tach issues

[jchamber22]

Hey- I'm new to the 300zx community and new to this forum. I tried to search this issue and found someone who had the exact same problem but did not list the fix or if they even found a fix.

The tach shows 0 when the car is off. jumps into the 2700-2800 range when you crank and run. It stays around there with almost no movement until you get high into the RPM range and then it drops back to 0. It remains at zero until you shift or back off the throttle.

Any help would be greatly appreciated!!

[twinturbozxtacy]

sounds like a ground to me, or something is connected wrong. it happens as the plugs for the o2 and coils are the same. i had a dismantled harness and wouldnt you know it they were in the wrong place. just a thought...

[jchamber22]

Thanks for the reply! Will check that out tomorrow. If the connections are reversed as you suggest, wouldn't that cause the car to run poorly?

[twinturbozxtacy]

in my case it was more than poorly, yours might not be as severe, although to me i think its a bad ground. the connectors behind the dash are not similar to any others within the entire car, BUT i did have a turbo timer that somehow always made my speedometer read 10mph, even when the engine was off and i was sitting still with the ign on... it could really be anything, which is why i hate electrics.

[jchamber22]

Ok, well I'll check it out tomorrow and post my findings