tach rpm jump

[FGR]

so last week my tach started dancing after 2000rpm and stop after 3500 but i wouldn't do it during hard acceleration. ( its just the tach not the motor, car runs fine) it also the problem started right after getting my valves adjusted and the dizzy adjusted to the motor. (dizzy is new) so i did some research and the solution i can up with was the cluster changed that out it stopped but i have a denso cluster originally now i have a ns i believe in there so my miles are way off. anyways so a few days ago i started the car from a cold start and it danced again but it goes away after its warm. im really confused with it now thursday of this week im going to clean the thermostats ground for the dizzy and maybe sway out the ignition control from my old dizzy and see if it cures it all i heard the speed sensor can do this dancing rpm gauge. any one had this issue before any help would be appreciate. thanks guys f22a6

[Losiracer2]

its the igniter unit going bad

[FGR]

thats what i figured its shitty thought because its like maybe a month old

[johnl]

thats what i figured its shitty thought because its like maybe a month old

I had a similar experience shortly after purchasing my car some years ago. The igniter burnt out (car instantly dead by the side of the road), and the replacement igniter lasted maybe a week or so.

The igniter is damaged by excessive heat, heat is generated within the igniter in use. If the bulk of the electrical energy fed into the igniter cannot flow 'freely' through it, then excessive heat builds up in the igniter (that energy has to do something...). Excessive resistance in the ignition leads acts like an electrical 'bottle-neck', so if the leads are old and above spec resistance it's a reasonable bet this is what caused the original igniter to die, and now is in the process of killing the replacement.

Check lead resistance, if it's above spec then replace the leads. Hopefully this is the cause and will fix the problem of serial igniter failure, but it's probably too late for the sick igniter currently in there...

I can't promise you that this is your problem, but I wouldn't be surprised.

[cb9love]

i have had aftermarket ignitors be dead on arrival,
especially the airtex from autozone.
I am now using a old oem one with a spare in the glovebox.

[BreckAConner]

I had this issue a while back, I'm glad I know what it is now. I replaced the dizzy, but I still have the old one. I guess I can just buy that part and replace it and reuse that dizzy if I need to.