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What is the purpose of isc valve on front of the intake. does it only function when the car is idleing. if it doesn`t close when rpms go up would it affect the performance of the car. I`ve done every thing humanly possible to make the car go. use to rev up to 2500 and go back down. now it won`t even rev up to 1200 rpms and then dies. any suggestions please.

thanks

BDJH

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please Help

What is the purpose of isc valve on front of the intake. does it only function when the car is idleing. if it doesn`t close when rpms go up would it affect the performance of the car. I`ve done every thing humanly possible to make the car go. use to rev up to 2500 and go back down. now it won`t even rev up to 1200 rpms and then dies. any suggestions please.

A quote from the tech manual:

"At low temperatures the ISC valve opens and the air flows through the ISC valve, as well as the throttle body, into the air intake chamber. During engine warming up, even if the throttle valve is completely closed, air flows to the air intake chamber, thereby increasing the idle speed (first idle operation)."

Not closing would simply increase the air mixture so it would run lean. Higher RPMs would be smoother than low then, I believe. Otherwise you could just disconnect the hose and cover the inlet to verify if that solves your issue. Hopefully its not the ISC, as they are very expensive to replace!

If its revving to 1200 and dying, that sounds alot like a MAF problem. Try disconnecting the MAF sensor while it is running to see if it changes anything. If it stays the same your MAF is at fault. Some would clean it, others just replace- which can be a safer option. Local junkyards can get them for cheaper than new. ($100 instead of $600+)

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I had a problem with my car's rpm's surging after the car had warmed up. It also would not idle below 1900 rpm's which makes problems when driving on snow and ice. My rear wheels would spin when I was stopped or trying to stop on slick spots. Not to mention I got terrible gas mileage while driving through town. I was forces to ride my brake everywhere and if I didn't my car would accelerate to nearly 45 mph without even touching the gas pedal. I took it to Lexus and the valve alone was $679. I did learn though that even if the ISC valve was completely disconnected you car would not die or have problems revving up your rpm's like you have stated. I agree with micadevcon and would look to the MAF before I try changing the ISC valve.

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I appreciate the help guys. That is all I wanted to know about the isc valve. This was a big help. I did buy another maf meter. but i`m also thinking it may be bad to. I checked the valve according to manuel by adding 12 volts to make the motor of valve and it would not move in or out or at all.

Thanks

bdjh

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