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Fast Idle at cold start up

Have a Toyota Tocoma 2.4 engine that idles 2000 rpms on ocassional cold startup. This idle speed is far above the normal cold startup speed. Also idle speed does not decrease ans engine warms. Must be shut down and restarted. Then engine usually idles at normal. Check engine light was on had checked was a O 2 sensor on exhaust prior to convertor. Light went out on its on after about 50 miles driving. Any help with the idling problem ?

How old is it? It could be a lazy IAC. Sludge and gunk buildup inside the throttle body, especially the IAC port can contribute.

Also, the problem with the O2 sensor can be lots of things. There are several codes that refer to this single O2 sensor. Having the exact code, like P0XXX will help allot to figure that out.

The throttle plate may be sticking, intermittently. What could help either problem, gunky iac (idle air control) valve, and throttle plate/bore, is a thorough cleaning with Throttle Body Cleaner.
It might help, with what caused the the O2 sensor code, if you cleaned the MAF (Mass Air Flow) sensor with MAF Cleaner, while you have the intake tube off.

Thanks for your help, I had the throttle body assembley thoroughly cleaned (they used a top engine cleaning kit) Also I had the fuel injectors pressure cleaned. Truck is 2001 and runs great with 143,000 miles but still very concerned about the fast idle on cold startups. Cleared code P0420 from ECU which showed that the cat, convertor efficiency is low. Can low reading on cat. convertor cause high idle or faulty reading of the O2 sensor? I had replaced the MAF sensor abour a year ago.

Fast idle is still a problem. 35 degrees outside and when 2001, 2.4 Tocoma was started it idles extremely high. Engine would not idle down after extended warm up, had to restart the engine three times before normal idle speed was obtained. Check engine light has not come back on. Please refer to all prior post for complete details about this issue. Any help appreciated ?

a top engine cleaning kit won’t clean up the IAC valve or its ports the way you can by pulling it off and doing it by hand and visual inspection. If it were me - I would do that next. same with the throttle body plate

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where is the IAC valve and ports located ? Also the throttle body plate? I know across the top of the engine there is a large tube coming across from the air filter to where the accelerator cable is connected. I not to keen on these issues. But I have recently installed brake calipers and a rebuilt alternator on this vehicle, so I concider myself with some degree of mechanical wisdom. What do I need to do to"pull it off and inspect" as you mentioned in your post? Does it require any specific tools, gages etc… Thanks so much for any help !!!

i’ve never looked at one of these motors, so I can’t give specific visual reference, but the IAC is also called a “throttle by-pass” and should be mounted on the throttle body somehow right at the end of the air intake tube where it connects to the throttle body - i.e. follow that long tube away from the air filter to its other end where it connects to the engine. what it is connected to should be the throttle body and the IAC should be right around there somewhere and should look something like this:

it is unlikely to require any kind of special tools. all i would have handy is a can or 2 of intake cleaner and a new gasket set for the throttle body & IAC.

since you’ve gone as far as something like caliper & alternator rebuilds i think you should go out & pick up a haynes or chilton’s manual for this truck - it will show you where everything is and how to mess with it. $20 or so and well worth it if you have a tendency to get your own hands dirty.

Thanks, a friend and I will move the vehicle into his shop, due to bad weather, sometime in the next few days and clean the throttle plate and IAC valve as you stated. Will post results when completed. Your reference above appears to be a starter part. The Idle Air Control on the same web site looks different. Will definitely be looking for the manual you mentioned