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Dec 8, 2011 | 04:11 PM

steven mack

Thread Starter

Drifting

Joined: Oct 2006

Posts: 1,328

Likes: 14

From: Stafford Connecticut

Tach

My Tach is reading wrong.It will go to 3500 RPM then stay there or drop.My scan tool reads 4500 RPM and climbing when this happens.Any ideas of what would make this happen. could the tach readings on the dash effect my computer in the Vette.Once again the tach readings are right on the scan tool.

Dec 8, 2011 | 04:54 PM

rodj

Le Mans Master

Joined: Aug 2000

Posts: 8,838

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From: Australia

Tach filter maybe?

http://forums.corvetteforum.com/c4-g...1990-vert.html

Tacho is display only ,ECM gets RPM from different source so no connection between the two.

Dec 8, 2011 | 04:54 PM

DBo

Instructor

Joined: Sep 2009

Posts: 182

Likes: 1

From: Greenville SC

I had some highly erratic tach readings with my 84 that I fixed by replacing the tach filter. Easy fix, pretty cheap. I think that I bought it at Eckler's. Dave

Dec 8, 2011 | 04:59 PM

rodj

Le Mans Master

Joined: Aug 2000

Posts: 8,838

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From: Australia

Quote:

Originally Posted by DBo

I think that I bought it at Eckler's.

For the budget conscious
http://my.execpc.com/C4/4A/rodney1/corvette/

Dec 8, 2011 | 05:54 PM

steven mack

Thread Starter

Drifting

Joined: Oct 2006

Posts: 1,328

Likes: 14

From: Stafford Connecticut

Tach

Thanks guys I'll get one I hope that's the problem.Looks like an easy fix.I'm glad to hear it's display only and doesn't effect the running of car.

Last edited by steven mack; Dec 8, 2011 at 05:59 PM. Reason: add info

Dec 8, 2011 | 08:46 PM

corvetteronw

Race Director

Joined: Feb 2003

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From: Kingman AZ

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St. Jude Donor '06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16

What year is the car? 90 and 91 are known for this problem and a new tach filter does not usually fix the problem.
The fix is done by repairing the tach portion of the instrument panel.
At work now and do not have access to my home computer files.
Maybe a search here will help you out.

Dec 8, 2011 | 10:03 PM

steven mack

Thread Starter

Drifting

Joined: Oct 2006

Posts: 1,328

Likes: 14

From: Stafford Connecticut

I'ts an 88 Thanks

Dec 9, 2011 | 02:35 PM

steven mack

Thread Starter

Drifting

Joined: Oct 2006

Posts: 1,328

Likes: 14

From: Stafford Connecticut

Well I decided to check the connections to my Tach filter.I didn't know the wire from the distributor to the other end of the filter was a blade connector fitting.So I unplugged the fitting to look for corrosion then plugged it back in.The Tach works fine now.Sometimes you catch a break working on these cars. Thanks for the link rodj.

Last edited by steven mack; Dec 9, 2011 at 02:47 PM. Reason: add info