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So my car has been doing something real strange & not all the time,What its doing is the RPM goes up 200 to 300 Rpm when your setting still and at idle the speedometer goes up with it anywhere from 5 mph to 10 mph its acting like a tach and i have no tach:banghead: i talked to a Dodge tech about this and he says it kind of strange problem that he has never heard of,Any idea's

200 to 300 rpm's is really low, do you mean 2k to 3k?

So you have a tachless cluster, but the speedometer is rising with the engine fluctuations of approximately 200 to 300 rpm?

it idle's at 600 rpm or so and it goes up 200 to 300 rpm and yes thats what its doing

So it's almost like you have a loping cam. First thing that comes to mind is the IAC or power steering pump switch is faulty, maybe even a vacuum line is leaking.

Those are just wild guesses since the car is not in front of me so I can mess with it.

mine does that started after i installed the mpx60mm tb

But does your speedometer needle go up/down with the rpm's while the car isn't moving? I think that's what he's getting at.

Yes that what it does when it happens

Does the engine feel like its actually gaining revs, or is the cluster just giving a false increase?

the RPM'S do go up

NeonFlash wrote:it idle's at 600 rpm or so and it goes up 200 to 300 rpm and yes thats what its doing

ummmm - afaik: 600 > 300.
something is wrong in your story.

even 600 is too low.

Yeah the spedo has done that

Your speedometer gets it's "instructions" via the PCI bus wire. Whatever pulse code the pcm sends it, the cluster deciphers it and puts the needle there. So there has to be either something randomly shorting, or an internal PCM issue, that is affecting the IAC motor, and the speedometer. It might just be as simple as the VSS going bad. Possibly it thinks the car is in motion, so it raises the engine speed just like it does until you come to a stop and it idles down when in neutral. I would replace the VSS, and go from there.

VSS = vehicle speed sensor.

If you have an ATX, it is just below the battery area on the front of the ATX, IIRC.

MTX is in the differential housing pointing upward.

Thanks occasional demons and all others who responded to this ? i have decided not to worry about this issue at this time because its just so intermittent when it happens im just going to have to just wait and see and if it gets worse or the car blows up LOL of course then i will worry about it then,By the Happy Holidays to all

My car did it from day one even after 2 tranny swaps 2 ecu's a motor swap and even after installing Ms

My 01 did this, after CAI install. Put the car in neutral and it went back to normal.

Jenni wrote:

NeonFlash wrote:it idle's at 600 rpm or so and it goes up 200 to 300 rpm and yes thats what its doing

ummmm - afaik: 600 > 300.
something is wrong in your story.

even 600 is too low.

read it again... he didn't say it goes from 600 UP TO 300... he said it goes up 300 rpms...so, from 600 to 900

...and him saying 600 rpm idle...I think he is just estimating since he doesn't have a tach

Jenni wrote:

NeonFlash wrote:it idle's at 600 rpm or so and it goes up 200 to 300 rpm and yes thats what its doing

ummmm - afaik: 600 > 300.
something is wrong in your story.

even 600 is too low.

Nothing is wrong with his story. Something is wrong with your reading comprehension.

600 rpm idle, goes up 200-300 rpm, = 800-900 rpm.

hehe - i blame it on my english skills.
now that you say it - it makes sense in my head...
oh snap....


good - did i say: check all vac lines, the idle air valve and the tps/iac wiring.
check the spark plugs, spark plug wires and maybe the coil pack.

But none of that will make his speedometer go up and down. He has a tachless cluster.

This thread is full of so much fail lol.


His RPM's are jumping up 2-300 more RPM's over idle. In conjunction with his RPM's going up, his Speedometer is also jumping up, but he is not going anywhere.


Try another instrument cluster, just for the hell of it? Easy check..

Changing the VSS is cheaper/easier, if you don't have a spare cluster.