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Q: when cranked up it revs up and down

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when you start the truck it revs up and down in till you give it gas or turn high idle on the programmer

My car has 260123 miles.
My car has an automatic transmission.

Hello. This is a common issue in the 7.3 Liter Ford Diesels. There is something called an ICP (Injection Control Pressure) sensor which is located at the front of the motor on the driver’s side near the fuel filter. This regulates the fuel pressure running to the injectors. When this is not working properly, and fuel pressure fluctuates too much, then so do the RPM’s as the motor is getting inconsistent amounts of fuel. I would recommend having an expert from YourMechanic come to your home to diagnose the rough idle and verify which components are faulty.

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