High Idle on start ups.

[shosvtsc]

Each and every time I start my car (98 SVT) it quickly idles up to about 3,000 RPMs right away. Then after about 4 seconds it drops down to almost 400-500 RPMs then idles back up to about 1500 and sits there. :shrug:. I've done some reading on here and it kinda seems like I may need a new IAC Valve? I've cleaned the MAF and Throtle body, but that didn't really help. Is there anything else I can do?

 

[BrApple]

having a high idle for a short time on startup isn't uncommon.

check for vacuum leaks. pending there are none try cleaning the iac. if that work think about replacing it as cleaning only make it work for so long.

 

[shosvtsc]

thanks for the help I will give it a try.

 

[Big Jim]

If the adaptive strategy has learned bad habits, it may help to reset it.

Start by cleaning the throttle body and IAC.

Then warm up the engine to normal operating temperature.

Disconnect the battery or remove fuses 4 & 11 (98 and older, I don't know which ones for 99 and newer). Leave disconnected for about five minutes. This dumps the adaptive strategy memory.

Now that adaptive strategy has been dumped and it will not be effected by a throttle plate that doesn't close fully due to being dirty, you can start the adaptive strategy toward good habits.

Reinstall fuses or reconnect battery. Turn off lights, AC, heater, readio, etc.

Start engine and immediately bring and hold the engine speed at about 2500 RPM for about 30 seconds. 60 seconds is OK but be consistent with the rest of the protocol. Allow engine to return to normal idle and hold it there for the same time as you held the engine speed up.

Turn on the A/C and raise the engine speed to 2500 RPM for the same length of time, then allow to idle for the same length of time.

Immediately drive car. Drive very mildly for about five minutes.

Now the adaptive strategy should be started toward good habits.