I've noticed tonight that when I was on the highway on my way home doing a consistent 70mph that my rpm needle would jump anywhere from 500 to 1500 rpms and back to where it should be running. Even at idle on a red light it would jump from around 800 at idle to around 1,300 rpms. however, the car itself doesn't run any differently. Any suggestions? Bad ground wire someplace?

 

Check the front engine ground and tranny ground, and if that doesn't fix the problem, inspect the wireing from the distributor to the ECU, there could be a loose pin on one of the plugs.

That happened once to me, and it was the tranny ground, it was just loose enough to rattle around and loose contact for fractions of seconds causing the tachometer to act goofy.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92TypeR &raquo;</TD></TR><TR><TD CLASS="quote">Check the front engine ground and tranny ground, and if that doesn't fix the problem, inspect the wireing from the distributor to the ECU, there could be a loose pin on one of the plugs.

That happened once to me, and it was the tranny ground, it was just loose enough to rattle around and loose contact for fractions of seconds causing the tachometer to act goofy.</TD></TR></TABLE>

i was thinking tranny ground also, because it isn't doing it all the time. I've never seen it do it as much as it did tonight. I've seen it jump once in a while but not like before.