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Mercury
Grand Marquis
47

Misfire due to failed spark plugs or ignition coil on Mercury Grand Marquis

Problem Description and Possible Solution

Bad spark plugs or an ignition coil can cause ignition misfire, which will illuminate the Check Engine Light.

Problem Data
RepairPal Verified
Average mileage: 143,214 (52,000–217,000)
Engine affected: 4.3L V6
9 model years affected: 1996, 1997, 1998, 1999, more2000, 2001, 2003, 2004, 2005
47 people reported this problem
Comments
Viewing 1 - 15 of 15 comments
Had a stalling problem, that went away, now it chugs and has a misfire, plus gas caused the stalling when I went back to regular it didn't stall, P0304 cylinder 4 misfire.
one morning the check engine light went on and the car rode rough. I figured bad gas or fuel filter. 2 miles on the check engine light started blinking. Call to mechanic told me to get the car to him ASAP. Drove 6 miles home going 10mph on the shoulder, praying all the way. Bad ignition coil. He replaced all the plugs. Got off cheap, could have been catalytic converter or worse. Otherwise great highway car.
Misfiring plugs or coils. Advance Auto put a tester on it and said 2 of my coils were misfiring. I am in the process of changing the plugs and all the coils. I found 8 coils online for 125.00 new. The car has 256,000 mi on it
Having misfiring from plug number 4. It happen after putting gas in car. It ran great until I filled it up.
Check engine light came on. Did tune up. Check engine Light on after week. Checked at auto zone indicates ignition coil is the problem now
Misfire during highway driving and going up a hill. Went to local mechanic to verify autozone codes, cost $60. Went to autozone and bought coil pack for $68. Fixed with buddy.
Took the car on a 1,200 mile road trip, about 400 miles left on the return home the car started to vibrate / chug. I wasn't sure if it was a fuel or spark problem or if it was the transmission. At first it was very noticeable while accelerating over 55 MPH or while going up hill, the transmission seemed like it wasn't sure if it wanted to be in overdrive or lower. I assumed it was a lockup torque issue. The odd part was I could kick down to a lower gear (accelerator to the floor) and the engine would seem to smooth out. That's why I assumed it was a transmission issue and not a fuel / spark problem. The further I drove the worse the engine ran, even now it runs poorly at idle. I just got into the shop and they tell me the codes say there is a misfire on cylinder 1 and 8. I believe it is an injector issue due to the fact that the issue is progressively getting worse. I believe if it was a coil pack (spark) it would pretty much remain the same at all times. Guess I'll know once it is fixed.
When driving over 60 miles/ hr, noticed hesitation in running, took to deal who confirmed two coils and spark plug need to be replaced