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By drewwarntjes, March 16, 2017

I am getting 27 mpgs which seems low, also i feel the engine does not run super smooth idling in park. The other day i noticed it worse after starting car, then idle jumped to 2k rmps and stuck there. Emissions were super rich smelling then i shut off car restarted car and it was back to normal idling. Really weird. Car has 92k miles.

Also, just had oil pressure sending unit replaced due to leak.

Could be just a simple maintenance issue. With that sort of mileage on the car - I would definitely pull and read the plugs - see if they are excessively worn, any combustion issues with any of the cylinder(s). As for the jump in RPMs, that could be related to a clogged PCV valve, dirty throttle body (careful when cleaning, don't want to mess up the servo on the DBW TB unit), and/or vacuum leak. Common on 9th gen Corollas with the composite intake manifold - the silicon gasket between the manifold and the cylinder head could be damaged, causing a huge vacuum leak that usually manifests as uneven idle / idle surging.

Also possible that the AFR sensor is getting lazy or is faulty. Generally they hold up for a fairly long time, but they won't last forever. Some have died with less than 30K miles on them, others have exceeded 150K miles. They have to be backprobed with a scope to verify their signal waveform - but if you noticed that fuel economy took a huge nosedive, this would be higher on my list of possible culprits.

Looking 2007 Corolla S here with 84k miles on the clock. Seems running good but will check the idling status and mpg.

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