Ok, my truck is a 2000 5.4L 4x4 with 146k miles.
It's doing 2 things that are not normal. The first is a shifting problem, it will hold second gear longer than it needs to before it shifts to third. Takes about 5 seconds longer from the time it would normally shift to the time it finds third. It did this before but stopped for a while, now its back.

Second. Now that it has gotten pretty cold I've noticed that any temp below 20 degrees the truck will idle rough. It acts like it wants to die, the rpms will drop between 300 and 600. And it only does this after I've driven about 2 miles and the engine is starting to warm up.

Im thinking its got to be a sensor. I'm thinking either the IAC valve or the throttle position sensor.
I would just replace both but money is tight with Christmas and the fact I just bought tires.

Any help would be HIGHLY appriciated!

 

I bet its ur IAC!

 

How hard is it to change? I'm pretty handy with a wrench, just don't know a whole lot about the 5.4s

 

IAC. We had a guy on here 2 days ago with the same exact thing. His was doing your sypmtoms exactly.

The other might be a bad VSS in the tail of the transmission. They tend to cause bad shift patterns as well as dirty transmission filters.

 

Simple two bolts and one connector. Takes 5 minutes to change out.

 

Thanks man, I'm gonna swap it out tmrw and hope it fixes it. If it doesn't, how hard is it to change out the TPS and the VSS?

 

All the items you are asking about are relatively easy to do on this truck. TPS would give you a stutter or flat spot when starting off, so doubtful it is that. The speed sensor is on the tail of the trans (4x at least) and has a wire harness going to it. They have problems in cold weather and tend to cause long, erratic shifts and hard down shifts and even free wheeling. That may be a trickier removal, but with the right tools, not a problem to change out. Good luck.

 

Thanks again man!

 

I'd say IAC valve as well, i just had to replace mine at 140k. Truck ran great all summer and most of fall but once it got a little colder it began a rough idle which basically lead to stalling out every morning unless i gave it a little gas for a minute or so

 

Thanks guys