Hey guys,
Have a weird issue I think I know what it is but want to verify. I was leaving work, eased into the throttle it stumbled, did it at every light no matter if I was light throttle or WOT it. The truck would pick up after hundred feet or so and go but would start spark knocking under medium to heavy throttle.
What I have checked:
Swapped from rear to front tanks- no diffrence.
Cap and rotor- had some corrosion flaked it off, no diffrence, did notice white spotting on pick up coil tone ring.
Did compression test- 180-185 all cylinders, engine hot still when tested.
Put timing light on all cylinders- All lighting up, couple seemed a little slow or had a skip in cycles. Tune up parts done less than 3k miles ago, brass terminal cap and rotor, Taylor thundervolt wires, motorcraft platinum plugs.
DLC test-OOOO pass. Fuel trims were -7 on I believe pass side, I did not pay that close of attention to it.
Fuel pressure-30psi at idle jump up throttle 41psi
Back and forth on dampener bolt- timing set is nice and tight as I start to go either way rotor follows. Also when I had upper intake off before for gasket, pulled pass. side valve cover no sludge no nothing looked really good could still see paint mark on valve springs and it has 181K on it. Plugs always end up looking better on inside than outside thing burns clean.
After tests, took it back out no more stumble but still spark knocking pretty heavy, with just enough throttle to get it to kick out of OD at 45, cycle key off enough to kill engine and back on while driving and can WOT it no spark knock, sitting in gear will break tires loose never spark knock.
pick up coil advancing too much? I have timing set to factory notch not advanced at all from factory.

Thank you, greatly appriciated.
Curtis

 

Update, went out for lunch fired it up really slow on rev, stumbled until 1000rpm then took off. Going home 2 hours later did not stumble, just bad spark knock until up to temp then I could WOT it at any speed nothing just smooth. Scanned tps is in range, reman EEC is less than 4 months old, has been wet out but never gave me fits like this before.

Thank you
Curtis

 

R&R pass. pre cat. o2...another post of mine I answered my own question.

 

So was it the o2?