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Q: Truck suddenly has no power, won't rev above 4K, and idles fine.

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My truck suddenly has no power - top speed maybe 65 mph, slows to 45 or 50 up moderate hills even if I downshift. It idles ok and at low throttle positions and RPM seems normal but still underpowered. Above 3500 rpm it has a rattle, and seems to miss and buck a bit - had the check engine light flashing uphill. Won't rev over 4K with any load at all. Took it in and the shop had it 2 weeks, couldnt find anything for sure but said they thought the exhaust was plugged. Exhaust seems to blow out fine, but could the cats be plugged? Something in the valvetrain bent or broken? Don't think it's fuel delivery as it would still be smooth. Thoughts?

My car has 160000 miles.
My car has a manual transmission.

Hello there, many faults will cause a lack of power on your 2003 Ford F-150. The most common would be a failed catalytic converter, throttle body plate malfunction, vacuum leak, throttle linkage, fuel pump, or a shift solenoid. When the Check Engine Light flashes this is an indication that something may be damaging the catalytic converter. To avoid any unnecessary repairs, a qualified technician, such as one from YourMechanic, will be able to diagnose your loss of power on site at your own location.

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