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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 35824
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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2006 F150: misfiring..cylinder..all the spark plugs and the coil pack

Resolved Question:

I have a 2006 F150 4X4 that is misfiring on cylinder 7.
We have replaced all the spark plugs and the coil pack.
We replaced that fuel injector too.
We are still having the issue. Can you help?
Submitted: 7 years ago.
Category: Ford
Expert:  Ron replied 7 years ago.



Thank you for asking your question on JustAnswer.


If you are sure the spark plug is good and the coil is firing as well as the injector is pulsing, then I would suspect you eaither have a compression issue and or a vacuum leak on the intake at the runner. I would start with running a compression test on that cylinder.


Customer: replied 7 years ago.

Hey Ron,


We tried that, but the compression tester we have doesn't fit the hole.

Is there an adapter or something we can buy to make it fit?


Expert:  Ron replied 7 years ago.
Yes , you will need the deep threaded one that matches the spark plug. They come in the compression kit.
Customer: replied 7 years ago.

So where can I get that from?

Do I ask for a compression kit?

What is in the kit?

Expert:  Ron replied 7 years ago.
Most part stores will rent you the compression gage set. It will have the right fitting in it with the gage.
Customer: replied 7 years ago.

I called my brother and he said he got the adapter and ran the compression test today and it appeared to be fine.


Expert:  Ron replied 7 years ago.
Ok if you have good compression, good spark and plenty of fuel and no vacuum leaks, the cylinder should fire. You need to go back and recheck all the above. Something is being missed here.
Customer: replied 7 years ago.

So it has to be one of those things?

Spark plug, coil pack, fuel injector, or the compression?

Expert:  Ron replied 7 years ago.
Yes or you have a lean engine due to a vacuum leak on that cylinder, go back and recheck all of the above.
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