Tach not right


New Member
My stock tach is off by 500-1000rpms all the time.At idle it reads 1400rpm while it is actually idling at 750rpm.While cruising at 2000rpm it reads 3000rpm:(

Is there a way to fix this?Wires to check?

Casper's electronics will fix the tach, and the stock boost gage. They won't ever be real good, but Casper's can make them tolerable.
Is it hard to hook up an aftermarket tach(autometer).For the longest time I thought I was over revving the motor till I finally checked it.Screw the factory tach!!
Yeah, mine reads about 1000 to 1500 too high also. I've owned 7 of these cars and this is the first one that did this. Anyone know why it would do this?
I'm not sure what the factory tach runs off of...(some chip board on the side of the passenger fender i believe...map sensor???)

anyways 7 years ago I had the tach fixed by a Buick tech...now it reads perfectly with the scan tool...so does the boost...I think they both run off the same setup

all of the TRs have this problem...something happens over time to the circuitry and it causes crazy readings...
For the longest time I thought I had deep gear's in the car like 3.73 or 4.11's by looking at the tach.At 75mph it was reading 3400rpm.