The eighth generation of the Mitsubishi Lancer.

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Bad fuel mileage and rough idle

Rough idle with bad fuel consumption?

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Usually when this occurs I would start looking at the spark plugs. Reason being is if your spark plugs are fouled is when this starts to occur. The other things you could look at is a replacement air filter, fuel filter and a oil change. If it has high milage I would suggest the Castrol High Milage for the oil if you can get it. You could also add Bardahl high milage when you do the oil change which would also help with maintaining the engine and cleaning up any gunk and carbon build up.

Good luck

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I just had this issue, in my case my throttle body and Intake Air Control Valve needed cleaning. Plenty of youtube videos to show you how if u dont already know. After i cleaned it i had to adjust the Throttle Cable "stoping screw??".. Then Using a multimeter to read the voltage being sent back to my ecu from my TPS. Currently it sends .50 volts to the ecu when it is at a regular idle and close to 5.00 when throttle is wide open..... With that said it could literally be 30 different things but in my case the carbon build up wasnt allowing the butterfly valve to properly close therefor the tps and iacv were getting wrong readings and got off sync.

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Air, Fuel, Spark

Any of these can cause the issue. I have seen simple air leaks in the EGR system allow too much air and I have seen “home made” cold air intakes where the MAF (Mass air flow) sensor was just moved out of the way.

An engine light will accompany most conditions as well.

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