Cylinder 4 misfire and events

[jgrathoff]

I am currently having this same problem with my 98 Expedition with the misfire code P0304, also was told that my fan clutch bearing is cooked as well. I do have a mechanic friend working on my vehicle. while the misfire was happening my check engine light was blinking as well

 

[hades02]

Just posting my experience. I had the same issue (97 4.6). Turned out to be a loose #4 plug. Tightened it and the problem went away. Several months later the problem returned. I could not figure it out. One day she started bucking hard and the CEL started blinking. Then steam came from under the hood. The heater tube that goes into the manifold had finally cracked and coolant was leaking onto the #4 plug again. Perhaps you have a slight leak in that area. Have you pulled the wire and checked for coolant pooling in that area since you cleaned and reinstalled the plug?

 

[ZeroData]

hades02 I have no leak there anymore. That was cleared up the night that this first began. I have changed all the plugs now and the plug wires. The problem still exists. I have removed the plug wires one by one and the only one that does not affect the engine is cylinder 4. The odbII graph still shows a misfire on cylinder 4, but not any of the other cylinders. Due to the weather and my work schedule I have not had time to run the compression tests I wanted to.

 

[ZeroData]

I was able to run a compression test today. I get between 154 and 167 on all cylinders except number 4. That cylinder has 0 psi compression. Tuesday I will be pulling the valve cover to look at it and pull the head if needed.

 

[kyle_in_rure]

I'd say it's time to change your plugs and wires. I had the exact same thing start happening on my 97 with 185K on it (original plugs and wires, I found out later).

Replaced plugs and wires and I'd swear it runs like a new vehicle.

 

[ZeroData]

I'd say it's time to change your plugs and wires. I had the exact same thing start happening on my 97 with 185K on it (original plugs and wires, I found out later).

Replaced plugs and wires and I'd swear it runs like a new vehicle.

I've already replaced the plugs, wires, tested injectors, moved injectors, ran a noid light test, a spark test, a compression test and tested the coils.

The problem is that there is NO, read 0 PSI, compression on cylinder 4. I pulled the valve cover today and all of the followers are still attached. Tuesday I will be pulling the head to check all of the valves and related parts. The vehicle does not smoke and compression on the other cylinders is acceptable.