Fourscoot

At an idle in gear or out of gear my trucks rpm's surge. They increase around 500 rpm for a second, then return to normal. The week before I had a rough idle situation for a couple of days, but that went away for two days then this started happening. Could the two be related and what might the causes be?

Thanx, Scott

Good old Bill

Idle speeds are controlled by the PCM (powertrain control module) thru the device bolted to the throttle body called the ICM (idle control module). Am assuming there has been no CEL (check engine lite) activity. First course of action is to remove and clean the ICM with approved cleaner from parts store. Not knowing your familiararity with this stuff, follow the air intake duct from the air filter to the throttle body. Attached to it is a device that resembles a roll of quarters with an electrical plug at one end and two bolts securing it to the body. Remove and clean the holes or ports.

paul64

I would also look at the IAC (Idle Air Control). My 99 had a similar problem and changing the IAC fixed it. Mine would idle high and then come down. On damp cold mornings I would have to keep my foot on the gas for a minute or two or else it would stall. Sometimes would stall stopping at street lights to. The stalling started only after the IAC really started to get worse.

BroganF150

same here had to replace mine a couple months ago dont clean it out like people say most of the time it doesnt last just replace it its inexpensive and easy to replace