engine reving up and down during warm up

[twofast4u]

Hey guys,

I cant seem to find this using the search, so im just gonna ask. Every time i start my car after its been sitting for about an hour or 2 or actualy lets just say every morning. The engine stays at 2000rpm. Then after 3 or 4 minutes it starts to rev by itself from about 1500rpm to about 2000 rpm. after about 2 minutes of that it stays at 1100 rpm. Then eventualy it will sit at about 800 or 900 rpm which i think is the normal rpm. Has anyone ever experienced this? If so what was the solution. BTW i just did a carb to EFI swap in august.

Thanks

[shepherd79]

the problem is your fast air valve. you have to choices. you can adjust it or you can get a new one. it is located on the back of throttle body.
to adjust it, remove the two screws that hold the top of it. take the wide flat screw driver. start the car. adjust it untill the fast idle is at 1400-1500 rpm. the fast idle should be stable.

[oldschool3g]

my car has only done that once...its like it was possesed..lol. when is a good time to adjust it? in the morning when the idle is high?..or just whenever i start my car?

[shepherd79]

the best time to adjust it would be when the engine is cold. you are adjusting FAST IDEL VALVE. the valve only works when the engine is cold.

[twofast4u]

sounds good, i'll give it a shot, cause i hate getting looks from people when im parked and its just reviin continuously.

[w261w261]

Well probably your fast idle valve needs adjusting or replacing, but also, if you any air bubbles in your coolant, it will make things behave like you have described. Make sure you have completely bled the cooling system using the bleed valve by the thermostat. Have the engine warm enough to have the thermostat open, and turn the heater all the way to hot (to make sure the coolant is flushing through the heater coil). Open the bleed valve and see if the water that geysers out has any bubbles. Keep it going until no air bubbles are present. Be sure when you're done to clean up the coolant on the ground, because it is sweet and very poisonous, and as little as a teaspoon will kill an animal.