Intermittent tachometer
 

Anyone ever heard of an intermittent tachometer? Mine drops out once the car warms up. It seems to be based more on engine bay temperature than it is on coolant temp itself. It takes much longer to fail if I'm running down the highway than if I'm just driving around town. Figure about 40 minutes vs. 20, respectively.

When it goes, it's usually not sudden. It will start jumping around, going between 0 rpm and whatever the actual engine rpm is. There doesn't seem to be a pattern to the bouncing needle, and for the most part there seems to be no correlation with bumpy roads. The only control variable I could find is throttle position - when it is in that jumpy phase between working fine and not working at all, if I lift off the gas, the tach will come back. If I stand on the throttle, it will shut off. This seems to be very repeatable.

This seems to me to be a failing crank sensor or something, but there is no change in how the car drives. I know there are two crank sensors on the EG33 - is one of them dedicated to the tach? Any other things that could cause this?

Re: Intermittent tachometer
 

Figured I'd bump this up again, as I haven't solved it yet and haven't been able to get ahold of any sensors to swap out without paying a ridiculous amount of money. Not against spending money on the car, but it would be nice to know for sure if a CPS was the problem first.

If it makes any difference, wiggling the connectors and bumping the sensors doesn't make a difference. Next step is to pull the connector to see if I can replicate the problem, but it is supposed to be -5 tomorrow morning, so that will have to wait a bit...

Re: Intermittent tachometer
 

Hi the tach runs on a made up signal from the ECM ,it shares power with the fuel meter and other things in the combo meter
you might want to check the screws on the back of the meter ,just up plugging and reconnecting may fix your concern ,

Re: Intermittent tachometer
 

Did it fix your problem as I am also having this problem but mine is a 92.

Re: Intermittent tachometer
 

Mine is also a '92, and I haven't had any more time to mess with it yet. Drove ~2 hours to Cincinnati last weekend and the tach dropped out on the way there after 30 minutes. It was fine the whole way back, so who knows. Driving ~2.5 hours this weekend, and I'll see if it does it then. I can't really try messing with anything unless it stops working, is the problem. I'll check the connections at the ECM and the cluster, but given that it never, ever happens when the car is cold, it seems like the failure mode doesn't match.