90, Tachometer Problem
Thread Starter
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
90, Tachometer Problem
Gents, maybe you can help me with this one. I have a `90 in the shop that the tach. is reading way too high. It works but is too high. Is this something that is common with this dash? I have gone though the prelimanary checks and it points to the tach being bad, but I hate to replace the thing and that not be the cause of the problem.
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
Mine reads about 500 RPM too high. ('91 Vette)
There is no adjustment for it that I'm aware of.
There is a 'Tach Filter' out by the distributor that you could try changing before you change anything else.
There is no adjustment for it that I'm aware of.
There is a 'Tach Filter' out by the distributor that you could try changing before you change anything else.
Last edited by VetNutJim; Apr 21, 2006 at 08:12 PM.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
these tachs are not the most accurate...
if it was the tach filter, it would be reading really wack... how high is high? if at idle it's reading 5000, then the filter is hosed.... otherwise, I would either ignore the problem, or, get an aftermarket tach if you race (which is VERY important). Then again, the L98 has a built in rev limiter - it's called "TPI."
if it was the tach filter, it would be reading really wack... how high is high? if at idle it's reading 5000, then the filter is hosed.... otherwise, I would either ignore the problem, or, get an aftermarket tach if you race (which is VERY important). Then again, the L98 has a built in rev limiter - it's called "TPI."
Thread Starter
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
OK, sounds like the condition is rather common. It will read 500+ high at idle and then go way up when you rev it a little. The scan tool indicates a normal signal and reads correctly.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
According to Gordon Killebrew-most tach problems are because water entered the bulkhead connection-and the tach connection is on the bottom row.Although I agree with digi tachs not being all that accurate.
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