Dannyi

This story is a bit lengthy so please hang in there. My son wanted to do a tune up on his 97' F150 4.6 V8. Said it was running a little rough, other then that it was fine. We change the plugs and also installed new plug wires. I decided to remove the fuel rail on the right side to make it easier to get to the 2 rear plugs. After we had everything back together my son started the truck and it idled ok but still a little rough. He took it for a drive and came back to inform me it ran horrible! Very little acceleration and misfiring like crazy. One of the first things we did was check the firing order, that turned out ok. Then the injector wires and plugs, all were on the right injectors and secured. He took it for another drive, same thing. Because I pulled the fuel rail on the right side(2 injectors came off with the rail and 2 didn't) I decided to pull the injector wires one at a time while idling. The first cylinder when pulled made a noticeable difference, the next 2 cylinders, I believe #3 and #5, made NO difference. The last cylinder also made a noticeable difference. Thinking that one of the injectors might have gotten clogged or damaged we switched the #1(known good one) and #3. Same problem, #3 and #5 cylinder, still no difference. Pulled the spark plugs to find them very sooty already. Thinking now it's an electrical problem, I checked the voltage at the injector plugs and for spread terminals. Terminals ok, and each injector plug had 14.34 volts on the power side terminal and 0.03 volts on the signal side terminal. We're also getting fuel to those injectors from the rail. At this point we have to admit we're stumped! New plugs, new wires, right firing order, power to the injectors, fuel, and the swapped injector test. Is there something we're missing or not aware of? Something else we should be looking at? Any ideas or help would be greatly appreciated........thanks guys.....

Bart

You may still have a bad plug or wire. Any time you use aftermarket anything you run the risk of problems. Make sure you have not cracked a plug. Make sure your wires are up to spec.

rtg143

You could try swapping coils to see if one went bad. What kind of plugs did you use? Here's a diagram in case you need it.

Kattumaram

Plugs 3 and 5 are fired by coil 2 on the right side of the engine. Swapping the coils should move the misfire to two other plugs if the coil is bad. If the misfire continues at 3 and 5, then the circuit between the EDIS-8 module and the coil needs attention.

Dannyi

...thanks fellas for all your help! After we got the correct firing order diagram it turned out to be just that. #2 and #3 were wrong. It looks like I just over thought this one. Having the correct information sure does help!..............thanks again guys!!

rtg143

Thanks for the update.