bluekim7

I have a 2003 f150 with a 5.4 and about 142,000 miles on it. I have been having a misfire code on Cylinder 4 (PO304) for about 8 months now. I have replaced the COP, spark plug, and fuel injector.

The problem is, when i first start the truck I get a rough idle for about a minute. Then it clears out and runs great. It will do this if the truck sits and engine cools down but doesn't idle rough when the engine is warm. It started this past winter when it was cold outside (below freezing) and has progressively gotten worse and does it every morning now in Michigan.

I am wondering if it is a bad head gasket?

There is no coolant in my oil, never overheats, no power loss, cannot tell of any smoking, and I have not seen any leaks. I am using some coolant, maybe a gallon or two this year. I do hear a girgling noise from under my dash, but that is about it beside the rough idle when the truck is cold.

Any help would be appreciated.

bluekim7

update,
now my truck has been running good, check engine light turned off a couple days ago.

Can a head gasket be bad and my truck run better like it has been for the past week?

When i turn my truck off i can hear a humming noise coming from my coolantg overflow and looks like there is a small amount of coolant coming out of the cap on my overflow.

Any ideas?

radarrunner1

Sounds like you have injectors leaking after you stop the engine. You get an overload condition with the next start cycle until the fuel clears. You may want to check your pressure cap...clean or replace to see if it helps. As far as a leaking head gasket, you could possibly get a "sweet" smell out your tailpipe if you burn antifreeze. Hopes this helps...