Cylinder 4 misfiring

[Vixxster]

I have a 2004 thunderbird. I am having an issue with cylinder 4 misfiring, but cannot find the source of the misfire. Anyone with experience with this

[007Cruiser]

Quite possibly a bad Coil-on-Plug (COP). This is very common. Coils are available at many price points. Instead of just replacing the bad one, you may want to do all four on that engine bank. This should save you future labor expenses when the others fail.

[Vixxster]

It appears that the valve is stuck, but it is still to be determined why.

[JerriLampon]

What ODBII code is it showing?

[BillyL]

This is a first time to hear of a stuck valve on a bird? Sounds serious and expensive. Sorry to hear, please keep us informed of the outcome.

[007Cruiser]

Yes this would be the first stuck valve reported here.

[5bird7]

Vickie, What have you or your mechanic done so far to determine that it might be a stuck valve?

Have the coil and plug been replaced already for that cylinder? That is the usual and most likely cause of one of the cylinders mis-firing.

If that has been done, then it could be that the replacement coil is defective.

Has there been an oil problem with the engine? How many miles on your tbird?

[007Cruiser]

All good questions

[Brad]

I had an issue, where replacing the COP on the cylinder reporting the misfire did not correct the problem however changing all of the COPS did.

[HKS]

It appears that the valve is stuck, but it is still to be determined why.

A stuck valve should make a difference in the engine noise. Should be able to hear it with stethoscope.
Or a rod transmitting vibrations to your head from the valve cover like in the old days. Like the engineer was doing in "Das Boot" he used an old valve as a rod.
HKS

[Tbear]

I had an issue, where replacing the COP on the cylinder reporting the misfire did not correct the problem however changing all of the COPS did.

I had the same problem with a misfire on 4 and just like Brad, I replaced all the COPs and plugs. That fixed it.

[EllisonCal]

Yes this would be the first stuck valve reported here.

Sounds like the "water intrusion" BS, that ultimately turned out to be one of the new coils was "bad". This diagnosis was after I had all 8 coils, plugs and rubber sleeves replaced.

[Elky64]

A stuck valve can be proved by old fashioned methods...such as compression test or leak down test.
Also many more mechanics should be familiar with these than all the electronic gymnastics now necessary on newer vehicles....
Al

[BillyL]

I agree with all above posts. First, I would get another mechanic's opinion. 2nd,I would try changing all 8 coils and plugs, while doing manual compression tests while changing out plugs. I simply cannot accept a stuck valve as cause.

[HKS]

A stuck valve can be proved by old fashioned methods...such as compression test or leak down test.
Also many more mechanics should be familiar with these than all the electronic gymnastics now necessary on newer vehicles....
Al

Al,
You are right. I forgot the obvious "Compression Test".

Can't do that on a WWII diesel submarine engine when it is running.
HKS