'88 L98/700R4.

I'm having trouble tracking this problem down. With the engine running, the tach bounces between 3000 and 4000 RPM. I just had the engine apart and while I was at it I removed the entire engine harness, stripped all of the tape and loom, inspected and repaired any damage I could find. I thought I would find the problem that was leading to the tach issue but I didn't find anything.

Has anyone had this problem before?

 

I should mention it's got a new cap, rotor, plugs and wires and runs fine.

 

Bad connection at the coil for the tach signal? Hows the printed circuit board look?

 

Connection is tight at the coil and distributor plugs. Haven't pulled the cluster out to look at the circuit board.

 

Hit the electronics board here at TGO. Up in the sticky's is a long thread on fixing the tach driver board. A resistor goes bad which is easily replaced.

RBob.

 

I had to do the same fix on my tach that RBob is talking about- it was reading way high, but didn't bounce like you're describing. My bad for pointing you in the wrong direction. I didn't realize that was another symptom of the diode going bad.

FWIW, it's a really easy fix. If you've gone through your wiring harness, the fix will be pud for you.

 

Great, thank you both. I will get busy.