Need 90 Coil alternatives & Tach Info!

[DSM Jeff]

I have recently gone through my 2nd coil with in 2 months. A few months back my car was on the dyno and while in a run, the coil fried. It was replaced with a used one and I was on my way. I have recently replaced my engine and a week later while driving, the car fell on its face and felt like it wasn't running on all cylinders. Check engine light says Ignition Coil. Now the other thing I noticed was that the tach needle would bounce up as the rpm's increased. The needle wouldn't do a smooth sweep. I've noticed a 90 coil has a "tach interface" on it. I'm wondering if possibly this has gone bad. I've tried searching on how to test a 90 coil and I would have no idea on how to test the tach interface. I was told I could have blew another coil do to bad voltage. Well sadly I found after putting the new engine in, the charge back wire bolt loosend, so the wire was a bit loose giving me poor charging conditions. I fear that may have lead to another coil issue. I've tried another coil today, but used the same tach interface and wires, and the car will start and run fine. When i take it out onto the road and things heat, up, the car will once again have NO power. I just feels like it is not running on all cylinders. I'm running magnacore 10mm wires that are rather new. Brand new plugs that are properly gapped. My brother has a spare MSD DIS2 at home (i believe thats the model) He says it has a provision for a Tach signal in that.
My concern is how do I infact test and know that the coils themselves are bad. How can I test this Tach interface to see if that is bad (since the needle bounces) What are my options on putting in a better coil into a 90? Could a bad ignitor lead to problems. My ecu was tested and had the caps replaced less then a month ago. I'm either looking to buy a new oem coil, Try some type of MSD set up or go coil on plug, but with a 90 I can hardly find the info i'm Looking for.
any help or ideas or things to test would be greatly appreciated.
Jeff

 

[WhiteTsiAwd]

Anybody have anything to respond to this? I am having similar problems.

By the way, did you get it figured out?

Cody

 

[bfdahl]

I would try putting the coil on a buddies car and see how it runs (if you can) and determine if the coil is ok. I would switch plug wires too and put a OE set on or a set of NGKs.

there is a good possibility that you have alot of reisistance in your cars wirring harness.
are you familar with Ohms Law?

I have also heard of wirring harness issuse where they are routed incorrectly and cause similar problems to yours. AS i recall it had somthing to do with the wirring to the coil being too short or somthing. Try a search for this.

I was on the Evo forms the other day and a guy was having coil probs with his EVO coil on plug set up missfiring a high RPM and his FIX was to install a early 90s DSM coil!