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3rd bad coil pack in 1 week or less

Old 04-23-2019, 09:42 PM
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Default 3rd bad coil pack in 1 week or less

3 bad coil packs in 1 week (and counting)!!!!!!! Always the cylinder 1&4 coilpack. Would unseen damage to a spark plug wire be the cause to this?
Or could it be more likely a bad spark plug? ps I have tried to fix grounds. I also have Poly engine+diff mounts, and a exhaust that lays right on the tranny tunnel. Could vibration destroy the internal ignitors that fast?

Short but Detailed explanation:
Brand new plug wires, coilpack less than 1,500miles ago.

3months ago Redid interior dashboard, After re installation of dash, noticed tachometer stopped working. Oh well /me shruggs

5 days ago misfire occurred upon startup one day. After running great up 'til. Timing light indicates cylinders #1 & 4 had no spark.

new coil pack installed, started car up. Idles good, all 4 cylinders sparking, turned off.

Next day start up and misfire is back. Cylinders 1&4 no spark again!

cleaned 2 grounds, tightened the bolts (behind cylinder head & in front of intake manifold near TPS) Installed another new coil pack.

disassembled part of the wiring harness specific to the coil pack connectors (power[blue],ground[black],signal trigger[brown+yellow],tach[black+white] '94-95) and upon inspection found poorly spliced wires for the ground and power to the ignition packs. I also found some minor to somewhat severe razer blade cuts in the wiring. Redid the wiring. Soldered everything up good. New wiring in place of old bad wires, etc.

Start car up Sunday night, tachometer is working again! all 4 cylinders running, drove the car for 4-5 hours nice and good on Monday (yesterday). In boost, cruise, worked on the tune some yadayada. Engine/car was shut down and started back up SEVERAL times. several hot starts and cold starts, no driveability problems Got home, turned car off.

I lied, there was 1 small problem I noticed. The tachometer would wobble in a funny manner, except only between 3-4K RPM depending on which gear I was driving in. Otherwise it functioned normally. A little bit of research says this may be an indication of misfire. :/ (except it only was visible on the car's dash, not on tunerstudio)

This morning upon getting ready to leave for work, cylinders 1&4 once again, no spark. =(

Whatttttt couuullldddd thiiiissss beee

Thank you to anyone who knows

Running NGK bkr7es. They are a little over a year old now except with maybe only 3,400 miles or less. (This has been a jack-stand'ced Miata yup) I checked the gap today and still within rough spec of how they came from advanced auto parts. Same gap between all 4 plugs.

The plug wires are the usual NGK brand ones that a lot of people run. Less than 1.5k miles on em. However, I did pull them out a fair amount of times since then with how much I work on this car... Could it be that a bad plug wire keeps burning up these brand new coilpacks a day later after first start?

Last edited by NASSEX; 04-23-2019 at 10:10 PM.
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Old 04-23-2019, 10:35 PM
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Do load or RPM based misfires cause coilpacks to burn up that fast?

Sorry for the lengthy boring repetitive troubleshooting process post, it's just that I find it so odd how it only goes bad by the time I turn the car off, let it sit over night, and then start up the next day. Shouldn't that indicate something to some of you more knowledgable folk, that I'm not able to grasp? I'm stumped.

Last edited by NASSEX; 04-23-2019 at 11:13 PM.
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Old 04-24-2019, 07:50 AM
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Quick question regarding your tachometer. Do you have a resistor in the diagnostic box jumped for the tachometer to work? I am not familiar with the 94+ but on my 1990 I had to use one when I went to MS. Possibly a loose connection there if so?

In terms of your coil pack burning up, have you adjusted any dwell times in tunerstudio? I would also do a complete harness check. Set a mutlimeter to Resistance/Continuity (it also helps if the DMM has an audible beep noise for continuity) and start at the coils then work your way back to the ECU. You'll want to put your leads on both wires into the coil that specifically fire 1/4. This will determine if there is an intermittent short you haven't found.

Do you have any Miata friends close by that you could try your coil packs on their cars? Have you noticed any cracking on the coil pack itself? You mentioned you checked grounds for the coil packs but have you checked all grounds, even the one at the PPF?
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