When I drive around in the heat of the day (90+) with the air on my idle goes down to barely and I have to hold the go pedal down a bit at every light or the PCM turns off the air conditioning compressor as it's supposed to when the engine is barely turning. Since I can't get a wrench on the idle screw jamnut I set the idle up with the adjustable throttle link (I'm not proud), but does anyone have any thoughts as to why my engine might be doing this? If I turn off the air it does not change the idle.

 

The pump may be getting tired. I take it that the truck idles at a normal speed when the engine is cold?

 

It idles fine when it's not hot. Could it be the list pump? I am replacing it soon anyway....

 

I doubt it. No harm in replacing it, though. Do the old "double dose of additives, work the snot out of it, and cross your fingers" routine, too.

 

I was thinking the same thing.

 

It's been too many tanks since I put additive in. Wallyworld has been sold out...
Low sulphur fuel seems to help a bit.

 

I set my idle up (too high) and noticed that I have a rattle in the engine until the oil pressure comes up. It sounds like valve train, but I'm not sure.

Crud!