ive asked this before but i didnt really get a clear answer. anybody know why my rpm will read higher than it is and other times it will bounce between numbers when im keeping a steady speed?

 

Bad Ground?

 

what about only when the car's stopped..?

like, im at a red light, and the needle will start moving up and down, and the car shakes bad, so i gotta hold the brake and give it gas at the same time, cause it's turned off on me before (i have an auto)...

but she pulls like a horse, once i get going, what do you think it is?

 

I have recently had that same problem, it was my distributor timing was off; in fact it was so badly off that I had to take the distributor cap shaft out and re-index it.

I believe it was the mechanic at the Nissan dealership that was working on my car; he would not let me back to watch him… Go figure!

 

Could also have a power problem. My buddy had an aftermarket tach and when his battery was going out it would bounce. Could have a battery or altenator problem. Or a wire shorting. Those are easy to check I would start their.