Tach bounces when warm
 

Gents, I have been asked to help a guy with his MS and thought I would ask here to see if any of you have run into this before and have any idea's. Car is a 1995-6 1.8 with a mini cooper charger on it. M/S1 3.0 pcb, built by a 3rd party as per brainiacks write up.

It runs fine but the tach is playing games. When cold everything is ok, but after 2-3 min of running the dash tach starts to hop all over the place. The M/S gets a clean signal all the time and the datalogs come back fine with no spikes or odd readings. But the tach is hopping all over the place. Now this is a 1.8 so I know the coils work a bit different than mine (I am 1.6) so just plugging my MS in with his map in not an option right? Any idea's?

Bad earths, even stock cars do it, clean up the ground near to the throttle body.

From the year it's likely still a 4 pin coilpack, so the tacho is fed from them, you could build a tacho output circuit and feed it from the ECU, that may help, but I'd do the above 1st.

Your dash tach gets its signal directly from the coils...

Sorry, read your sig and not the post ;)

it's a 95-96, so it may be a 96 with a 3 pin coilpack and fed from the ECU, then again it may be a 95 and fed from the coilpack ;)

Yeah, sorry I don't know the exact year. I "think" its a 95 but not sure. I'll have a look at the grounds then and see if there is anything there to be corrected

Look at the coilpacks. Specifically the low-side electrical connectors going to them. Does each connector have three or four wires going to it?