I have a 2000 Grand Marquise 4.6. It runs well when cold, once warmed up it runs rough.

30

Asked by Jan 07, 2017 at 05:55 PM about the 2000 Mercury Grand Marquis LS

Question type: Maintenance & Repair

I had changed the plugs hoping this would solve the problem, it did not, though the plugs were in sad shape.  The only error code I am receiving is a misfire in #2 cylinder.  I listened to the injector it sounds consistent with the others.  Should my next step be to replace the coil pack over that one spark plug?  I've never experienced a coil acting this way.  I realize some things are a process of elimination, but I don't want to just throw parts into it.

7 Answers

77,905

P0302 MERCURY - Cylinder 2 Misfire Detected.... Possible causes - Faulty spark plug 2 - Clogged or faulty fuel injector 2 - Faulty ignition coil 2 - Fuel injector 2 harness is open or shorted - Fuel injector 2 circuit poor electrical connection - Ignition coil 2 harness is open or shorted - Ignition coil 2 circuit poor electrical connection - Insufficient cylinder 2 compression - Incorrect fuel pressure - Intake air leak

2 of 2 people found this helpful.
30

Thank you for your insights. I will press in this direction. You have been a big help. Thanks again

1 of 1 people found this helpful.
30

So, In my situation, I replace the coil for the #2 cylinder. I cleared the code, took it for a test drive and drove with the live data stream hooked up so I could make sure the engine has reached it normal temp range. It ran great....smooth all the way around. Thanks again Rowefast.

1 of 1 people found this helpful.
58,205

You should have replaced all coils with Motorcraft coils. You likely will have problems again as this is a common issue with these cars. Using aftermarket coils is a hit or miss proposition. Sometimes they work and sometimes they don't last very long.

2 of 2 people found this helpful.
77,905

Your most welcome puzzled2...

30

Thank you Bob, I agree with your comment about replacing all the coils. I don't like doing things over. We have had a lot of repairs the last couple of months and our car funds were depleted. I did buy a Motorcraft coil though. Thanks again for your thoughts.

1 of 1 people found this helpful.
58,205

Good, Motorcraft although expensive is the best part for this application. Best of luck with it.

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