VTX1800N1

I thought about that too. Removed the belt and turned the A/C by hand. Both the pulley and the compressor are smooth as butter. In fact the compressor was easier to turn than I had expected.

Tide89

Without the clutch engaged the compressor should spin completely free. I wonder if you are getting adequate fuel pressure at idle. My last truck (not an f150), one of the first things i noticed when the fuel pump started going out was a rough idle upon startup.
Just a thought.

VTX1800N1

It does.

Unfortunately the F150 doesn't have a Schrader valve to check fuel pressure. I'll have to see if I can get a reading through OBDII

dnlow

This is an idea. I had a misfire on my 2005 5.4L only when the engine was cold that ALWAYS went away when the engine got hot. I searched around here and on line and it seemed like the few things I found were pointing to spark plugs or coils. The issue was is that I had changed both a few weeks back and the engine was fine. Everything worked fine until winter came on and then the misfire started, so I was looking for other answers. The one reason I thought it may be a plug is that I dropped one on the floor when I was putting them in. It took a while but a code showed up and it said I had a misfire on the cylinder that contained the dropped plug so I swapped two coils. I drove it for a few weeks before I got another CEL and it was on the same cylinder so this time I changed the plug and it never has had a rough idle at start up again. It also has smooth out the idle as a whole because over time the misfire at start up got worse and the idle after being warmed up got a bit worse too.

So to make a long story short, I am thinking that one of the plugs may have been handled rough or dropped on the floor.

Again just my experience and another thing that you may want to look at.

Martian

Mine didn't. It was an odd failure. It worked perfectly with the clutch engaged, but disengaged, it created some horrible drag and a terrible whining / wheezing sound. Glad it's been replaced.

VTX1800N1

Fuel pressure isn't the problem here. Pressure at idle is 38.5 - 39.6 consistent. On a drive I got a max of 44.4 and a min of 36.1

I monitored the fuel trims and found something interesting.

Long term fuel trim:
Bank 1 -.8 to 7.0
Bank 2 +.8 to 13.3

Short term fuel trim
Bank 1 -9.4 to 11.7
Bank 2 -10.2 to 7.8

The long term fuel trim for Bank 2 is almost always higher (at times significantly, depending on driving conditions) than Bank 1. Bank 1 stays much closer to 0.

The short term fuel trim for Bank 2 is almost always lower than Bank 1.

This tells me there is a problem with Bank 2, possibly a vacuum leak, injector problem, or O2 sensor. Interestingly, Bank 2 (Cylinder 5) is the bank the dealer replaced a fuel injector under the extended warranty. After the engine warmed up, but before the phaser noise started (indicating no VCT operation yet) it was still idling rough. I put it in Drive and it smoothed out immediately.

VTX1800N1

VTX1800N1

Well, it's not a vacuum leak from what I can tell... I took a bottle of a dilute solution of Simple Green and soaked down the entire top of the engine, specifically the intake gaskets and all vacuum hoses, and the idle never changed in the least. It could be an intake gasket leak in the coolant valley, as I can't really get the spray in there with the engine running.

BONUS: I cleaned the engine rather well....

VTX1800N1

For the last two weeks, the rough idle has been completely gone. We've had hot weather here, so I will have to wait till late Fall before I know for sure that it's fixed. Maybe the computer took a few drive cycles to adapt to the replacement FPDM.

VTX1800N1

Well, it's not the fuel injectors.

The weather turned a little cool the last few days and the rough idle also returned. Today I removed the intake, disassembled both sides of the IMRC and completely cleaned them. The flaps had a thin layer of crud on them but they are nice and shiny now. I also swapped all the injectors left and right. The long term fuel trim for Bank 2 remains stubbornly high, indicating a lean condition which suggests a vacuum leak.







I cleaned the intake gaskets and carefully inspected them. I didn't see any signs of damage. After reinstalling all the parts, it absolutely idles better. It's very smooth, but then again it's hot outside right now.

I think my next move will be to replace the O2 sensors. At 88K miles they should be replaced anyway.