RPM's on cold start?

[T86951]

On a cold start my RPM's are about 600-700 and rough till it warms up. What does everyone else cars do as far as RPM's on a cold start? Does your car rev up? To what RPM's and for about how long before it slows down to normal idle? Thanks.

[lm6y]

Mine idles at 900, whether it's -20 or +110 degrees outside, and sitting overnight. These cars shouldn't rev up even when cold. The only reason that a carbureted car revs up when cold is because there is no air fuel metering, other than the idle circuit in the carburetor, and a choke plate. Think of it like this, A carburetor is a BARELY controlled fuel leak, where electronic fuel injection is a PRECISE system of air/fuel metering at ANY temp, ANY altitude, EVERY condition, unless a sensor, or a control unit is malfunctioning. Bite the bullet and replace the Idle Air Control unit. If it doesn't solve the problem, that's one more thing to cross off of the list to look for. The idle air control valve shouldn't make it rev up, unless it is malfunctioning, or is getting a wrong signal from the DME. The "choke" on these cars is a combination of Fuel injector pulse width (how long the injector stays open), Timing control, And the Aux. Air valve OR Idle air control unit. When an engine revs up when cold, all it does besides warming up, is increases wear on the moving parts. That's why the cold idle on these cars stays at a lower rpm, and the manual says to not exceed 4500 rpm until the engine is at operating temp., and don't let the engine idle for a prolonged period. Iknow it's a pain, but start the car, let it run for 5 mins to get a little heat built up, and get the oil moving, then drive off. It will warm up sooner this way, than to let it idle for 15 minutes.

[T86951]

Thanks for the help, I think I will repace the idle control valve. I was just hoping to find someone that had the same problem in the past because the valve is under the manifold.

Thanks

[lm6y]

Sorry man, nothing good comes easy! I'm sure you'll get it. I was a little worried when I had to replace my clutch, but after it was over, I realized it wasn't that bad.