I have an 04 FX4 5.4 and it is missing. I had all the spark plugs replaced and the coils, also replaced the online fuel filter. Runs fine for a short time then goes into limp mode. The check engine light comes on and the computer analyzer shows a code indicating the temp sensor in the head shows 240 degrees almost immediately but it is not over heating. Changed the sensor anyway. Took off the intake manifold to do replace the sensor. The analyzer also indicates right bank rich and left bank lean. The mechanic said it could be a clogged catalytic converter but the temp gauge used by the mechanic didn't show much heat on the converter at all. The labor bill is mounting and I'm about to pull my hair out and still don't have a repaired truck. HELP!!!!!!!!

 

Make sure the cooling system is full.

 

What coils did you use?

Did you have lean codes prior to removing the intake?

 

Motorcraft coils and plugs. Lean codes came before and after removing the intake.
I had changes the plugs and coils, then went for a drive and it started missing but no check engine light at this point. Went back to garage, checked plugs and coils nothing wrong. Started the truck and took a ride of about 4 miles and it started missing again. The analyzer showed a code and heat gauge jumped to 240 but it was not running hot. It just drops back to limp mode. Cats have been checked for to much heat and they're about 200. I am at a loss.

 

Ok, driving down the road highway speed 65. Engine starts missing. I slow down to 55 and drive another 2 miles, heat gauge which is always less than 1/2 way inches over to 3/4 then beeping, engine starts missing and heat gauge pegs hot. I put the truck in neutral, turn off the key restart the engine, heat gauge goes back to below half way and engine runs fine for a while. I had the cylinder head temp sensor replaced yesterday and it's doing the same thing!!!!!!!

 

Have the coolant tested for hydrocarbons to determine if there is a head gasket leak.

 

X2....Hydrocarbon test should answer your questions.. Sounds like a blown head gasket.
With a blown headgasket you will get a pocket of super heated gas into the cooling system from one or more combustion chambers.
This bubble of hot gases with circulate throughout your cooling system and when it reaches the coolant temp sensor your gauge will spike
only to go back to normal as the bubble passes and moves on. The miss could be caused by coolant entering the combustion chamber and
fouling a sparkplug but the limp home mode my be triggered as well from this condition.
Also this condition will not always show white smoke out the tailpipe it just depends on how severe the gasket leak is.
In any event the head gasket/gaskets will have to be changed if hydrocarbons are discovered in your coolant. Good luck.

 

Where would I get the coolant tested for hydro carbons? Wouldn't the coolant level decrease if it was seeping into the head? It has remained the same. Do you have any idea of why I can move the tranny into neutral, shut off the engine and immediately restart and the temp gauge goes back to normal?

 

Some newer cars will false show the dummy gauge as over heating when the radiator is clogged, or if it doesn't see enough temperature change across the radiator.

 

The problem with the missing is solved. I'll share this in the hopes it may help someone else. The truck as stated would start missing once warmed up and at highway speeds. It would miss so bad you would have no choice but to slow down. Well I found out from a mechanic that the 5.4 engine has a Cylinder Head Temperature sensor and when it read to hat it would throw a code p1289. So I replaced the sensor and still had the same problem! I had the mechanic take the truck for a test drive with the analyzer and he left the truck running when he came back. We lifted the hood and were standing there and he shut the engine off and the fan kept spinning like crazy! There in lies the problem, fan clutch was bad causing the sensor to read a code. Turns out the 5.4 when it gets to hot will shut the fuel off to a couple of cylinders and the engine just pumps air in an effort to cool it. So after 4 days of looking and replacing parts it was simply the fan clutch!!! And the good part is I still have hair!!!!

 

I told you to look at the cooling system

Glad you got it fixed

 

Thanks for letting us know what the problem was. It was very educational!