Explorer P0304 Code - Cylinder #4 Misfire

cylinder
code
misfire

#1

My 1997 Ford Explorer SUV has 193K miles. Check engine light indicates P0304 code. A garage and the Ford dealer cannot detrmine cause. Cylinder compression OK. not using oil. Plugs and wires replaced, fuel system flushed, fuel injector for #4 cylinder replaced. Still runs rough (misfire) especially rough at idle, hot and cold, loss of power and check engine light with P0304 code. Ford dealer wants to replace with rebuilt engine. Any less expensive ideas?


#2

If the dealer wants to replace your engine with a new one…they should be able to tell you whats wrong with the old one first! Try another garage maybe.


#3

First of all, you need to define “cylinder compression OK”. What is the actual number in PSI? Any ticking noises while the engine is running?
Many times compression readings are stated to be “fine” when they are not.

If the cylinder compression is legitimately ok then why in the world would they recommend a rebuilt engine?


#4

One thing I noticed that had not been checked is the status of the valve lift of the valves of #4. If one of the cam lobes is not lifting the valve correctly, the cylinder dynamics would be off. This might not be noticeable in the compression check. At least checking this would cost only a valve cover gasket and a little time.

Hope that helps.


#5

There’s no where near enough information here to surmise a guess, but I can tell you that what’s here does not indicate a need for a new engine. Either there’s a whole lot of info missing or you need a new shop.

What’s been left out?


#6

This may or may not be similar, but the four cylinder engines in Ford Escorts had a nasty problem that started with #4 cylinder misfiring. Eventually the valve seat would drop out of the head and into the combustion chamber that that was all there was. The problem started with overheating. Check the spark plugs and look for signs that the cylinder is running hot. If caught early on the Escorts, a rebuilt head was the fix; far less expensive than an engine. Again, I don’t know if the engine in your vehicle has this problem, but it is a Ford, it is #4 cylinder and it is misfiring. I suggest you take it to another repair shop; a new engine seems extreme.


#7

Same as my thoughts. I’ve actually heard now many stories about V6 Explorers with cylinder 4 misfire that Ford Dealers have not been able to diagnose. One begins to wonder about built in obsolescence. Shouldn’t Ford at least know what things to check?