Digger

I have a 91 f-150 with the 4.9 and it runs fine when cold but after its driven for a little bit and gets to operating temp, it skips at idle. Its not a constant skip, happens here and there but only when warm. The engine light comes on and goes off. I scanned the codes and it came back as the TPS and EGR valve. I replaced both and the problem didnt go away. Any ideas?

Digger

no one?

boggin_bronco95

I would look at the TFI. it tends to act like that when it's going bad. It's the part on the distributor that all the wires go into. heat is hard on them. that's why they moved them to the fender in 92

Digger

Im not much of a mechanic to bare with me Do you have a picture of what this looks like?

boggin_bronco95

Here is a picture for ya. It's the rectangular module attached to the distributor. I circled it in red. Takes a small torx bit to remove, can't remember the size. I would get a junkyard one just in case it isn't the issue but from what I have experienced I would say it's bad

Digger

Thanks! I looked on my truck and its not there. I ran the VIN # and see thats its a 1992, not a 91 like I thought. Im guessing they changed the location of this in 92?

boggin_bronco95

Left side (drivers side) wall above the wheel arch. It's in a heat sink.

Make sure you clean off the heat sink to BRIGHT metal (400 grit Wet-dry works real well) where the TFI module attaches and use NEW Heat sink compound.


That's the new location of the starting in '92. Normally in that year though the TFI isn't the issue but it's worth checking out.

Digger

Thanks, I will try that! If thats not it, what else can I check?

boggin_bronco95

The only other thing I can think of is maybe when the engine is warm it opens up a vacuum leak but that would mainly cuz it to idle like crap.