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tach erratic

Posted: Mon Sep 01, 2008 9:26 pm
by cycle252
Ok so i know this has been seen elsewhere but i just cant seem to find the answer to my problem. I have a MS-II running the newest code on a factory tbi 4.3l chevy v6, basicly just the basics you know, slightly worked heads and cam (really to big for my app but it will do for now), and intake. Now the problem is the tach signal jumps like crazy anything above around 2500rpm it has the HEI ign and right know its just running in limp (meaning the timing advance wire is not hooked up) so i can start it and make sure its wired up right. Right now the tach is being run off the tach wire on the coil and not off the ign module itself (HEI 8 ) for some reason it didnt work with the R pin for some reason, and i mean not at all got 0rpm and never started, well you get the idea. So far Ive done the MSnS-E mod (first used a 1.3k res on r12 then the 390, both gave the same result), so any help is welcome. Attached is a quick datalog of the first run and the base tune that i can up with. as well as the msq file

Re: tach erratic

Posted: Tue Sep 02, 2008 7:03 am
by cycle252
Also right now the c30 spot is empty i did read that with spikes it might be necessary, but i really need more info about it before i decide to try it. also as of right now the ground from the ign module is just grounded to the sensor ground on the ecu, to me its not noisy per say. Its just erratic above 2500.. seems to work fine below for the most part??? i really need some help figuring this out
Thanks in advance


....side not c12 is off too, should i install it?
....also does anyone think that the coil could be losing some ground signal causing the spikes, i notice that the tach count goes back to zero right before it jumps all over the place, the coil might not be grounded very good, so il check that when i get home.