My 92 F150 4x4 5.0 V8 will have a high idle until i shift it into gear, then at the top end of each gear it will just roar and sputter slowing down the vehicle before shifting and accelerate again. When i floor it it just roars and sputters, replaced the fuel filter, the relays for the fuel pump, replaced the distributor, and replaced the spark plugs. Tranny fluid is full and clean, oil is full and clean. Check engine light is not on.
My car has 170000 miles.
My car has an automatic transmission.
Hi there. From the description you have provided, leads me to believe the IAC (idle air control) valve is sticking causing the high idle. The roar and sputters upon acceleration could be a fuel starvation issue caused by, a faulty fuel pressure regulator and/or a faulty fuel pump. A fuel pressure test would confirm this possibility. Another possibility could be, the exhaust system is restricted, ie; a restricted or plugged catalytic converter. I recommend having your vehicle’s cannot get up to speed accelerating be diagnosed and repaired by a certified technician, such as one from YourMechanic.
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