I got a 91 hatch with a b16a swap, 5 speed.

When I bought it it had a pro comp 10k autometer tach and I noticed that sometimes it doesnt match the factory one. Sometimes its right on the money and other times I can burry the factory at 8k and the autometer still at 7.5k. The factory always stays on 0 at idle too. I can see where the tach wire was tapped in on i guess the ignition coil? What could be causting this?

 

Anyone got any ideas?

 

your factory tach is at 0 at idle? because.. thats not supposed to happen.

My guess is the tach went out on your cluster, so the person before you bought an autometer. It is a good chance your autometer is correct, and your factory one is totally toast. You should probably ignore the factory tach.

The ecu gets the tach signal from the same place as the autometer, so your ecu should be seeing the rpm that is displayed on your autometer tach, despite your dash tach being jacked up.

 

But is it normal for my car to idle at 1.5k? Thats what the autometer says and it feels like its idle is at about 1k or 900.

 

the only tru way to find out is u need a rpm reader. i had a snap on timing light that also displayed RPM, came in handy when i got my std it doesnt come with a tach. look out in the market. u can find the pretty resonable.