Tachometer & check engine light issue

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Jun 16, 2025 | 09:34 PM

1028Bjs#

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Joined: Oct 2018

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From: Ohio

Tachometer & check engine light issue

I have a 89 RX-7 convertible with the 1.3L. Just recently the tachometer started to function sporadically. When the tachometer stops working, the check engine light comes on, but when the tachometer is working, the check engine light is off. The engine still runs regardless. I purchased and installed a used trailing coil pack (2 coils with igniter) and the problem is the same. I hooked up an inline spark plug tester on one of the trailing spark plug wires and when the tachometer stops working and the check engine light comes on, the trailing plugs don't fire. The individual trailing coils bench test ok. Any help and ideas are appreciated.

Jun 18, 2025 | 10:09 PM

ourx7510

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Joined: May 2012

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From: Norman

Not sure what is causing that.. my only suggestion is to make sure the mounting surface is clean between the coil and frame(no paint.ect). The coil gets it's earth/ground from the body.

Jul 3, 2025 | 05:09 PM

Brice_Brice

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Joined: Sep 2007

Posts: 316

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From: Montgomery, TX

Id start with the tach plug on the back of your gauge cluster and follow it. Where it connects you may find evidence to lead you to the next step. Maybe something electrical

Jul 20, 2025 | 05:05 PM

Raymond Cascella

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Joined: Mar 2018

Posts: 28

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From: Florida

If you pull the secondary coils there is a ground terminal on the strut tower. Clean and remove bolt that holds it to tower.also clean all the wire conections make shore bolt that connects to tower is grounded.