Q: When shifting it bogs down then rpm shoots up and bogs down again before returning to normal.

asked by on January 29, 2018

When shifting out especially when coming to a stop my truck bogs down then rpm shoots up, bogs down again, and then returns to normal. I have a 97 Ford F250 four-wheel-drive, aftermarket engine 5.4 L. I have replaced a couple vacuum hoses, EGR valve, EGR tube, two spark plugs cylinder one and cylinder seven, a coil pack on cylinder seven, and repaired a crack on the fuel rail. I can’t figure out what’s wrong.

My car has 230000 miles.
My car has an automatic transmission.

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Is the engine "new" or "re-built"? If it is a used engine, check engine compression. Loss of power on acceleration can be due to plugged fuel injectors, faulty oxygen sensors, fuel pump and/or filter, vacuum leaks including that caused by a faulty EGR system, ignition system malfunctions, bad valve timing if the timing belt or chain is worn or skipped, blocked exhaust (e.g., catalytic converter fails or becomes clogged), a faulty airflow sensor or throttle position sensor, and so forth. To pinpoint the exact cause will require an engine loss of power diagnostic. If you request that diagnostic, the certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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