Is it possible to reduce the minimum throttle on a passenger car (auto trans)? Is it advisable?

Question

If my ScanGague is to be trusted, my car's minimum throttle (throttle position at idle) is 9%. I'm wondering if it's possible to make this even lower, and maybe save some gas in the process (e.g. in-city).

I understand though that the engine needs a certain absolute minimum throttle to a) operate and b) move the vehicle, but is that necessarily the same as what the throttle's minimum position is?

paul4001 · Accepted Answer

Most fuel injected cars have their throttle plate closed at idle. It's the IAC that bleeds the air in and thus sets your idle, so you can "tamper" (against the law) with it but the pcm will always make adjustments to try to compensate for your adjustments..... it's computer controlled.........plus I think your basing your opinion on carburated system where the more the plate was open the more fuel was drawn in. Fuel injected cars get their fuel via injectors, so the computer delivers just enough to maintain idle, and keep the catalytic converters at peak operating temperature ensuring your vehicle doesn't emit too much pollutants.

racegene · Answer

The TPS sensor acts on a "range" but the end result is that when the ECM determines that the engine is no longer under load, it will reduce the fueling to the minimum amout needed to maintain idle.  I have seen throttles that do not respond untill 15%.  It all come down to making a cheaper TPS sensor with poor tolerances on design saving 5 cents.

OK Faith · Answer

I'd just go for it and not worry.  I think it's possible and advisable.  Have fun!  :)

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Is it possible to reduce the minimum throttle on a passenger car (auto trans)? Is it advisable?

3 Answers