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I got my 1990 L98 running well. The problem i have now is with my Tach. At idle the needle is at about 4k. The engine is idling at 800 rpm according to my timing light. When i accelerate the tach pegs out as far as the needle will go. I know its not spinning 6k rpm's. Where is the tach getting its info from ? I replaced the pick up coil and ignition coil as well as plugs wires cap and rotor to get it running. Any help is appreciated.
Sounds like a bad tach filter..This is secured to the top bolt of your bellhousing and looks like a small tube about 1 1/2" long...When these go bad the tach does all sorts of strange things. You can get them from most Corvette parts sites...WW
I got my 1990 L98 running well. The problem i have now is with my Tach. At idle the needle is at about 4k. The engine is idling at 800 rpm according to my timing light. When i accelerate the tach pegs out as far as the needle will go. I know its not spinning 6k rpm's. Where is the tach getting its info from ? I replaced the pick up coil and ignition coil as well as plugs wires cap and rotor to get it running. Any help is appreciated.
A known issue for the '90 cluster. There are several posts regarding the issue and I'd suggest a very simple search which should land several of them. Determine which is maybe the best resolution for you and move forward. You can eliminate any of the threads that suggest "tach filter"!
Different search terms of course will get you different results. Use the "search this forum" at the top of the C4 "performance" threads and also in the "general" threads.
"1990 tach repair" will get you a couple good reads.
The Tach on the 91 I bought in October has similar symptoms, but I knew that before I purchased and wasn't on my immediate repair list. Keep in mind it could also be because of a bad resister on the circuit board behind the instrument panel. When I'm ready to deal with it may try the filter first just hoping to get lucky.
08-02-2013, 08:05 AM
Tach Problems
