F150 Rough Idle and Popping Sounds

[Musky_Madness]

I have a 97 F150 4.6L V8 with 123k miles. I recently brought it to a local Ford dealer to have the oil changed and upon driving it home, the engine began to make "pop" sounds and would hesitate like it is misfiring. When stopping at a light or intersection it idles rough and shakes the whole truck. No check engine light has come on and idles normal in park. I have run Sea Foam through both the gas and oil, have fresh gas in the tank, tank of gas had HEET in it so water should not be a problem. I run intake/fuel line cleaner through it regularly and have used Restore in the oil during the last oil change. I brought it back to the dealer and they don't know what is wrong and will have to have a tech look at it. Any suggestions?

Thanks for any input.

[Shack]

My first guess would be a (or more) COP (coil over plug), but that is just a guess. They will need to scan the codes first to know what is going on.

[Tom7227]

Broken cearmic on a spark plug? Happened to me once on my 97 150 and I thought it was going to die on me. It was intermittent. My fault as I cracked it changing the plugs.

[fishing tech]

It has been a while, but a 4.6L should have plug wires??? Wires are pretty common problem with that kind of mileage if they haven't been replaced.

[Shack]

I believe 1997 was the first year Ford changed the 4.6l over to COP.

[Musky_Madness]

I was going to change the plugs over the summer and after looking at the acrobatics required to do that on my own, and lacking the tools to make that work easier, I didn't. What codes could the dealer check if the check engine light isn't on? How about compression...? I was doing some researching on here today as it has been snowing all day and found that maybe one of my cylinders has lost compression? What a headache right after Christmas.

[Jeremy airjer W]

Was the brake pedal hard?

I think I'm going to go out on a limb and say broken valve spring (worst case scenario)?

[Scott K]

The 97 4.6 has plug wires. I would be thinking a bad wire or plug, because it only does it under a load. Not at idle

[HondaRider07]

Get it scanned at a local parts store. It may be have a CEL on yet, but it will store codes(pending) for any misfires it sees. It is a misfire under load, so like stated above, guessing plug or wire. You could get someone to get in the front seat and put the trans in drive while holding a foot on the brake. Then disconnect the injectors one by one(reconnecting each one before disconnecting the next). Listen for the injector that you disconnect without a change in rpm or engine idle. That will be your suspect cylinder. The rest will cause a significant change in idle, because you will be dropping 2 cylinders. inspect the plug and wire for any damage.

[Shack]

The 97 4.6 has plug wires. I would be thinking a bad wire or plug, because it only does it under a load. Not at idle

I am sure you are correct 4.W.E. and fishing tech. I thought them where on 4.6l in 97. I thought they ran from 97-05.

In that case, I would check into the wires first.

[Scott K]

Shack, FYI the 5.4 started off with C.O.P.'s in 97, but the 4.6 had wires strung around the engine like a spider web!

[Musky_Madness]

Well I brought it in and it is an issue of the spark plug and the wire assembly leading to it on cylinder 1. All said and done $175 to fix her up today. Nice to have it smooth running and power back! Way to nail the problem!