t_haynes

Hello and thanks for reading.

I have a 1999 Mercury Grand Marquis which I recently bought used with 120K miles. The check engine light came on, and it was missing badly. I took it to a guy who read the code and said it was a misfire on #4. He replaced the coil pack and the plug on #4.

All was great until about 20 miles later. It seemed to be the same thing with the bad miss and the check engine light. I went back, and this time the code said it was a misfire on cylinder 5. He inspected the coil pack, and checked the plug. He cleared the code and said all was well.

I still have the bad miss, and the check engine light is on again. Do you have any suggestions for me about how to fix this?

Bert

Did he see if the other plugs needed replacement? It could have another coil pack problem. You can move the offending cyl. coil pack to another location, (one that's easier to get to), and see if the missfire move with it. Autozone will check the codes for free. Another thing to do is, clean the MAF with the MAF cleaner.

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Bert

t_haynes

I think I will try the autozone read codes for free. Would you suggest replacing this Coil on Plug Boot by Autolite - Part 50003 - Advance Auto Parts on the problematic cycliners?

Bert

Those are just the boots for the coils. If it needs a coil, the boot comes with it. The boots could be bad but more than likely, it's the coil itself. Check our sponsor Rockauto, they give a discout to our members. Look down the forums to the sponsor section.

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Bert

t_haynes

I installed a new coil pack when Advance Auto opened, and I got them to clear the "check engine" light. The only code in memory was the misfire on #5, and it seems to be completely fixed now.

Thanks for the help.

Bert

Thanks for the update.

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Bert