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, po171, po174 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. Also, there is a sulfur smell after the rough idling occurs (catalytic converter?).

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.

 

90% of cylinder code failures are due to the COP (ciol) , not the spark plug. I think i would change the COP next time you get a cylinder ( 303, 308) code. You know the numbering sequence starts on the passenger side, front to rear ?
I think you said your not using antifreeze ? Level in the overflow tank is the same week after week ?
Excess oil consumption is often related to a failed PCV valve, or new valve of the wrong style.

 

The plugs needed changed anyhow. The plug in cylinder 3 was different than the others, and the other 7 were rusty and very very worn.

I will go get a new PCV valve then and make sure it is the correct one.

No coolant is being used, the overflow level has not changed at all.

Is there any way to test a COP? Would it short out/malfunction sporadically, or would it be a consistent thing? I'll look into getting a new set.

 

The white exhaust is very often coolant getting into a cylinder.
Good to put plugs and or coils in so it can clear some of the issue away to see what's left.
If you still have misssfire codes that can't be explained, a good Scanner to look at mode 6, test ID 53 for stored missfire counts on each cylinder will tell you the rest of the story
A head gasket change may even be needed to address the white exhaust vapor.
Don't drive the truck with missing cylinders.
The Cats may have taken a beating as it is.
Good luck.

 

I just recently bought a 1999 F250 light duty with the 5.4L. Just the other day it was running great and suddenly it feels under powered and idles rough...now l, noticed white exhaust...any ideas?