Tach reading wrong on my '91
Thread Starter
6th Gear
Joined: Mar 2007
Posts: 6
Likes: 0
Tach reading wrong on my '91
The tach on my '91 C4 (no option car except auto air conditioning) is reading about 2x the actual engine rpm. I do have another cluster but no the time to replace the existing in the near future. Anyone else w/ this problem or a solution?
Melting Slicks
Joined: Mar 1999
Posts: 2,830
Likes: 20
From: Las Vegas Nevada
The tach filter is located in the engine harness between the wiper motor and the distributor. The filter itself is a small barrel looking device with a tan wire leading to it. The filter should be mounted to the rear of the cylinder head if memory serves me correctly.
GM discontinued these filters a while ago. There is a guy that is making and selling replacement filters. I need to buy one so I was searching for the webpage when I stumbled onto this thread. When I find the web page I'll post it here.
EDIT: Here is the webpage: http://www.rodneydickman.com/CorvetteTachFilter.html
Anyone know why he only lists to '89 for the Corvette? Was the tach filter for a '90 and '91 different? I E-mailed the guy and asked him if he knows any reason the filter won't work on a '90 or '91 Corvette. I'll let you know what I find. This guy and Ecklers list to '89, then Corvette Central lists to '91?
We'll see...
GM discontinued these filters a while ago. There is a guy that is making and selling replacement filters. I need to buy one so I was searching for the webpage when I stumbled onto this thread. When I find the web page I'll post it here.
EDIT: Here is the webpage: http://www.rodneydickman.com/CorvetteTachFilter.html
Anyone know why he only lists to '89 for the Corvette? Was the tach filter for a '90 and '91 different? I E-mailed the guy and asked him if he knows any reason the filter won't work on a '90 or '91 Corvette. I'll let you know what I find. This guy and Ecklers list to '89, then Corvette Central lists to '91?
We'll see...
Last edited by VtVette; Aug 8, 2007 at 05:59 PM.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
"The filter should be mounted to the rear of the cylinder head if memory serves me correctly"
Is bolted on the top bellhousing bolt , drv side.
Black plastic cylinder approx 2" long with metal attachment bracket.
White wire from each end with brown connectors.Is not part of the main loom.
Pig to get at without pulling dist,no room to work down there past wiper mtr
Is bolted on the top bellhousing bolt , drv side.
Black plastic cylinder approx 2" long with metal attachment bracket.
White wire from each end with brown connectors.Is not part of the main loom.
Pig to get at without pulling dist,no room to work down there past wiper mtr
Burning Brakes
Joined: Aug 2007
Posts: 917
Likes: 2
From: Charlotte NC
Did you ever hear back from that guy ? i have a 91 that does the same, Ive searched all over and can not find a filter for it....
The tach filter is located in the engine harness between the wiper motor and the distributor. The filter itself is a small barrel looking device with a tan wire leading to it. The filter should be mounted to the rear of the cylinder head if memory serves me correctly.
GM discontinued these filters a while ago. There is a guy that is making and selling replacement filters. I need to buy one so I was searching for the webpage when I stumbled onto this thread. When I find the web page I'll post it here.
EDIT: Here is the webpage: http://www.rodneydickman.com/CorvetteTachFilter.html
Anyone know why he only lists to '89 for the Corvette? Was the tach filter for a '90 and '91 different? I E-mailed the guy and asked him if he knows any reason the filter won't work on a '90 or '91 Corvette. I'll let you know what I find. This guy and Ecklers list to '89, then Corvette Central lists to '91?
We'll see...
GM discontinued these filters a while ago. There is a guy that is making and selling replacement filters. I need to buy one so I was searching for the webpage when I stumbled onto this thread. When I find the web page I'll post it here.
EDIT: Here is the webpage: http://www.rodneydickman.com/CorvetteTachFilter.html
Anyone know why he only lists to '89 for the Corvette? Was the tach filter for a '90 and '91 different? I E-mailed the guy and asked him if he knows any reason the filter won't work on a '90 or '91 Corvette. I'll let you know what I find. This guy and Ecklers list to '89, then Corvette Central lists to '91?
We'll see...
Melting Slicks
Joined: Mar 1999
Posts: 2,830
Likes: 20
From: Las Vegas Nevada
Actually I did. He was quite confident that the filter would work on a '90 and '91 Vette. He is not a corvette Guru, so when he made his listings on his site he was under the impression that the L98 ended in '89. He said it should work with any GM HEI distributor. I'm going to order one. I'm not paying the $50-up people ask for a USED tack filter 
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Instructor
Joined: Jul 2002
Posts: 172
Likes: 0
From: jax fl
Bad tach
My 91 had the same problem with reading higher revs. I replaced the entire cluster as I had LCD readout issues also. This resolved mine and I did nothing to the tach filter. I tried switching the tach component from the new cluster into the old cluster and it still read high. Appears that the tach issue was in the actual cluster and not just the tach part.
Le Mans Master
Joined: Jul 2001
Posts: 5,297
Likes: 0
From: Stamford VT
Sorry to dig up an old thread, but has anybody else managed to resolve their issues? I'm having the same problem (tach suddenly decided to start displaying rpm that's higher than actual), but in all of my searching, I see a ton of recommendations for the tach filter, some recommendations for a new cluster, and yet almost nothing that indicates that people performed the suggested fix and got the results they were after.
There also seems to be an awful lot of confusion about what tach filter the 91 actually has. Everybody sells the barrel style for up to 89, and then the box style for 92+. Nobody seems to know squat about what the 91 actually has.
There also seems to be an awful lot of confusion about what tach filter the 91 actually has. Everybody sells the barrel style for up to 89, and then the box style for 92+. Nobody seems to know squat about what the 91 actually has.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
http://www.thirdgen.org/techboard/el...meter-fix.html
http://forums.corvetteforum.com/c4-g...1990-vert.html
Le Mans Master
Joined: Jan 2010
Posts: 8,553
Likes: 3
In nearly every case involving the problems common to 90 /91 cars, the resistors in the cluster have had to be replaced; replacing the filter has not worked as it does on other years
http://www.thirdgen.org/techboard/el...meter-fix.html
http://forums.corvetteforum.com/c4-g...1990-vert.html
http://www.thirdgen.org/techboard/el...meter-fix.html
http://forums.corvetteforum.com/c4-g...1990-vert.html
Tach filter
or
replace resistor
or
replace cluster with 92+ year, use same lcd display.
These are the options I read about here, all with different sucsess's.
I'm not in the mood to drop my steering wheel and replace the cluster. Mines an Auto, so I really don't care what the tach says I'm rev'g at.
