L inline 6. Started cranking w/ ruff idle at intermittent times. It would run good for a week then abruptly crank ruff and set codes 112,117,122,126,327,634,638. I ohmed out ACT (112) checked good,I ohmed out ECT (117) checked good, tested TPS (122) no flat spots, replaced MAP sensor (126), cleaned EGR although it was not dirty and replaced w/ new gasket, also pulled,cleaned and checked IAC assembly. Still the same intermittent problem. Found out thru trial and error that when it cranks ruff and sets codes there is not 5 volts (vref) going to TPS and MAP sensors instead there is only .5 volts.Tried switching relays from EEC with horn and fuel pump relays.. Doesnt seem to matter sometimes when u turn the ignition key there's 5 vref volts at the sensors and sometimes theres only .5 volts.

The Ignition key assembly is loose and can be cranked with any Ford key ( been that way since I got it from a friend 4 years ago with no problems) although I have the original key and have used it only. I'm Stumped!! Any Ideas?

I'm thinking key/lock assembly, Maybe bad ignition switch because of intermittent voltage at sensors , or bad EEC? Any ideas or help would be greatly appreciated. Thanks in advance.

 

Here's a page you might find useful. http://fordfuelinjection.com/?p=3

 

Thanks for the reply. I've already ready that along with many other threads. I pulled the EEC over the weekend and found 2 of the blue capacitors burnt, so I'm thinking this is the problem. Got a reman ordered should be here Wednesday. Hopefully this will solve it.
Does anyone know what would cause the EEC Capicitors to burn?
I don't want to burn up the new remanned one.
Thanks

 

UPDATE!!
Replaced the EEC Wednesday w/ a reman. Runs like new so far w/ 230,000 miles on it.Gonna replace plugs cause they were black w/ carbon from all the gas from sensors not gettin vref voltage. Hopefully this will be the end of this thread.