1998 Expedition Engine Rough

[tim6171]

The engine on my 1998 Expedition has suddenly begun running very rough. It varies day to day in severity, but it is worst when idling and gets better as it runs up through the gears. Since it first started about a week ago, and a couple times has run fine, but all other times its quite noticeable. Very rough rumbling and shaking.

Engine is a 5.4 V8, Eddie Bauer (not sure if that matters). 180k miles. Engine light is on, but not blinking. It did go off for a day or two, but came back. I don't have error codes yet, which I know would help. But I am hoping you guys can maybe give me a general idea of what the problem may be. No other problems on the engine that I'm aware of save for a small timing issue in the transmission.

 

[thenaaks]

I'm guessing coil pack. Check the codes.

 

[Bedrck47]

when were the plugs and coils last changed Check for vacuum leaks

If the check engine light is on it should be throwing a code.

Check fuse #12 in fuse box under the dash That is the fuse for the OBD II connector

 

[98EXPnSRQ]

Check the EGR valve, that would be my first guess. Pull the vacume line and put 20-30 psi of vacume on it at idle. If it is working, that should make it idle very rough. If it is stuck open there will be no change when you add vacume.

 

[Dukester]

Faulty O2 sensor can cause this as well.