Weird Tach

[mike griffin]

has anyone ever been looking at their tach, while idling, and see it jump up like 1-2mm? cause i was watching it today, and the motor didnt rev any higher at all, the tach just went up 1-2mm and came right back down. kind of like a tiny boost spike. it did it a couple times on my lunch, and lots when i was in my driveway letting it cool down. its weird, just wondering if something might be wrong.

[Martin Raska]

I've noticed this happen very noticable when the turbo timer takes over control.  It seems to do with the state of the electrical system, which makes some sense since it is controlled that way.

[daniel_doluntap]

Mine does the same thing.  I thought it was wiring but i dont know, maybe one day when i have the time i will go under there and check it out.  When my alternator was going it would spike from 900 rmp's to 1500 rpm's and back.