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Q: Car constantly shutdowns when it hits low RPM (idle) in traffic

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Greetings, Last Sunday I decided to clean up the throttle body due to the fact the engine (after a few minutes of having started it) would have a life of its own. It would (without touching the gas pedal) raise itself to a higher RPM (like for a second it can go from 1000 rpm (idle) to around 4000 a 6000 rpm on its own for a very short amount of time). And also it shuts down randomly. Doesn't matter if i'm running or at idle. After cleaning the throttle body, the car now its working like a charm (no random ghostly racing, no random shutdown), but now I have a constant problem. The car constantly shuts down when ( for example when i'm at a red traffic light or even waiting in line at idle). So with other words the moment that I take my foot off the gas pedal and the car goes in the low rpm's, it turns off. It has new spark plugs. I think (maybe) the problem lies at the car's fuel pump. The car doesn't display the "check engine" anymore since the cleaning the throttle body. Any tips pls?

My car has 7456454 miles.
My car has an automatic transmission.

A: Hello. There are several issues which could...

Hello. There are several issues which could cause this behavior. A dirty throttle body (which you have already checked), a dirty idle air control valve, a failed throttle position sensor, an air leak in the intake (loose or split hose, crack in plastic components).

Poor fuel supply or issues with the fuel system can also be a relevant problem (clogged fuel filter, worn fuel pump, bad fuel pressure regulator, dirty fuel injectors). Check fuel pressure to determine if there is a supply issue.

Check for problem codes, even if the Check Engine light is not illuminated there may still be pertinent information or data. If you need help having this all scoped out for you, a certified professional from YourMechanic can come to your car’s location to have the stalling issue diagnosed and repaired.

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