I am having an idle/rpm problem. I have a 1998 F150 4X4 4.6 V8 Manual transmission.
I am having the rpms hang up longer than normal while driving, shifting, clutch in coming to a stop etc. Sometimes the rpm increases on it's own causing the truck to surge.
I know that when I put in the clutch without using the gas pedal the rpm is supposed to drop, not increase like it does now. Coming to a stop for instance, I will have one foot on the clutch and the other on the brake yet my rpm will either hang up between 1500 to 2000 or climb there, other times it stays relatively normal.
Now for the fun part, this does not seem to happen when I have turned the heat/air control to the off position.
The Idle Air Controller has been replaced because the mechanics swore this had to be the problem but has not had any effect.
Any ideas will help. I'm not a mechanic but this seems to have stumped the mechanics I've asked.
Del.