Hello everybody,

My 2003 F150, 5.4L has been having some rough idle/misfires issues both at idle and under load. I have been searching the forums and trying to diagnose it using other members issues with similiar symptoms but I have not been able to find the issue.

I have fixed one big vacuum leak, replaced the PCV valve, new sparkplugs, seafoam and heet in the gas, replaced fuel filter, tested the fuel injector resistance. Coolant levels have not changed. The truck burns about a quart of oil every 1000 miles or so. The white exhaust is heavier than condensation, but it comes and goes. The rough idling comes and goes as well, and it usually happens under load and the CEL flashes.

The codes I get are random cylinders, po303, po308, po316 were the most recent but there have been other cylinders as well. I clear the codes after each attempt to fix it and they come back different.

I notice that there is a small exhaust leak that drips water just behind the engine, and when I shut down the truck a lot of water will pour out of an area just behind the cab on the passenger side as well as out of the bottom of the muffler (small hole, looks drilled).

Usually the rough idle occurs after filling up the tank, but from different stations so I do not think it would be watery gas. I use Heet every fill up as well.

Any Ideas? I'm sure I left out some information somewhere, but I am happy to try any solutions and tell you guys more info and everything.

 

Are you going through any coolant? Almost sounds like your have a head gasket going or a cooling leak somewhere else. Might want to do a pressure check on your cooling system. If that checks out okay, put a can of Bars Leak in the cooling system and see if that helps.