Question about 1998 Ford Expedition

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I have a 1998 Ford Expedition 5.4l, engine has an intermitent miss-fire and hesitation after reaching operating temperture. I have no CEL or stored codes. This problem is much worse when the A/C is on. I can feel the miss while stopped at a traffic signal. I have replaced the plugs, coils, fuel & air filters, TPS, cleaned the MAF sensor. Seemed to stop for a while then returned. Runs fine until engine warms up?

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Your good
I would still remember, that all ford COP Coils have issues,from 1998 thru today
The Coolant Temp Sensor, should put it into closed loop, after it warms up---then the O2 Sensors can do their thing. That's one item
O2 Sensors slow to swing--maybe,need to test
Converter partially blocked-a bit of a stretch, but don't rule out.
I would buy one new coil, and walk it down from cyl to cyl,tough on that engine,but I put my money there

Posted on Oct 02, 2010

  • amain Oct 02, 2010

    Thanks, I'll give that a try. I love the truck but these engine missfire problems are a PIA.
    Most times I hate to see a CEL, right now I wold love to see a hint from the computer! Would a software update to the computer help with this? Thanks again


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My expedition was doing the same I also cleaned the maf sensor I had to end up changing the maf to a new one and fixed the problem.

Posted on Nov 02, 2010


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