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Q: Rom is running high in my truck

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i replaced my head gasket in my truck, after i was done, my rpm runs extremely high now and i replaced my air control valve. So i know its not that. i checked all my hoses and made sure they was right and none was unhooked and i didn't find any and i looked multiple times. I also checked my throttle body and that is fine. Does anyone have any idea what it could be? my rpm goes up to 5,000 when its idling. thank you

My car has 580000 miles.
My car has a manual transmission.

Hello. This is a sign of a vacuum leak. A vacuum leak can be one of the most frustrating and difficult problems to diagnose. Idle speed that is way too fast is one of the common signs and stalling is another. Confirmation of an engine vacuum leak can be a very loud hissing sound coming from the engine area.

Hesitation can come from accelerator problems but it also may be symptomatic of an engine vacuum leak. A vacuum leak is a problem that creates consequences that will include both poor fuel efficiency and a loss of power in the vehicle. The air-to-fuel ratio is a critical factor in the proper operation of an engine. The proper amount of air has to be present in order to maintain proper firing sequence and running conditions. The leak can result in an imbalance in the air/fuel mixture that is injected into the engine. When this happens, this can cause the engine to stall or the RPM’s to rise abnormally. I would suggest having a professional, such as one from YourMechanic, come to your location to diagnose the high idling issue and proceed with proper repairs.

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