Hi new member here, I’ve already gone through two new speed sensors, cleaned the electrical plugs behind the instrument cluster and the plug for the speed sensor but didn’t work. With the new and old speed sensor it would work for a short time but for driving a few miles or when I hit a certain bump the speedometer will start jumping again, I’ve also checked the speedo gear and it looks ok. Anyone?

 

One of my other cars had a jumpy needle, but I'm not sure it jumped the same way yours does. Mine is a mechanical speedo with the cable that goes from trans to cluster and turns gears in the back of the cluster. In that case damage along the cable can make it jumpy. Mine was not correctly secured after exhaust work and it partly melted the cable.

I'm not convinced your 98 will have a mechanical speedo. If it is electrical then, after what you've done, I would make sure of my grounds, and consider if there is something else injecting noise into the sensor circuit. It would be counting little voltage spikes sent from the sensor and the gauge converts the count/time into a needle position. Does it jump upward like an extra pulse or downward like a missed pulse?

 

I say it jumps upward like an extra pulse. Like When I’m driving on gravel after a short drive the speedometer will start jumping over +100 mph, it did the same thing when I was sitting at a red light once. I noticed it started jumping right after I cleaned the Idle air control valve but I don’t know if it has anything to do with it.

 

Update: I’ve cleaned out all the ground wires I could find but didn’t work. I’m thinking of putting a cluster gauge from another Cherokee to see if that will work.

 

Yours might be late enough to fall afoul of the lead free solder bull. In that case a cluster could contribute. The fake solder cracks under vibration like in a car or an airplane and then you start getting all sorts of weird electrical problems.

 

Update: I’ve got another cluster from the yard for 36 bucks, tried it and didn’t work. It seems to only get worse the more I drive it, and also my transmission will shift funny in low speeds when The speedometer starts acting up.

 

I think what is happening is you have a short developing. You will need to trace your wiring, or replace the speed sensor wire completely and that will probably fix it

 

What’s weird is I took the jeep to the OBX yesterday (about 30-40 mile ride there) the speedometer will jump most time but when coming back It only jumped I say 3 or 4 times and when going down on my gravel driveway I didn’t jump at all. It was weird because the speedometer would most likely jump when on my gravel driveway.

 

That just verifies the assumption you have a wiring problem

 

Newb. Does the OBX mean you coated something with mud so that the intermittent short was blocked by a layer of mud?

 

I wouldn’t be here if I did such a thing lol.

 

Hm. That might not have come out right. I meant by that: I am a newb and don't know what OBX is.

 

Outer Banks in North Carolina.

 

So then I'm thinking more sand than mud.

 

Btw i found the problem few months back, it was the ground wire bolted between the fire wall to the top of the engine for the dashboard. Thanks for the help!

If ya need anymore sand or mud let me know