[VTramcharger90]

A few months ago speedometer in my 90 RC stopped working over 52mph.  Works fine until you reach 52 and then just stays there until you decelerate.  It also started stumbling/ backfiring sometimes which has gotten much worse with the cold weather.  Seems to happen less if I turn OD off. 

I've replaced both speed sensors which didn't change a thing.  Replaced the connector for the one on the transfer case.

Which sensor reads speed? 

Any ideas?

 

[Elwenil]

The one on the transfer case.

 

[dodge82273]

agreed speed is transfer case , antilock brake is rear axle .. unless its a wiring problem the 2 things are unrelated , I'm gonna guess a vacume leak would cause a problem to worsen with cold temps , check codes first . 

 

[VTramcharger90]

I thought they were related because they started about the same time but you got me thinking maybe not.  So I swapped in a spare cluster I had and the speedo seems to work fine. 

I fixed some really nasty connecters and inadvertently fixed a bad radio static issue.

Now need to figure out why it's running like poop.

 

[dodge82273]

pull codes if any , then check with vacume gauge .

 

[VTramcharger90]

No codes.  I should replace vacuum lines because they look pretty aged.

I think I found it.  I swapped out the coil with the original Mopar and it ran great all day.  I had replaced it with an aftermarket one years ago but kept it in case.  Looks like the aftermarket only lasted a few years.