Where to look next?
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Where to look next?
I have an 89 F-250, 351W, 5 speed. The problem I'm having is sluggishness and "missing" (truck shudders and loses power and speed) when trying to accelerate at lower rpms (under 2.5k) while at highway speeds. If I'm at higher rpms, or at lower speeds (1st and 2nd gear) I don't have a problem. The truck is also idling rough when cold.
Here's what I've done so far:
New coil, plug wires, cap and rotor, ignition control module, and plugs (autolite copper)
Verified plug gap (all at spec.), and timing (stays steady at 10 degrees)
New fuel filter and fuel pressure regulator.
Checked all the hard vacuum lines for leaks, replaced the ones that were bad.
Checked for intake leaks, none detected.
Removed the idle air control valve and cleaned it using Sea Foam
Sea Foam'ed the snot out of the intake, running a pour-in bottle through the tank, then ran her out on the highway for a while to help blow out any carbon.
Verified fuel pressure, steady 42lb. at the test port.
Not getting any codes.
Okay, not sure where to go from here, I don't hear anything like a sticking valve, but I suppose that I could have a lifter going bad. I've considered replacing the idle air control valve, would that have anything to do with it? Getting a little tired of just throwing parts at it, any suggestions would be appreciated.
Here's what I've done so far:
New coil, plug wires, cap and rotor, ignition control module, and plugs (autolite copper)
Verified plug gap (all at spec.), and timing (stays steady at 10 degrees)
New fuel filter and fuel pressure regulator.
Checked all the hard vacuum lines for leaks, replaced the ones that were bad.
Checked for intake leaks, none detected.
Removed the idle air control valve and cleaned it using Sea Foam
Sea Foam'ed the snot out of the intake, running a pour-in bottle through the tank, then ran her out on the highway for a while to help blow out any carbon.
Verified fuel pressure, steady 42lb. at the test port.
Not getting any codes.
Okay, not sure where to go from here, I don't hear anything like a sticking valve, but I suppose that I could have a lifter going bad. I've considered replacing the idle air control valve, would that have anything to do with it? Getting a little tired of just throwing parts at it, any suggestions would be appreciated.
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