I picked up my 97 12 valve two weeks ago from a Guy from as far as I can tell did little to no preventative maintenance. Last weekend I put in new brake hoses calipers pads rotors and hubs in the front. In the rear it got new hardware shoes and wheel cylinder. I put in a new fuel filter I stalled a BHAF and added power source diesel fuel additives. Yesterday I put in a bottle of Lucas tranny fix. Today driving it home the rpm's started to fluctuate with about five interior dash lifts coming on at different speeds each time. When I come to a stop the rpm's return to normal. When ever I'm on the gas it fluctuates and sometimes sounds like its gonna die. The speed it attempted to seem like it was shutting off also changed so it wasn't at the same speed each time. It was only a 10-15 minute drive home. I checked the battery connections and they were tight. What can be causing this???

Also on a side note my tranny won't shift into overdrive until exactly 48mph... Is that normal??

 

i would start by checking your crank postion sensor as far as the dash lights coming on at different speeds. clean the sensor and re gap. 48 mph is normal for o/d.

 

the rpm thing sounds almost like a fuel pressure problem but sounds odd. the interior dash thing sounds like an electrical problem. you have some situations on your hands bud.

 

x2 and yeah the o/d is normal my 12v doesn't shift till 45 ish

 

The truck started having the rpm's fluctuating at idle so i popped the hood to play with some wires and see if i could make it better or worse... I noticed something looking off so later when i looked at a Haynes Manual i found out is was the vibration damper. Once the engine was off i noticed the damper also had two huge chunks taken out of the rubber ring around it. And since the crank positioning sensor needs to be .050" off of the damper im guessing since it was wobbling around i think it knocked the sensor out of place so it can't read right. So now i have to decide between a stock damper and the fluidamper which is like 464.

Either way i'll change the damper in a few weeks when i tab my KDP and hopefully do the electric fan install too