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Old 08-30-2009, 06:43 PM   #1
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Talking Ign Stumble Update

After fighting with this stupid ign stumble, I think I got it fixed! Here is what I did before changing to CoPs.

1) New BKR6ES-11s gapped to .035 (hesitation went away quite a bit, still there)
2) Changed plugs again, this time to BKR7ES gapped to .030 (no noticeable change)
3) Changed the coil pack, stumble appeared to go away, then it came back in 10 miles.
4) Changed the exciter, did nothing.
5) re-installed stock ECU with Bipes, NO stumble :(

At this point I was quite frustrated, and the stumble would randomly come and go. The stumble was more prominent in the 4k rpm and up range. So following Braineak's write up on CoPs I installed a set off an ES300. And sure enough the stumble is gone! Car will now rev to red line while in 12 psi boost with no hesitation or stumble. I then purposely bogged the engine, no stumble, took it for a 10 mile cruise, no stumble. With any luck at all the stumble is now gone!

I am not sure what could have been causing the stumble. The only thing I did not change were the wires. But they have less than 10k on them, and I have never seen wires cause this issue.


CoPs being built
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CoPs in Miata
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Old 08-30-2009, 07:02 PM   #2
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Cool, we'll have to meet up again, your car sounds like it's a lot faster than last time!
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Old 08-30-2009, 07:54 PM   #3
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It is getting there.
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Old 08-31-2009, 02:35 PM   #4
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just effing shoot me, 30 miles later, on the way to work it started to stumble again. What the effing hell is going on, this is driving me insane.

Going to try two more fixes. First going to install some different injectors 440-470s, and remove the RRFPR. If that doesn't fix it then I am changing the CAS. Third if all else fails I will smash the megasquirt with a mallet and re-install the stock ECU.
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Old 08-31-2009, 02:41 PM   #5
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I remember something about the MS spark mods that cause a weak signal to the coil packs or some crap. The stock ECU not having that stumble triggered it in my head.
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Old 08-31-2009, 04:30 PM   #6
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May be time to do Joe's spark out mod....

I'm seriously considering it since I'm having all the same problems. I found four (seperate) COPS on ebay this weekend for killer prices and will install when they get in.

If that doesn't fix the problem it's between a new spark out or a big ******' hammer.

Good luck man...I'm counting on ya'.
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Old 09-03-2009, 01:57 PM   #7
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I think I have nailed it this time. So basic it is painful to admit.

When I installed my megasquirt I did NOT calibrate it to the CAS on the car.

So last night I re-installed my coil and wires, and hooked up my timing light. My CAS was set at 16* advance, and Braineak's timing map starts at 17*. So by following the instructions bellow, I discovered my Miata was running a full 6* advanced from what megasquirt saw. Basically 23* base timing, I am lucky I didn't hole a piston or bend a rod. Now the megasquirt is calibrated to the CAS, and SO far 40 miles later the hesitation is completely gone, and the car is running a little cooler now too

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Old 09-03-2009, 02:13 PM   #8
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Good news!

Glad the stumble is gone.
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Old 09-10-2009, 10:05 PM   #9
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hmm my friends car is going through the same probmlem, we checked for boost leak, maf ground, and replaced plugs with 7e's and gapped them to .30 and it still stumbles. Hes just runinng and emanage blue on stock ecu.
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Old 09-10-2009, 10:25 PM   #10
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If your friend is running over, say, 8 psi he might consider gapping a little narrower.

Brian - Glad you solved the problem, kudos for owning up to it here and braving the flames!
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