This is an excerpt of my post over at msefi.com. :

I had my first problem today. It was a hot day, and I started my car as normal.

Ran about 2 miles, all of a sudden, the tach went to zero and bounced up. It was then fine for a bit, and then it resumed, surging and dying every few seconds, with the regular tach and the megatune tach going crazy (the megatune tach is not connected to the the stock tach, which reads off of the coil)


Pulled over, car died. would restart and run for about 5 seconds then die again.
Wiggled the wires, no effect. Disconnected the ignition advance relay, no effect.
After about 5 minutes, restarted normally, and i took off while taking a datalog. 5 minutes later, it happened again, even worse. Followed the same procedure with the same result. I looked over the datalog and saw the rpm's drop to zero very often.

after i watched the datalog, i tried to start the car again, and it started normally and ran normally the entire way home (about 30 minutes)




Ignition module?

 

Yep! or a bad earth somewhere

 

was the exhaust poping to?? mine did this same thing lastnight, its not sitting on the side of the road about the 10th time it did it yesterday to, its either my coilpack which i just replaced or the ignition module ^.^

 

i had that problem with my car before, and it was the coil. It finally just gave up and wouldnt start. Took it out and it had a crack all the way across the coil. I knew it wasnt a ignition module, because i have a msd 6al box

 

I'm sure you've seen the stickys at the msefi forum. The "8-pin hei hot start" sticky is about this exact problem. I did the 'transistor mod' on my optoisolator input board, and it works great. I was having all sorts of fits(as you heard all spring), and it turned out to be the el-cheapo ignition module. It hadn't worked since the day I installed it.

It dawned on me one day when my tachometer mysteriously stopped bouncing around. The engine ran remarkably smooth that day, and when it went back to crappy, the dash tach started getting all jumpy again.

My thoughts are a jumpy tach = bad rpm signal = bad igniton module = run like crap...if at all.

A borg-warner ignition module later, my tachometer is always smooth as glass.