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Idle Control Unit

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I don't know if this would relate to the same post as

Engine dies at start up

but let me explain to you my problem.

I have a 1992 ES 300 with about 136K

A Couple of issues with my car has come up and I think they are all related.

1) During ignition (start up) at ramdom times the engine would shake/throttle (what every you want to call it) and the rpm would fall below 500 rpm and the engine would die.

1b) Happens most freqently after driving long periods of time and then stopping for a while (between 30min to an hour) and then starting up again

2) Engine shakes and then dies when exiting freeway offramp when completing a stop. Also at ramdom times.

- It can't be the fuel filter, transmission oil/filter, or the spark plugs since I changed them recently.

- I took it to my mechanic who said that it has something to do with the "Idle Control Unit" that controls my RPM and if I replace it, it would cost about $300 since he claims the part can only come from the Lexus dealer.

- He cleaned something out and now it doesn't happen as often but I do notice that it doesn't seem to have as much pick-up energy as before and that when I drive on freeway speeds (like around 70mph) the RPM barely reaches 3000 RPM when it use to reach 3500 RPM.

My question is 1) what is this "Idle Control Unit" it same as the Idle Air Control Valve (IACV)? Where is it located at and how can I temporary fix it?

2) Will my car break down if I don't replace for the time being and wait until summer when I'll be on summer break from school

3) Is there a place I can get the part for less than $300

4) Should I be concerned with the low RPM for the time being? I don't want to get stranded on a nearly dead freeway on US. 101 since I have to travel a lot.

5) Does the car's computer chip have something to do with this?

Please Help :huh:

Thank you! :)

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i had given someone a list of things to change a few days ago that should be changed anyway for the same problem.

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My wife's 98 ES300 had the same problem at 45,000 miles! This seems to be a pretty typical problem on the ES300 and Toyota cars in general.

I was able to correct the problem by cleaning (internally) the Idle Air Control valve with CRC Air Intake Cleaner. FYI, the IAC Valve is located directly beneath the throttle body. Some dealers clean the valve, while others insist on replacing it (more costly).

A dirty IAC valve affects only the idle and should not pose a problem with highway driving. From a safety standpoint, however, you should get the problem fixed.... you don't want the car stalling when making a left turn with traffic approaching, for example.

Edit - Just noticed that your mechanic already worked on your car, but that you still occasionally have the problem. FWIW, I had to clean the IAC twice before the problem was completely fixed! The Haynes repair manual indicates the RPM increase that should occur when the IAC is activated (temporary jumper on diagnostic plug). The RPM increase was minimal the first time I cleaned the valve, therefore I knew that I wasn't done.

Martin T.

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