ecm and factory tach

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Apr 22, 2009 | 11:30 AM

3rdgengmachine

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Joined: May 2004

Posts: 180

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From: Inez kentucky

Car: 87 iroc z

Engine: 358 tpi

Transmission: 700r4 with transpack

Axle/Gears: 3.42 with powertrax

ecm and factory tach

does anyone know on the 87 maf type tpi if the ecm needs the factory tach hooked up or does the ecm read rpm internally???I hooked up an aftermaket tach and left my factory one unhooked and was wondering if i should hook it back up or not.Also i have the autogage autometer tach and it seems to be reading to low has anyone had to use that adapter and it made it read right id hate to spend 40 bucks and find out i just need to hook it to a differant place or something i have an msd 6 ignition on it to and have the tach hooked to the spot on it

Last edited by 3rdgengmachine; Apr 22, 2009 at 11:34 AM.

Apr 22, 2009 | 08:16 PM

RBob

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From: Chasing Electrons

Car: check

Engine: check

Transmission: check

Re: ecm and factory tach

The ECM reads the RPM via the 4-wire connector to the ignition module. The tach comes off the coil-. So no problem with an aftermarket tach and leaving the stock tach disconnected.

RBob.