i have a 98n expedition 5.4 triton replaced timming tensoiners because it was making so much noise. replaced all the plugs and coil packs now it has a rough idle and can be felt some when on the hiway


Asked by Aug 17, 2016 at 06:38 PM about the 1998 Ford Expedition 4 Dr Eddie Bauer 4WD SUV

Question type: Maintenance & Repair

did not have rough idle before all the plugs and coil packs and timing tensioners were replaced. took it to ford they say it has low compression on driver side.

7 Answers


When replacing spark plugs it is very easy to pick up some oily dirt that can get between the gap or the gap can get closed if plug is dropped in spark plug hole. So I would remove plugs on drivers side and take another look at them.

Bob Beaman

Is the check engine light on? If so get it scanned for codes at a local auto parts store. What brand were the coils? Genuine Ford - Motorcraft is the best and some of the aftermarket stuff is crap. If a dealer says low compression on the driver's side is it possible that the cam timing is 1 tooth off?


Bob no check engine light . it ran good except for the knock from the timing chain . after replacing the chain and coil packs and plugs it now run a rough idle . used the accel super coil packs and motorcraft plugs. engine dose not have any knocks now just rough idle. checked the iac and mafs and the throttle body


also tried pulling each coil pack wire off to see if it would make a difference in the idle and all 4 did make it run a little bit rougher. just cant figure this one out

Bob Beaman

If you are sure the issue is on one side of the engine you could put 4 of the original coil packs back in on that side if you still have them. That would be a royal pain in the butt swapping them out. I personally would not have used anything Accel makes on my truck, some have good luck with Accel and others don't. Does it smooth out just above idle?

Bob Beaman

Interesting read on coil packs at the link....http://www.f150online.com/forums/v8-engines/257269-accel- super-coils-02-4-6-a.html

Bob Beaman

More reading here.....http://www.justanswer.com/ford/5lpy6-ford- mustang-gt-just-replaced-timing-chains-tensioners-chain.html

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