Engine/Transmission (1998.5 - 2002) Strange lunging problem

[wduffy]

I have a 2002 3500 with the strangest problem. I posted about issues with the cruise control in the past but i'm finding my problem getting worse and more strange.



The symptoms are:



- tach will jerk up and down about 50 rpm

- spedo will jerk up and down in synch with the tach

- all this happened in the past only with cruise control engaged and running above 60 mph where you could see the problem well

- currently engine feels weak when pulling load (searay 22 ft boat, older and heavier)

- when driving with no load using no cruise control i'm seeing the tach and speedo jumping around while holding the throttle steady.

- when pulling loads, i can feel a lunging that is matched to the same wiggle i see in the tack / speedo

- has the fass fuel system on it, steady as a rock at 14 psi at VP44 fuel inlet

- has had the vp44 replaced less than 2000 miles ago under warranty with a rebuilt pump

- carter lift pump was failing but shop would not replace as it showed 10 psi at idle. when pulling hard up hills, it would drop all the way down to roughly 2 to 2. 5 psi again, read by pressure gauge at the vp44 fuel inlet.

- replacement of the vp44 did not cure the lunging of the tach / speedo

- brakes constantly feel like antilock brake mechanish is engaging. What i mean by that is when you push the peddle, the brakes dont' come right on, there is a resistance to motion that has a jumpy feel like the peddle is pushing back at you. If you push hard, you get through it and you feel normal brake action. That resistance thing is hard to describe as i can feel what feels like pressure from the hydraulic pump against my foot that is surging as i push on the peddle.

- i'm not getting any codes out of the ecm when i try to read it with the smarty box.



So no my confusion of how all this works.

- can the sensor on the diff that reads if the rear wheel speed for ABS and for the speedo be giving out bad info?

- would the tach and the speedo get info from the same source? I would think that dodge would read the cam position sensor or something else as the wheel speed sensor is only good while the wheels are actually turning

- what could be causing the weird brake feeling and could it be the same thing that is affecting the cruise control?

- Could i have the VP44 coming apart again?

- Could the ECM be failing (rather weird as i'd heard and seen these things are pretty near indestructible)





I'm very open to any ideas as this lemon like behavior from the truck is kinda annoying for such a nice truck.



if anyone has ideas, i'm also open to talking about it. You can call me if you like 919 757 7458 or email at -- email address removed --.



Thanks much for any help you can give.

 

[csutton7]

you can turn your key on and off(don't start the truck) 3 times and then turn it on---does this in succession---you can then read codes(if they're are any) via the odometer---write them down and get back here and post what you come up----also the camshaft position sensor may be going south, but post the codes and someone will respond... ..... chris

 

[wduffy]

I've got the smarty box with me, i'll try to read the codes that way and see if i get any. I'll also try the other way on the off chance that it isn't reading them correctly.



-bill

 

[wduffy]

only code shown is a 1639. I'm hunting for what would cause that and an explanation for the other problems.



thanks



-bill

 

[Tom W]

If it were only the tach I would suspect the TC locking and unlocking but I don't know how the other problems could be connected. Maybe some strange electrical spikes. I would clean grds and battery terminals and take a good hard look at the batteries.