Ok here's the deal. I am running a stock b18a1 with a fresh rebuild. Everything is running great and smooth with no codes. Now the only issue that I am having is that after it warms up the needle on the temp gauge want to bounce. Now to make things weirder is only does is when decelerating. ie. Achieved a certain speed and let off the gas and the needle starts to bounce. Push the gas or clutch it stops bouncing and goes back to normal. What could be the cause of this.

 

check the ground on the thermostat housing (upper rad hose end). if thats not it, try ADDING a ground to your valve cover to chassis.

i had that problem, among other weird gauge things, and another ground solved it instantly.

by any chance do ur lights dim when u press the brake? or clock light dim ALOT when you turn on headlights? anyways try it at night, headlights on with ur car on and i bet it will be solved.

 

I'd agree with the ground issue, or a bad gauge cluster.

 

i thought that when i had my problem, but sure enough it was a ground!!! it doesnt make any since really, but oh well haha.