tritonbullet

My 92 has developed a P0300 after a tune up, new copper plugs, wires, cap rotor but after it's warmed up once you START to drive the CEL comes on. Light won't come on if you just let it run in park but once you start driving boom there's goes the light. I'm thinking maybe the 23 year old ignition coil is bad??

Has new upper intake gaskets too and everything up from there, I'm out of ideas.

tritonbullet

Put a new coil on today, still has CEL when it gets up to temp.

Chris_1

iTrader: (1)

Did you route the spark plug wires according to Ford's instructions ? Not doing that can give you a crossfire (especially under load), which would give a random misfire code.
Just a shot in the dark there.

tritonbullet

What is ford instructions? I looked online and got a diagram off there. But it wasn't a ford site

broncojunkie

Your '92 is obdII?

tritonbullet

Nope obd1 but still had that "code" pop up when scanned

tritonbullet

Who knows the correct spark wire routing??

Chris_1

iTrader: (1)

Mine's 95 which has the HO firing order - yours will be the standard firing order so it will be different from mine.
Basically some of the cylinders that are beside each other fire one after the other so those wires have to be well separated from each other or they can crossfire. Big enough of a problem that Ford put out special instructions on routing the wires. My 95 even has a sticker under the hood showing the proper routing.
Not for sure that's your problem, but if you just line them up beside each other in order, it could be.

tritonbullet

My looms on valve covers broke so how should I seperate them??

fltdriver

Do not put wires from cylinder #s 1/3 & 5/6 next to each other in the wire separators. IF you don't have wire separators they are all but free at a junk yard or I'm sure you could find something that will work in the HELP! section of an auto parts store, or make your own. Those being together could cause you to have some issues.

As for your problem: that (p0300, 300, or even 30) is not a valid code for your year of truck. Those readers don't seem to like OBD1 fords for some reason. Pull the codes manually following the sticky on the main 87-96 page. I would be willing to bet that you get a o2 sensor related code.

My guess is your CEL comes on after a few minutes of driving then goes away every time you restart the truck. You either need to change one or you have damaged wires or connector not fully seated somewhere. I had an issue with one that is directly behind the battery throwing a 172 code that drove me nuts tracking it down.

Usually a running issue (misfire, no detonation, etc...) will keep the CEL illuminated regardless of restarting but a o2 code won't.