So, inconsistantly my speedo and take will sometimes "hang" at a specific RPM and speed during hard acceleration, then catch back up a moment later. The car pulls smooth, so it's not like it's hit a wall at that point. This doesn't happen all the time just every once in a while.

Has anyone heard of this before or have any idea what might be going on? Really could use some advanced tech assistance here.


Car is a 1995 Z28, LT1, 383, 6-Speed, 24x conversion, D1SC (14#'s of boost), AFR 227 heads, very large cam, super Vic jr intake. 700 RWHP.

 

Are you driving the 97 tach and speedo from an LS1 PCM? Have you checked with other 24X users regarding a possible interface problem?

 

It's the factory speedo and dash from my 95 Z28, and yes the 24x conversion uses the late models (01-02) LS1 PCM. I have looked and no one with the 24x has had this same problem that I can tell. My thoughts were the same thinking that the two were not speaking correctly, but there is no solid evidence of it.

 

The wiring diagrams for the later year LS1 F-Bodies show a module that is part of the instrument cluster, labeled "solid state logic" and "class 2 serial data". The wire from the PCM to the speedometer shows a direct connection to the speedo, but also has a branch to the solid state logic module. Might be some sort of mismatch there.... just a guess.

 

Fred, thanks for the replies. There could be some sort of mismatch, but it would likely be more evident on a consistent basis. It never does it during normal acceleration. Even on hard acceleration or WOT it only does it maybe 1 in every 20 times.

The fault seems what I would think as something failing or a connection that may be partially loose, but I have no idea what it would be.