coolguytex

I just drove my car to get some food and I realized that it was idling at around 750 however it was going up and down from 750. Also there is a vibration through the car while its idling. I'm just wondering what I should check. As well as two days ago it threw a P0440 code at me so I removed and put back the gas cap and removed the negative cable from the battery for about a minute and I haven't seen the code since. Any advice would be greatly appreciated.

thomas1

Search Idle Air control valve cleaning on this site. here it is:
https://www.clublexus.com/forums/rx-...-write-up.html

hsmac

what's your vehicle's mileage? since you're asking, you probably need to clean the iacv as the rest of us had. i had the same symptoms last year.

hsmac

i read that spark plugs are a culprit when a car runs rough. can anyone explain what "running rough" means? i presume my car runs and fires smoothly but maybe it doesn't. i changed my front plugs this year but not the rears.

salimshah

running rough (engine): Means that the ideating speed is not steady .. it can be hunting or misfiring. Misfires are typically detected by the ECU and you get a CEL. As plugs wear down you may get most of the time good spark and once in a while a weak spark.

Salim

thomas1

Your varying idle speed and vibration sounds like IACV needs cleaning and the rattle noise may be the Flex pipe (exhaust) under the engine.