What would cause your RPM Tach to jump all over the place?

 

sensor is bad or wire is loose, or cluster is bad

 

Cause I figuer it would be the igniter, so replace it, but that wasnt it then put a cap/rotor on it..... that didnt fix it, but made it better so I will look into the wires again.....

How would the cluster go bad?

 

Are you running any kind of obd2 to obd1 harness ?
If so, what year/make/model is the vehicle ?

 

solder joints and what nots can go bad in clusters ive had it happen twice before somthin stops workin on it and I replaced everything else and it still didnt work, last ditch option replaced the cluster, and all was fine.

 

1995 DX Hatch LS/Vtec Swap GSR Ecu has a sir cluster in it....

 

check your ignition control modual (sp.. **** forgot how to spell it), ICM, .. my car used to backfire really bad and tach would go crazy out of nowhere..

 

???

 

I have checked the icm I just put a new one in. It didn't make sense. The car pulls great just tach all over the place. So could it be the cluster?

 

???

 

?? ?? ??

 

it never hurst to have an extra, get one and try it if thats not it then sell it on ebay.

 

Yeah wish I didn't give away all my old sir eg parts when I had it LOL I will see what I can do

 

When i finished my build i had a couple of electrical issues, one of the symptoms i saw was the tach jumping. Although i believe that this would cause more problems than the tach, i narrowed my problem down to the earth point on the thermostat housing. I had neglected to torque it up after i put it on finger tight.. Might be worth checking

 

Another thought is to check the shoe connectors on the icm in the distributor ensuring you have a good connection to the icm. I have seen this be an issue at times! Also trace your grounds and ensure they are clean and secure.