Ksths2

iTrader: (1)

Hey everyone, I’m finishing up the install of a MSD Timing twister on my 02 C5 and to make a long story short when I start the car the factory tach now jumps all over the place even at idle. I’m assuming its something to do with the tach wire I tapped into for the MSD but I used the same tach wire I use for the Autometer shift light that works fine. (Its the tach wire under the dash on drivers side by steering column or kickpanel) The MSD instructions say to go to a "TACH OUTPUT. 12 VOLT SQUARE WAVE, 30% DUTY. V8 ONLY."

Any ideas? Like should I of went to a wire on the coil or something else? Please help!

The power and ground is good and the plug'ins for the cam & crank are good too as far as i know, for the 12volt + i tapped into the fuse block by the battery (10amp - #16 fuse = PCM)

Thanks!

PACKETFOCUS

iTrader: (2)

Hey Man-

Did you ever figure this out? I have the EXACT same problem on my 98 fbody. I installed a timing twister tonight and pulled the tach signal from the white wire that my other devices used. Now my factory tach bounces?

Ksths2

iTrader: (1)

Yep, unhook the tach output wire, it doesn't connect to anything. Its just for an "OUTPUT" like to run a shift light.

I felt dumb but relieved when they told me that and worked like a charm GOOD LUCK!

PACKETFOCUS

iTrader: (2)

LOL.. That makes perfect sense now. I hope thats the case. The documentation made me read that I needed to be connected to the RPM/Tach wire lol.. That would explain why my tach is off now.

Thanks a lot man. Cutting wires in the morning.