SOLVED: Replaced the ICM and it idles perfectly, no lag in throttle input, and no more popping on the decel. Thanks for the input guys.
FYI: My ICM screws were PHILLIPS head! not 7/32 or a torx.
The tach doesn’t “bounce” by itself. It does follow the engine rpm as it stumbles or hesitates, or surges, etc.. I can feel the fluctuation as it appears on the tach.
SOLVED!
I replaced the "VENT VALVE" Dorman #: 911060 on the top of the tank and it fixed my issue! Pressure was not releasing from the tank once fuel level reached connection of the filler neck to the tank.
Ended up replacing the tank as well due to the crud that had built up from the rusting...
Hey guys,
1988 2.9L 5-speed 4x4 super cab
intermittently on idle and when driving the truck has a little stumble (flutter in RPM down). Generally it idles and runs smooth but have noticed more lately stumbling a little bit on the highway and stumbling tach and RPM on startup occasionally...
They are non-greasble but Havent been replaced in 6 years. It started doing it shortly after a pretty gnarly rutted trail I was not expecting and have never flexed it that hard.
Hubs not locked in 2WD there is not vibration or noise and drives great. Hubs locked and in 2WD or 4WD hard vibration and speed up with increasing vehicle speed.
1988 Super Cab FM146 BW1350 manual shift/manual hubs, Extreme vibrations when hubs are locked in 2WD and 4WD... It feels Fine when hubs are not locked in 2WD!
This started during a day of wheeling at the end of the day. Suddenly I had a very noticeable vibration from the t-case shifter and the...
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