Replaced the leaking caps in mine, or rather my local tv repair man did (charged me 25 bucks, wasn't worth messing with it myself for that price) correcting a system lean code.

A system lean a condition it did not suffer from.

Replaced caps = no more 172 system lean code.

And yes it had suffered system lean codes a time or two prior in the years I've owned it, corrected by replacing the O2 sensor. Done so of course after first checking/testing for conditions and eliminating those that could otherwise cause lean condition not attributed to a faulty sensor.

Came to a point the code would present with no reason for it, lead me to suspect the PCM.
Found PCM to have one badly leaking cap so had all three replaced.

Replacing caps on a board isn't rocket science and is easily done with simple cheap solder iron (believe I paid 18 bucks for the one I have now, small 30-35watt iron available at most any hardware store).

Then need new caps of course and the proper solder for the job (not the same stuff you use to sweat copper pipe together) both easy to get.

Hardest aspect of the task..at least for me at first.... was removal of the old caps clearing the board for new parts. Easiest way I found to remove old solder is with a shot of compressed air. Solder vac works too just don't happen to own one no real reason to buy one now after finding air works so well, quick shot of air leaves a nice clean clear hole each and every time no muss no fuss rendering solder tape I tried at first a waste of time and useless to the task.

If never done it before I would suggest practicing on a dead mother board of some sort first before diving into your trucks computer, remove and replace a couple caps from an old dead board first. Gotta believe everyone has a dead electronic something or other laying around to use as a gunny pig to practice with first if/as necessary before repairs on something that matters.

 

Alrighty then..................... I sent ECM out to be rebuilt, got it back and installed it, truck runs a little better but still the same problem.

 

Did you try running the KOEO tests and CM display again?

 

All tests good now.

 

Then you most likely have a sensor sending wrong values to the computer. Even though you may be passing the KOEO, CM and KOER tests you can still have a bad sensor.

Sensors to suspect: ECT, ACT/IAT, MAP and I would also verify the TPS signal.

Good info here on each sensor, how it operates and expected values: Fuel Injection Technical Library

 

Has there been a fuel pressure check anywhere? I didn't see mention of such.

Be nice to see if there was difference in cold/hot operation pressure.

 

Tested sensors, all test within specs. I went ahead and replaced O2 sensor (was the original one), fuel pressure regulator(thought it was bad) and TPS (right on limit of specs) and no change in true problem. Fuel Pressure test is at 56psi and 53psi running down highway. FP does not drop off (have not tested over-night).

 

If all the inputs are good, according to your statement "Tested sensors, all test within specs.", then the only common denominator is a bad computer. If it truly is too far advanced timing then pulling the SPOUT eliminates the computer from the equation. The Ignition Control Module will fire on the raw PIP at the base timing determined by the physical position of the distributor.

 

Possible temp sensor, the upper one.

 

OP already stated "Tested sensors, all test within specs."

 

Yeah and? Did he wiggle test? Did he physically remove and test? Air temp sensor is a very important sensor.

 

I am taking the OP's statement at face value and simply pointing out what they have already posted. If they said they tested the sensors already then why would anyone need to state again it could be sensor X or Y?

While I do agree with you and I already stated the key sensors, I am not going to beat the OP up by questioning their methodology.

 

Yes, I wiggle tested, and no I am NOT taking every sensor out and "bench testing" them, if I do that I should just replace them. I went so far as getting a junkyard computer so I can have at least 2 to use. No change. I do not have access to a fuel flow tester and the nearest garage I can find with one is over 2hours away. I am getting the truck towed to there and do a flow test.

 

Maybe the timing actually IS really advanced.

Harmonic balancers are 2 pieces, held together with a rubber band between them. When they get old the outer ring can slip from its original position, this will put the timing marks off from theit actual position.

You can check this by pulling the valve cover and spark plug, finding TDC of #1 and comparing it to the marks on the balancer.

 

Base timing check/set (Ford caused some confusion unfortunately):

https://www.ford-trucks.com/forums/3...ing-marks.html