Hi, All.
My problem: my truck (2000 Dak, 3.9L 4x4), is revving HIGH. The only time it sort of doesn't is at flat idle. Otherwise, if I'm running it, it sounds as though it's not shifting on time,screaming down the road. 1st gear sounds like a late shift from 2nd to3rd. I've been told this may likely be due toa bad MAP sensor. However, in my research, it seems tome it could also be a bad TPS. Which is more likely?
Thanks!

 

sounds like a govenor pressure sensor or solenoid is not working right in the tranny... if the tps was an issue, you'd have surging @ hiway speeds as the torque convertor locks & unlocks...

 

before anything, any codes come up? im not certain with your year but you can do the code dance, i beleive it's on,off, on, off, on to the ignition position with the key w/o starting the truck, look for the codes in the milage display and write them down... imo... this sounds like a transmission problem, i would go get her looked at by a reputable transmission rebuilder, not by the stealership

 

yes he can do the key trick to get the codes out... I had a '97 Dak that worked with the key trick.

 

Nope, no codes. Only one I've had is the old P0042. Gonna try a new gas cap.
If it's what you say, what might it be likely to run me?
As an addendum, I did recently replace my rear speed sensor (in the diff). Could this be affecting it?

 

speed sensor would just screw around with your speedometer last i remember...

 

TPS sensor is a simple device called a potentiometer. you can do a pretty accurate test on it with a simple multimeter. pull the TPS sensor from the truck and bring it inside on the table. Set the multimeter to resistance and touch 2 of the pins inside the TPS. i havent had to do this on my dodge yet, there may be multiple pins on the connector but only 2 of them will change resistance when you turn the shaft. the exact values of the resistance arent important. what your looking for is a constant resistance when the shaft isnt moving and a gradual and predictable increase in resistance as the shaft rotates. if you notice the resistance jumping around your TPS is bad and you can be confident about replacing it. as for the MAP theres a resistance test procedure in the book but im not familiar with it. i do beleive that a bad MAP would definately throw a code where as if the TPS was bad the comptuer would just think someone was depressing the throttle. good luck

 

UPDATE

Had the truck in to the shop the other day for a different problem (they couldn't figure it out). They claim to have done nothing to the truck, aside from starting it a couple times a day. When I picked it up, the problem from this thread was GONE!
Shifting like a dream, and so quiet it was like driving a new truck. It was bliss. And then...
After running swimmingly for about a week, on the way to work yesterday I noticed a sudden change in engine tone (going about 55). Sure enough, on slowing down, the horrible roaring was evident again. There was no noise ahead of it, no clunk or bang or anything to signal "here comes a problem". Just happened. NOW--the shifting seems still to be fine. Not running too high before 1-2 shifts, or anything. On further reearch, I 've found a few guys saying that their crazy loud engine noise was actually caused by a bad fan clutch, essentially making the fan follow the engine step for step.
Thoughts?

Thanks,
Chuck

 

I know this loud engine sound that you speak of, my truck does it on takeoff after sitting at idle for a few mins, and then it gradually goes away as you drive. Yours could quite possibly be a bad fan clutch.

 

That's what makes me think it might be the fan clutch. The noise doesn't go away. It's not as noticeable at hgher speeds, UNTIL it downshifts to climb a hill or pass, and then, oh boy. It sounds like an unmuffled v-8.
I may still find thisin another post, but in attempting to turn the fan to check clutchage, shoulod it turn clockwise, or counter Z(looking under the hood from the front)?