When I am cruising along at 50 mph, I get a strange pattern in my RPMs... it will bounce between 2500 and 1500... Whats up with that? It doesnt seem to do it at any other speed, only when I am cruising at 50...

 

hmmm... hows the speedo cable? Does the speedo bounce around at that speed? Ive heard of similar problems caused by the computer unlocking and locking the tcc becuase the speed signal from the vss bounces all over the place.

 

The speedo sits right at 50, if I even go a little over about 52-53 or so the tach stops jumping... Its wierd. I put injector cleaner in and it was doing it a little at 40 when that was in it. or at least it seems like it. I dunno.

 

does the engines speed vary with the tach reading and is their a decelerating/surging feeling as well when this happens?

 

It stays at 50, the RPMs just jump around like that. The only feeling I get is the slowing and reving of the RPMs. The speedo may move a little but the tach jumps back and forth so much there is no time for the car to actually slow down.