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Q: FLASHING CHECK ENGINE LIGHT on 1998 Ford Expedition

WHILE driving,especially on the highway, my check engine light which is already on begins to flassh. trying to find more likely reason.
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I own the same truck. Had same problem. The OWNER manual states, steady light usually an emmision problem. Flashing Check Engine light means a miss-firing cylinder. This can cause damage to catalytic converter, etc. Check plugs, wires, etc. My problem was a bad wire to cylinder # 4 (Most difficult plug to reach I have ever encountered) A miss-fire can and will also damage the coil. (didn't fix soon enough) Replaced wire and coil, and of course changed out all the plugs. Either reset check engine light with a scan, or drive 20-30 miles and if you did good, the light will no longer flash. Good luck. Denis
Hey I have a 98 expedition I have had three people look at it and paid for three diagnoses to still have the Same problem #4 cylinder missfire did all plugs and wires but not the coil on the my truck there is two one on the passenger and one on driver when I picked it up from the last guy there was no light as I got on the freeway the engine light came on and started flashing I finally just took it to Autozone and it says the same code #4 cylinder missfire can it be the coil I am almost thinking of takin it to ford but didn't want to spend 130$ for them to tell me #4 is missfire when I know that what's the best cheapest way to fix this issue? It also gave me a code about ho2s1 switching and low input someone help please thanks ,Nick
This is a very serious failure of the emission control system on your vehicle. Have it diagnose ASAP by a qualified technician.
You need to have a shop scan for codes to determine what repair is required and you can locate a shop near you here and once they determine the repair you can check prices here
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