Tachometer Jumping Rpms

[RacerX4g64S]

Now befroe you reply please read.

Tachometer Jumping RPMs not engine. I know it not the IAC as idle is ok, engine is smooth. What happens is when idling at a light enging running smooth and my tach needle will jump From 850 to 0 up and down. Again it stress the engine is running smooth. Then when crusing the rpm will jump from 2500 to 3250 just the neddle not the engine.

I noticed this happens on hot days.

My question is how does the tach get the rpm; speed sensor, cam/dis sensor?

Any Ideas?

Thank you

[GOOSEY2099]

what year is your car? That sounds like a bad ignition failure switch located on top of the intarke manifold(it has 4 wires)

[RacerX4g64S]

its a 95

[4-G-rim]

RPM signal on 94-95 is from the distributor.

[Stewi]

Im not sure if that matters with the distributor. If the 7g uses an ignition failure sensor, I would check that first. Our RPM signal doesnt come from that sensor, but it sort of goes thru it, and it always messes it up, even with the AEM EMS and the EVO motor it screwed it up.

[Serstylz2]

Now befroe you reply please read.

I have to READ before replying?! GTFoutta here!!

:smt044

[mko]

Now befroe you reply please read.

Tachometer Jumping RPMs not engine. I know it not the IAC as idle is ok, engine is smooth. What happens is when idling at a light enging running smooth and my tach needle will jump From 850 to 0 up and down. Again it stress the engine is running smooth. Then when crusing the rpm will jump from 2500 to 3250 just the neddle not the engine.

I noticed this happens on hot days.

My question is how does the tach get the rpm; speed sensor, cam/dis sensor?

Any Ideas?

Thank you

My tach does the exact same thing every once and a while, but it goes away in few seconds. Pull your cluster out, look for oxidized contacts, or anything that could cause bad connection. There are 3 or 4 screws on the back of the cluster that hold the tach in place but also they conduct the power supply and the rpm signal to the coils inside the tach.

[RacerX4g64S]

I will take a look thanks!

[lonestar22]

my 7g used to do that before i replaced the transmission