1993z32

After 20+ hours troubleshooting and talking to some experts on the topic, I need to see what you guys think. Prepare for TL;DR material.

My setup:
1.6L turbo @ 14.5psi / 236whp / MS2PnP / 750cc / 340LPH / E85 / 202k

Original issue:
Misfiring or blowing out spark and jumpy tach with stock ignition, worse at peak boost and over 5000RPM, nonexistent below 10psi. Running new BKR7E and have run the gaps from 0.030" down to 0.022" with minimal difference. New NGK blues, have tried dwell at 3.0 and 4.0 with no difference. Identical misfire on 91 octane and E85, AFR 11.6-11.8 @ WOT, base timing verified in MS.

Video of car misfiring on stock ignition (tach drop between shifts is due to flatshift, observe jumpy tach during acceleration, noticeable power loss at each misfire)
Inside car: Exhaust clip (start at 20s):
So I figured it was time to upgrade the ignition. Products purchased: New OEM LS Truck coils and new OEM coil harness, as well as GM spark plug terminals + MSD boots. After not having luck running sequential ignition, I decided to wire it up in the stock wasted configuration with the stock trigger wires, 12v (blue wire from igniter harness), and ground, as well as grounding to the head. The car would lose all power at 10psi. And after gapping from 0.024 to 0.045, it loses all power at 5psi. Everything below 5psi is fine, I can literally run 4psi all the way to redline. I pulled off and sanded every ground on the whole car, as well as checking 12v and ground at each coil, even at full throttle, with a DMM. Thinking I may have messed up with the new terminals on the spark plug wires, I put new wires on with the original Mazda terminals, crimped down to the GM size with a tight fit. Same problem still exists. I've tried dwell from 1.8 to 4.5ms with no change. It's not overboost protection either. The last thing I did was swap back to the stock ignition to see if it was another problem. It runs just like it did on the stock ignition before, 14.5psi with a random miss here and there.

Video of boost gauge with LS coils installed, when plug gap was 0.024 and loosing power at 10psi:
Anything else you guys can think of trying would be most appreciated.

sixshooter

iTrader: (12)

Are you still using the stock igniter with the LS coils or do you remove it and then add it back when you go back to stock coils?

1993z32

I removed the stock igniter when the LS coils were installed. Everything is now back to stock, including the igniter.

sixshooter

iTrader: (12)

Are you using a capacitor?

deezums

iTrader: (3)

To get your tach to work splice black/white with blue/yellow, if you wanted you could do that around the stock ignitor as well.

Can you take a photo of the contact pins of the harness side coil connector? Curly ran into a problem with cheap contacts a while ago, if I'm not mistaken.

You tied both ground pins on each coil together, right?

I am not using a capacitor, only because I didn't have one and am impatient.

I'm the guy from the video comments section

1993z32

I do not have a capacitor in place. Most of the write-ups I saw listed it as "optional" so I figured I could get by without it, or at least it wouldn't cause a major handicap like I have now. Cheap coil connector? What was his solution? I am using a new OEM GM harness. Yes both grounds are tied together. Nice to meet you deezums! (Again, haha.)

deezums

iTrader: (3)

Check from this post down, there are different GM coil contacts even though the plug is the same, or I think that was the consensus.

https://www.miataturbo.net/diy-turbo...4/#post1198883

bmxfuel007

iTrader: (21)

I had the same problem until I re-made my plug wires. I too had original miata wires that I had modified the end that plugged into the coil. Part of it was that I think the coil side connection wasn't on the pin (not the best design in my opinion), and the stock wire was a bit thin/loose in the angled boot and it would vibrate around and come loose. I'd only have misfires up top when in boost

Whenever I plug in the boot on the ignition side when I have to take stuff apart, I have to really make sure that the wire completely goes into the coil, with the round metal contact seating on the coil's pin. Your plug wires might even be a little bit short (especially plug #1) and could be arcing to the pin if it's not seated right on it.

In my logs when I'd get the misfire, my voltage would actually drop because the connection was bad and resistance as quite high, dropping my battery voltage to around 13v when normal running voltage was around 13.5-6

1993z32

^ Exactly why I tried two different sets of wires, one with the Miata ends crimped down, and one with the actual GM terminals which have a very distinct "click" when they go onto the coil. I still am slightly suspicious of the wire connection though, as my symptoms would definitely be occurring if the spark was either finding an easier route or having to arc over to the terminal. Now that I know everything is running fine on the stock ignition, I'm going to get the LS coils wired up again and continue troubleshooting.

bcrx7

iTrader: (5)

Most likely not the issue but good to try: have you tried turning anything that plays with ignition off, eg the flatshift? I wonder if it acts the same without it.

1993z32

I've tried running with every ignition cut feature off, no luck.

92turbomiata

I had an issue like this back when I was running BKr7e plugs, even at small gaps it would misfire. I tried several different things and nothing helped. One day I decided to try different plugs at a colder heat range for ***** and giggles and also because I had higher compression, thought since maybe it was pre igniting from the higher combustion chamber temps even on e85. I installed NGK 9 heat range resistorless plugs (#5238) and the issue went away. However I have recently gone back to BKr7e plugs and it's still fine so I'm not sure if that was the original issue or not. Worth a try though. The 7 heat range racing plugs is part number 4091. Cheap and easy thing to try at least.

JacksonRacingEngines

I was about to start a new thread but I saw this.

My set up forged internal 1.8/gt3071r/1000cc injectors/mspnp2

also having what seems to be an identical problem...

when running toyota coil on plugs with capacitor wired in and ngk heat range 7 plugs at .025 I Get a violent missfire under boost "15 psi"

Turned out i had a bad ignition coil driver in the ecu.

Matt fixed it.

worked great for one month and now the issue is back.

Ran some test on the coil drivers and they are perfect.

So i decided to wire up a set of gm Ls2 truck coils with the heat sink.

Still missfiring.

i may try wiring the 12+ to the alternator and wiring in a capacitor on the power and two small capacitors on the triger wires.

Anyone else have other ideas?

LS2 coils missing

toyota coils missing

JacksonRacingEngines

I made some wiring changes to try and fix the problem but with no luck.

I used the factory ignition harness blue 12+ as well as the blue 12+ up by the driver side head light. i soldered both power sources into my ignition coils. "gotta have enough power from that."

then the I added another ground that goes from the firewall straight to the bolt i have going into the intake manifold to ground the coils. "so basically it was double grounded..."

again no change.

next step may be to run the signal ground back to the ECU and put a CAP on the power wires. but my toyota COP have the CAP and they still misfire...

I hate cars i need a new hobby like knitting...

curly

iTrader: (25)

My solution was a used harness off eBay to get the right plugs.

I could replicate the problem fairly easily by wiggling the cheap eBay connectors. That doesn't sound like your issue.

Fwiw, I run stock magnacore wires for a Miata.

deezums

iTrader: (3)

1999z3 said he fixed his problem with new LS2 truck coils.

You really need OEM, no matter how many miles on them. It seems there are OEM replacements in circulation that suck hardcore, both coils and plugs.

JacksonRacingEngines

I am actually running OEM LS2 coils with the heat sink, I got them right off the truck at pull a part, I also am running OEM GM connectors as well " not saying that the connectors are not the problem" but it seems fishy that it is also happening with my Toyota COP set up as well.

Last time I had this issue the coil driver in my megasquirt was shorted out and eventually failed. once it failed only cylinder 2 and 3 were firing because the coil driver for 1 and 4 is the one that failed.

However I ran the test on the coil driver " set ignition setting to going high and cycle the ignition" MAKE SURE COILS ARE DISCONNECTED

most likely because it will burn up your coils. i dont know iv always just disconnected them...

after you have cycled the key you can plug a paper clip into the 12+ and the trigger wire for cylinder 1 and 4 and check voltage. Should be 4.9-5 volts.

Next do the same for 2 and 3. again should be 4.9-5 volts

if its something like 1 volt you know there is a problem with a coil driver.

however this time my coil driver was perfectly fine.

DO NOT FORGET to change your ignition settings to going low and cycle the key before plugging your coils back in.

and my ls2 coils seem to have enough spark, I can hold a plug wire a good 5 inches away from my fire wall and it will still arc to the firewall!!! these things are crazy!

Sadly they don't stop this misfire.

Im so tempted to sell my engine and set up and plop a 5.3 truck motor in it with a rear mounted turbo set up.

JacksonRacingEngines

This may sound crazy but with my toyota coil on plugs my car was missfireing on my way home from work under 10+ psi of boost.

Matt from DIY Autotune asked me to take a Data Log and a Composite log and send them to him.

So I stopped at my house to get my lap top and plugged in the usb and opened tuner studio, clicked Control+L and floored it.

No misfire at all.

It defiantly seems to be a computer issue, as i had driven the car home from work with the misfire and then 15 minutes later with the lap top plugged in its gone.

however tuner studio goes offline every time i do a pull with ve-analyse on or if I have the data logger on.

He recommends I purchase his serial to usb adapter instead of the DYNEX one I currently have. due to the fact that mine potentially is picking up noise.

deezums

iTrader: (3)

Do you get any lost sync hits while you are running tunerstudio?

Prolific adapters and drivers? I get the same thing, but just random lost syncs when it ***** up a write or something. If I close tunerstudio without turning off the megasqirt the drivers lock up and freeze TS...

I don't see how you could possibly have misfires with no laptop, then no misfires when the laptop is plugged in but not connected or logging. Maybe I misunderstand, but that makes no sense.

JacksonRacingEngines

Not sure if its a lost sync but Tuner studio will freeze so i have to unplug my usbto serial from the lap top and replug it in.

After I do that it gives me two ve tables to choose from one thats on TS and the other from the MS.

And yes i was driving home from work and the car had misfires when it would go into boost, i plugged in my computer with tuner studio and took a log and the engine ran perfectly smooth all the way up to the rev limiter at full throttle. however tuner studio still freezes.

I then unplugged the lap top after saving the logs and the car is still not misfiring like it did in the video, every once in a while it will have a hickup under boost but i believe that is because i cant really tune the top end since it keeps freezing tuner studio.

Iv been manually changing the values in my VE table to keep the afrs around 11.8 under boost.

It makes no sense that connecting the computer changes the misfire.

However i am sure the misfire will come back soon as last time it took a month for them to redevelop after having my coil driver repaired.

sorry if i am confusing you.

drive before hooking up lap top: Misfire

Hook up lap top and take data log "no other changes": misfire gone:

Currently no lap top hooked up: Only a small hiccup once in a wile under boost.

and yes a prolific serial to usb adapter.

I will purchase DIY autotunes adapter to hopefully stop TS from freezing.