I just bought a 98 z28 m6 after getting it home i noticed that it was idling a little high for being warm 1000-1100rpm so to make sure i hooked my scan tool up and it's really idling right around 800rpm. obviously it's a gauge problem, but does anyone know what is specifically wrong, i know some of my other gm cars have had stepper motor problems, and i've also seen a speedometer needle move on one of my chryslers. has anyone had this problem before?

 

Mine does the same thing. Tach reads@1000, scanner shows @800. I just try and remember it's reading high and dont go over 4800 RPM....

 

these gauges are pretty inaccurate, just wait until your gas gauge says 1/4 and you run out of gas... thats a fun one

 

Story of my life with mine

 

Why should i not go over 4800rpm?

 

I said me, not you. Redline is @5000, so if my tach says I'm at 4800, it's actually 5000, which is the @ redline, and I don't really like to redline an 18 year old engine with 180,000 miles on it. Thats just me, though. Others run the dog snot out of theirs till it blows the rebuild it. Mines my DD.

 

that would be me! ...and that would be why I have two "DD" vehicles, when one breaks I drive the other

 

Not to nit-pick man, but your actual rpm is 200 lower than your tach is reading. So 5000 on the tach is really 4800. So instead of limiting it at 4800, you can go to 5200.
There, that just bought you an extra 400 rpm you didn't know you could use!

 

Well you get the point. Never said I was good at math....

 

I have a fresh ls1 which can safely rev to 8000k rpm, and the rev limiter is lower than that, so I'm not scarred. Then again i drive all my cars like a pissed off teenager every now and then, but i would never hold it on the rev limiter like some ricer.