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The mkiv Supra Owners Club

Low idle - advice please


viper

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Iv finally got the car sorted but since having the new r154 box and lightened flywheel the idle is low and every now and then when changing down to first from second the engine will stall. I'm guessing its because the idle is low. Could this be something to do with the lightened flywheel? There's no boost or air leaks. I know there's no idle adjustment screw and all I can find about idle adjustment is adjusting the throttle cable directly which doesn't seem right. Any advice would be much appreciated.

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A very light flywheel will often make for an unsteady idle, but not a low idle speed. NA's are a PITA when they get old, and often suffer a low idle. The idle speed control valves gum up, go electrically faulty, and can cause this. as can worn or incorrectly set TPS sensors. Air leaks may cause it. The first thing to do is get a garage to put a `scope on the IAC valve inputs at the valve and see if the ecu is trying to control it properly (15 minute job). If it is, and the TPS sensor and throttle positions are set *PRECISELY* as per the factory manual, you can probably safely assume it needs a new IAC valve assembly. They are costly! Cleaning rarely works for long, they just seem to get tired, or a coil in them fails and goes open circuit.

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Iv just stuck on a toms ecu but i noticed the idle issue before. I not sure about a low redline although I did think it hit it quickly when I revved it yesterday stationary with the stock ecu. It's an Na with a TT conversion that came off an auto. Now with an r154, lightens flywheel stage 5 clutch, bpu. It drives fine just now and again as I drop from second to third it cuts out.

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