Engine/Transmission (1998.5 - 2002) Tach. Bouncing.......

[onestackdram]

I posted a long while back about my wifes 02 tachometer needle bouncing while sitting in idle both in Park and Drive. Well now it is still bouncing but now it's also doing it while you are driving down the road at any speed in any gear. It will bounce approx. 50-100 rpms. It is a non-stop bounce not hard just constant. Is anyone else out there experencing the same thing?



TIA



Russell

 

[HeavyHauler]

I think all of the needles bounce at idle, but I haven't experienced one bouncing while driving down the road. The bounce at idle really doesn't make sense to me either though, the engine sounds like it's at a constant RPM although the tach displays otherwise.



Hope you get it figured out.

 

[Cobra]

tach problem

your tach is electronic not direct drive so you may have a problem in the instrument cluster. Because it is electronic and not direct drive it can bounce around while driving even though your engine is running smoooth.

 

[RHARVEY]

Take a look at this... . it might help. .



Rick



http://www.autoshop101.com/forms/h36.pdf

 

[Piston Slapper]

Bouncy Tach

Usually associated with Crank Position Sensor. Here is some instructions I found on the TDR. It is located in the side of the block behind the starter. I have this in a Word Doc w/ pics if you want it.



Crank Sensor Install

Tools Needed:

1. 10mm 12 pt socket

2. 10mm 12 pt boxed end wrench

3. 3/8" ratchet

4. 10mm 6 pt socket



Part #:

Mopar : 05015488AA $67

Cummins: 4002066 $37



Instructions:

1. Remove 3 10mm 12pt bolts holding starter onto motor. Two bolts are underneath the starter, one is above. The one above is best removed from underneath the truck and reaching above the starter. Also note that the bolt on the bottom of the starter closest to the outside of the truck is best taken off with the 10mm 12pt boxed end wrench.

There isn't enough room for a ratchet.

2. Pull starter out towards front of truck and let rest on front axle (4x4). Removing the red positive battery cable isn't necessary.

3. The Crank Position sensor is now easily accessed. See figure #3.

4. Remove the one bolt holding it on with 10mm 6 pt socket.

5. Unclip the old sensor and pull out of block. It has an o-ring on it, but it won't drip any oil.

6. Press in new sensor with end of a ratchet. Reconnect the plug.

7. Reinstall the 10mm 6pt bolt.

8. Reinstall the starter and tighten the 3 10mm 12pt bolts.

9. Crank engine and check for leaks.

 

[kstehnacs]

tach bounce

My 02 has done it since day one. I consider it to be a normal condition.

 

[Piston Slapper]

They all do it to some degree. A mild bounce, mine does it about 25 rpms. Erratic bounce would be the CPS. Never seen one do it but have heard many with "bouncy tachs" replace CPs to fix.



I do agreee some bounce is normal at idle. Mine is solid above idle though... .

 

[berg]

my 02 did the same thing it also wouldn't idle down some times after using the cruse for a 100 or 200 miles. Well I pulled off I-80 the other day and had no throttle at all and was idling at 1400 rpm. The dealer where I was at said it was the thottle position sencor changed it and now my tac is steady as a rock. I had also considered its jumping around normal but don't now anyway thats my story and I am sticking to it

 

[JCockrell]

"roo" tach

I recently lost the sensor in rear axle (VSS I believe it is called), tach bounced a little & no speedo below 30mph, brake & ABS lights stayed on constantly. I lost the crank position sensor about a year ago. The tach was bouncing around a bit & then quit working. Piston Slapper is right on with the install instructions.

 

[dlange]

Mine was doing it and all I did was clean the battery terminals, and it stopped. Maybe I was lucky, but it fixed mine.

 

[hoverlover]

crank position sensor

If you can feel the engine surge with the tach movement CHANGE the crank position sensor!