93 f150 5.0 intermit misfire and spark knock

scott1984 · February 13, 2013

Guys this thing has me pinned hard against the wall. Its a 93 f150 with 5.0 e4od trans. Once it is up to running temp with tcc engaged it goes to spark knocking and misfiring but unplug the spout shorting bar and runs fine. i have check the module and ecm also replaced with a know good ones.

batmantech · February 14, 2013

I would guess that you have a worn bushing in the distributor housing or stator problem. It has been a long time since I did one but it was a fairly regular thing back then. I think an aftermarket distributor was cheaper than the staor pickup.

Aaron · February 14, 2013

Is the base timing correct?

Brad Clayton · February 15, 2013

Like Aaron suggests, check base timing with spout unplugged, it should be 10 degrees. I have backed them down to 6 degrees to cure spark issues in Town Cars. You need to see if the computer is controlling spark advance correctly and that will require an NGS or Super Star II tester or something that can do a KOER test. With the spout plugged in, the KOER test will advance the timing 20 degrees.

scott1984 · February 15, 2013

base timing is @ 10 without spout and it does do fine until it goes in closed loop and the shaft is good little to no play i put a pickup in it thinking it was screwing up but i not scared to try a another dist.

BrunoWilimek · February 15, 2013

Just a thought, but did you happen to check for timing chain wear? With dist.cap off, rotate crank pulley clockwise/counterclockwise to see how many degrees of crankshaft rotation are possible before rotor turns. I think the maximum tolerance was 5 degrees.(if memory serves me correctly) A vehicle this old may have excess wear on the chain and pulleys.

scott1984 · February 18, 2013

Just normal wear truck only has142,000 miles road but i did check it but everytime i think something mechanical i go back yo the spout connector

mrbudge · February 19, 2013

If it is only when the convertor is locked up, make sure #7 and #8 wires are not routed together. Since they are consecutive in the firing order they can crossfire under load, and since #8 is using #7's spark it will be way too advanced on that cylinder. Eventually the piston will burn if nothing is done.

scott1984 · February 21, 2013

ok guys little update on this thing i pull the dist. cap off and checked play for the bushing "as per batmantech" found up and down as well as side to side play. Replaced with reman one and problem is FIXED. Thanks guys for all the help.