Help needed: Changed coil pack, now tach has gone nuts

[Grand Moff Joseph]

So, one of my coil packs went out today, and I had to replace it. Now, my tach is jumping around like crazy. Note that my tach is a wired up one, as I recently did a cluster swap - the tach is spliced into the wire that comes directly off of the ICM, and has been trouble free until now.

 

Will an idle re-learn fix this, or what else may be the cause?

 

Thanks!

Joe

[Crazy K]

is it reading too high? too low? or jerking beteen 0 and the right rpm?

or just flying all over the board?

 

did you damge the wire splice you made?

[Grand Moff Joseph]

The tach is jumping everywhere. What's weird is, it reads perfectly fine at idle, and still works fine at slower speeds (<40), but at speeds above 50, it starts jumping horribly.

 

I had the coil changed at my mechanic's place, as I was on my way to work when the coil blew, and did not have time to do it myself. I don't think they would have dsmaged it, but I guess it is possible.

[jeremy]

to powertrain

[5speedz34]

This might give you some insight......

 

When I put the newer 3x00 starter on my car, my tach jumps everywhere when I start the car. Since the tach gets it signal from the coils, and the coils are so close to the starter; I guess that starter draws so much power that the wire gets the signal from the starter when it's starting!

 

I would check your wiring and see if it's maybe touching, or is to close to something.

[95oldsVan]

If any wires are touching the alternator or something else that it shouldnt be,it can make your system go nuts...this is more common with digital dash clusters..if you put the wires too close to an alternator with a car with digi dash its gonna go crazy in there...seen this happened on a Z24 2.8 cavalier years ago.Just tyring to show how wires too close to other electrical parts can sometimes cause problems like that.