High idle 89 c2500..5.7 TBI... starts normal idles fine, then sputters a bit and kicks into a high idle and wont stop.. i recently replaced the following-- Fuel pump,fuel filter, TPS, coolant temp sensor,ignition control module, idle air control valve, ignition coil, cap, rotor, wires, plugs, starter, fuel injectors...sometimes it wont idle high and i can drive it for an hour or so with no problem..then out of no where it'll start idling high.. im confused ..if anyone has any suggestions please HELP

With high idle in park, usually my first test is to block off mouth of throttle body. It should kill the engine, if no or very little effect on idle, You got false air getting in there from somewhere.
What about your cruise control? You can check and clean idle air system, where applicable? Any applicable trouble codes?
I don't know year--make--model?

check fuel pump pressure- fuel filter --air filter --egr valve if carboned up clean or replace and cat converter feel the exhaust if feels restricted may be clogging up

vacuum lines

ing. mod. and coil pack may be starting to go bad had same trouble with mine only a tune-up problem solved then came back be fore i put car on di machine found that coil pack was bad! when if you scange coil pack or ing. mod. replace all, if not will have problems again.

check and clean EGR Valve using a non-chlronated brake cleaner

Could be a vacuum leak as it falls off under acceleration and does not play a part then. Check for broken or cracked hoses.....

i would first check the idle position sensor,located where the throttle cable ends at the tbi. check for broken wires or hoses, try un-plugging and see if the problem goes away. get back to me if you need more help. please rate my fix. Thanks Ray

try replacing the fuel cervo, tripping of rpms mostly comes from faulty cervo. hope this helps

Hello,
The car may be hard to start because it may need a normal tune-up. If the spark plugs are pretty used, they will slowly stop burning as much fuel because the spark slowly gets lesser and lesser. On a cold day the fuel is harder to ignite with a small amount of spark.
Normal idle when its cold means that your cars idle is probably too high. If you lower the idle, the choke on a cold day will keep the idle a little higher until the motor warms and then it will kick back off. If the idle is too high, it will run very rich, smothering itself with fuel, and causing the idle to stay low. When the car warms, its creating better spark when its warm, and with the idle being too high its running at a fast idle.
The car wont start sometimes can be the cause of a few things. If the ground is bad on the fuel pump, it wont make a good connection sometimes for when you turn the key on, the fuel pump dont pump the fuel to the engine. Another one can be that your accessory switch can be loose going to the fuel pump. I think its your ground though. Good luck! Hope this helps.
Have a nice day. -Steve

try unplugging the brake booster vacumm line and cap the line to see if this helps.make sure the throttle is against the stop where it hits the set screw for the idle,but dont try to adjust it,its at a factory setting.