I recently put headers on my car, experienced a near fatal problem. Extreme overheating. I broke the temp sending unit in half and didnt notice, next thing i know, my car is at 250 and riseing... none the less, that problem is now fixed. But now my tach. jumps around a bit. I dont think it did it before, but it is now. Its not much, just a few hundered RPM. And its not even all the time. Just, every so often. Do you think something may have happened to a wire somewhere? The tach is just goin bad? What??

 

Well check the connections. The tach wire is from the coil. Either in the cap or external coil depending on what you have. Make sure your harness is out of the way of your headers and not burned. Did you undo any ground wires or break any?

 

not that i noticed but its possible that i may have knocked one loose... i was watching today and anytime i would hit a bump of anykind it would jump. It would jump higher the harder the bump... so maybe i knocked a sensor of some sort loose. Nothing is close enough to the headers to cause any damage, i musta checked them a dozen times for that, they are clear. Where should i check?

 

Try to thump on the dash, close the door hard. Maybe your tach is taking a poo. Simulateing a bump on the dash and if it jumps it should tell you that it is not a loose connection in the engine compartment.