Tach problem

[airman]

My tach works but does not read wright it is always about 1200 rpm fast.Have any of you had this problem ? If so can it be fixed ? I know there is a filter between the distributor and the tack but I'm not sure what it does.Thanks for your input.

 

[G Winter]

The tach in my 90 is also off some. Not sure how much, somewhere between 50 and maybe 500 rpm.. seems to be farther off the higher the rpm. Hope we get an answer here.

Glenn

 

[Hrtbeat1]

My tach works but does not read wright it is always about 1200 rpm fast.Have any of you had this problem ? If so can it be fixed ? I know there is a filter between the distributor and the tack but I'm not sure what it does.Thanks for your input.

Most likely it is the filter you describe. It is located on one of the mounting bolts between the engine and trans ... upper on the drivers side.

Mine was acting up also. Tried to find a replacement, but even GM said they were discontinued. I did find out that on the '90 and '91 cars its not really needed since these cars have an analog tach. Not sure about the earlier years because these are digital. The filter is basically an EMI shield. Mine had bare wires showing on one side of it. I removed the filter and reconnected the wires where it was (bypassed it) and the tach worked fine with no ill effects. I was given some mis-information by a member here and by a shop that works on the earlier digital dashes that my dash needed to be rebuilt/replaced. Not sure if they mistakenly thought I had a digital dash or they were just trying to make a buck (actually a few bucks.)

Hope this helps.


G

 

[jimmers]

Most likely it is the filter you describe. It is located on one of the mounting bolts between the engine and trans ... upper on the drivers side.

Mine was acting up also. Tried to find a replacement, but even GM said they were discontinued. I did find out that on the '90 and '91 cars its not really needed since these cars have an analog tach. Not sure about the earlier years because these are digital. The filter is basically an EMI shield. Mine had bare wires showing on one side of it. I removed the filter and reconnected the wires where it was (bypassed it) and the tach worked fine with no ill effects. I was given some mis-information by a member here and by a shop that works on the earlier digital dashes that my dash needed to be rebuilt/replaced. Not sure if they mistakenly thought I had a digital dash or they were just trying to make a buck (actually a few bucks.)

Hope this helps.


G

So your saying that I should remove the tach filter? Im having the same problem with my 90.

 

[G Winter]

On a bellhousing bolt?

Glenn

 

[Hrtbeat1]

The tach in my 90 is also off some. Not sure how much, somewhere between 50 and maybe 500 rpm.. seems to be farther off the higher the rpm. Hope we get an answer here.

Glenn

Mine was acting much the same as yours. Very close to being correct at idle but during a WOT shift I was seeing around 7000 RPMs. I know I wasn't spinning it up that much. I tested bypassing the filter first by connecting my scanning software up and looking at the RPMs. I also took one of those cheap 2 3/8" aftermarket tachs and hooked it up directly to the tach output from the distributor. I then went on a road test and compared the readings, they were very close (hard to read that small tach.) After my little test I did the bypass and compared the dash tach to the scan software tach reading .... they were both right on. Good enough for me. I left the bypass inplace and didn't worry about it anymore.


G

 

[Hrtbeat1]

So your saying that I should remove the tach filter? Im having the same problem with my 90.

Not saying that you should. Just giving my remedy.

 

[Hrtbeat1]

On a bellhousing bolt?

Glenn

The filter is inline from the tach output on the distributor to the dash input at the tach. It looks almost like a condenser from an old points type distributor, only larger. About an inch in diameter and about 1 1/2 inches long with a wire in either end. The mounting bolt was one of the bellhousing bolts (it has a metal band around it with the tab ends of the band for mounting.)


G

 

[G Winter]

Thank you.

Glenn

 

[airman]

Thanks for the info I will try it.Its good to know where you can find good help !!! Your cars look great I need to get some pitures of mine when weather permits.Thanks again.

 

[airman]

Did not work

I bypassed the Tack filter but it still does not work wright still reads about 1500 high,any more sudjestions ?