1994 Miata misfire (video inside) - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-20-2015, 06:34 PM   #1
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Default 1994 Miata misfire (video inside)

Stock Ecu, Mafs, injectors, etc

The car has done this since I owned it...... After sitting all night, when I start her up in the morning and start to drive her she will start to miss horribly just before becoming fully warmed up. She'll throw a tantrum for maybe 10-15 seconds and then she will idle/drive fine. The only other time she will start to miss out is when I give her more than 1/4 throttle..... The video doesn't show the cold miss since I had already driven her that day and she only does that after sitting over night. So far I've replaced:

Plugs NGK bkr7 @.025"
NGK blue wires
Coil packs
Swapped the CAS with one from a good running car
Checked/clean grounds in engine bay
fuel pressure gauge hooked up (pressure is steady during miss)
Wiggle all the wires/connectors
Check timing

The only codes the Ecu is throwing are for the egr and purge solenoids (previous owner removed and blocked off). I am curious if the stock Ecu will cut fuel if the Mafs reads too high of voltage or something???? From what I've read it doesn't. I have bigger injectors and an AEM but don't want to add those until I have a good running car with no issues.

Any ideas?


Last edited by nelson8708; 11-20-2015 at 06:48 PM.
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Old 11-20-2015, 09:26 PM   #2
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Long video is long. So - to clarify - you're running a turbo with how much boost with stock injectors and ECU?

Sounds to me like whoever built it sold off the ECU/Injectors separate.

Honestly to me, it looks like it's just running out of fuel.

Edit: just to say - looking at the video, 1:16, you're hitting 15:1 AFR just as you're building boost.

Stop driving. Seriously. You're probably killing the engine.

Last edited by gooflophaze; 11-21-2015 at 09:34 AM.
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Old 11-21-2015, 10:05 PM   #3
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All issues are happening out of boost. Seems like there are plenty of miatas out there running stock Ecu/injectors/mafs on 5ish psi and no issues..... I want to know why mine hits a wall before I even get into boost? Even more curious is why the car has a horrible miss for 10-15 seconds before becoming fully up to temperature......

I made/installed the turbo setup.... I'm not killing the engine yet, hard to do that while still showing vacuum on the gauge.
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Old 11-22-2015, 05:41 AM   #4
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At 3:20ish - you're showing 19:1AFR before you can hear the audible breakup.

Wire the wastegate open - Despite your gauge, I'm fairly certain you're building boost. Granted, it's been awhile since I've driven an NA car but the acceleration sounds boosted to me.
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