My tach needle and speedometer needle twitch whenever i let off the gas and hit the brake. The check guages light flashes for a split second. I notice it most on highway. If i tap the brakes on the highway the needles flicker, then if i tap them again right after they dont flicker, i have to accelerate and then tap the brake to make them do it again.

Car is a 97 M6 T/A. Just Intake/Exhaust/cutout.

Has anyone else had this? Is it a PCM problem?

 

I'm curious to know what the voltage gage is doing during this problem. I believe you're either loosing the power connection or ground to the instrument cluster.

 

i did watch and the other guages (fuel, water, oil, voltage) never moved. Maybe they just are not a long enough sweep to really notice?

I would try again, but the reason for my posting of this is that my car died one night, and i thought it was an opti. So i replaced the opti and now its all back together and it still wont start.

I had lots of cooling problems, which ended up being that my fans wouldnt kick on, so after replacing every hose and the radiator, i put in a manual fan switch. The reason for the fans not working was unknown (all relays were fine) but after i read into it and saw that my fans didnt kick on when the A/C was on then that could have been PCM related.

Now i am thinking my PCM **** the bed totally. If the guages were doing that due to a bad PCM then it might make sense

 

The PCM is not the problem with the gages. It merely receives data from the gages, it doesn't control the gages.

Since your gages went funky AND you no longer start, I suggest you start looking for voltage and ground at several key areas. Just to start.