Warm up idle speed
 

When I first start my 92 F150 in the mornings, the idle speed changes. It will start really slow, about 800RPM, then surge to about 1600RPM, then back to 800 then back up. It will do this until I finally start to drive it. When it is warm, it idles just fine, this only happens when it is cold (engine, not outside temp). Should I be concered about this? Is there a problems I should have checked out? BTW, it is a 5.0 engine and has about 93000 miles on it.

Probably a dirty Idle Air Bypass valve (located on the right side of the TB). Disconnect your battery, then disconnect the IAB plug and remove the 2 bolts holding it to the throttle body, then remove the 2 little screws that connect the valve. Using carb cleaner, soak the inside of it and clean off the rod so it moves freely, then air dry and reconnect everything...but first, use that carb cleaner spray (and a lot of it) on the TB and wipe it off, especially around the flap. Finally, reconnect the battery. This should help your idle straighten out. I do this as regular maintainance every spring and fall, along with a can of Ford fuel injector cleaner, and have never had a idle problem in 94,000 miles on my '90 LX 5.0. I hope it works for you.

Probably a dirty Idle Air Bypass valve (located on the right side of the TB). Disconnect your battery, then disconnect the IAB plug and remove the 2 bolts holding it to the throttle body, then remove the 2 little screws that connect the valve. Using carb cleaner, soak the inside of it and clean off the rod so it moves freely, then air dry and reconnect everything...but first, use that carb cleaner spray (and a lot of it) on the TB and wipe it off, especially around the flap. Finally, reconnect the battery. This should help your idle straighten out. I do this as regular maintainance every spring and fall, along with a can of Ford fuel injector cleaner, and have never had a idle problem in 94,000 miles on my '90 LX 5.0. I hope it works for you.

Probably a dirty Idle Air Bypass valve (located on the right side of the TB). Disconnect your battery, then disconnect the IAB plug and remove the 2 bolts holding it to the throttle body, then remove the 2 little screws that connect the valve. Using carb cleaner, soak the inside of it and clean off the rod so it moves freely, then air dry and reconnect everything...but first, use that carb cleaner spray (and a lot of it) on the TB and wipe it off, especially around the flap. Finally, reconnect the battery. This should help your idle straighten out. I do this as regular maintainance every spring and fall, along with a can of Ford fuel injector cleaner, and have never had a idle problem in 94,000 miles on my '90 LX 5.0. I hope it works for you.