99 throttle instability at low RPM
Hi all:
My 99 4.0 V6 has started having issues at low RPMs where the throttle will oscillate. This is especially noticeable immediately after starting, where the RPM will drop to below 500 and nearly stall, then surge up to around 1200, and fall back to almost stalling a couple times before stabilizing just under 1000.
This is especially noticeable when driving at low speeds and the RPM around or somewhat under 2000, where it will act as if someone is stepping on and then releasing the gas pedal.
Recently its also had a hard time starting, acting as if its not getting enough gas. I have recently replaced the fuel pump. This problem does not change much with engine warming, and at highway speeds the vehicle drives fine.
Any suggestions as to where to look? I'm not that much of a mechanic yet, but I did look up info on the TPS, and it doesn't sound like the descriptions others' gave of TPS issues, but perhaps I'm wrong...
Anyway, I'd appreciate any further input! Most of everything on the truck is still original, about 73,000 miles.
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