when idling, my tach twitches somewhat...any ideas on what causes this

 

My understanding it's the computer testing the tach and adjusting it. It jumps about 50 rpms right? Mine does the same thing. nothing to worry about.

 

Mine moves almost all the time when at idle.

 

All of your tachs should be rock solid at idle. No jumping around. Look for a P0336 CKP (Crankshaft Position Sensor) code. That will solve the jumpy tach. It may also throw some other codes pointing to communication to the ECM and VP44. The ECM uses the information it receives from the CKP in cooperation with other sensors to determine the fueling parameters. It's important that the CKP code be the first in the series of codes. If it is it is 99.99% causing the other codes. Depending on your climate it can be a breeze or a serious matter to R & R and it's location on the side of the block is less than admirable, tucked under the fuel filter canister and directly behind the starter.

 

I doubt that.
Mine's been jumpy at idle since day 1.


phox

 

same here

 

i agree with the above post because mine had a tiny bit of jump in it and when i replaced the CPS it made it stay completely still doesnt jump even like 10 rpms.......