MSIIDIY 1.6 Initial Start up sounds like a WRX - Misfire?
 

Hi Guys,

I am literally in the home stretch on getting my Miata back on the road. I managed to get most of the bugs ironed except for this last one (hopefully). I can start the car up fine, however it sounds like it's mis-firing yet very subtle. Its acoustic tone resembles a WRX, if that paints a clearer picture.

What's wrong? I've captured a log during the initial start up in hopes someone with a keen sense can identify what I screwed up.

Probably a misfire. All misfire issues I've had have been ignition. What coils do you use and how old are they? What year is your Miata? How old are the spark plugs?

Pull the plugs and look for the wet one.

I am using the stock NA coils and they have been tested good prior to installing the MS. I have a 91. The spark plugs have less than 1,000 miles.

Pu da prugs. Loo fo da wet wun.

Hey Guys,

So I managed to do a few more things to help pin point my issue. Thanks for the suggestings about pulling my plugs. I pulled the plugs after a minute at idle. The outcome:
1-dry
2-wet
3-dry
4-wet

Then i checked each spark plug to ensure it's working, by grounding each plug to the valve cover and had my brother crank it over. All four plugs fired off.

After I ruled out any spark issues, I went to check compression on all 4 cylinder. 175psi on all 4 cylinders.

So, with all this information I strongly feel it may be my tune or my timing. Any suggestions? I've attached my tune to the first post if anyone would graciously take a quick look... =)

Post MSQ

Without any knowledge of your MS build. Or tune.

You have it set up in sequential mode for fuel. But its wired for batch. Or the other way around.

Or you have something weird in yoursetup.

What fuel injection harness. How did you build your MS.

Wild random ass guess.

I think i jumped the gun on this one. I forgot to test the injectors with a test light. so, injectors 1 and 3 doesnt fire off. injectors 2 and 4 fires off, which correlates with spark plugs 2 and 4 being wet.

I'll chase my wire for injector bank 1 and 3. Maybe its a broken connection???? i'll report back shortly.

Post your msq.

Are you using megatune, and all the other old outdated crap?

Here's more information:
- 1991 1.6 LNC NA RED, 5SP 2001 LSD
- Garret GT2560R
- Ebay intercooler
- 3" Turboback (open to atmosphere) with Electric diverter valve to stock exhaust
- ACT clutch/pp with OEM FW
- 460cc Rx7 Fuel Injectors (just cleaned, tested, flow matched)
- AEM WB LS1 Bosch
- Stock ignition
- New wires and plugs
- 175psi across all cylinders
- MBC

I purchased and built a MS2 V3 DIY kit. I've made my own jumper harness to integrate with the existing harness in the vehicle. I've also added a VTPS, AIT and Antilag.

I am using Tunerstudio MS Lite, V2.6.19

My MSQ attached. hope this helps. I'm presently armed with a multimeter testing the 1 and 3 injector banks.

One of your injector banks isn't working.

A 91 miata is batch fuel injection. Injectors 1 and 3 are wired together, and so are 2 and 4.

Somewhere in all of your stuff you didn't hook up the injector drivers correctly.

Looking at your MSQ you are setup correctly, so its either a hardware issue with the megasquirt or your wiring harness.

Couple ways to test this.

I suggest swapping the wires for injectors 1&3 and 2&4 at the wiring harness. Then trying again. If plugs 2&4 are now the dry ones and 1&3 are wet then it is an issue within the megasquirt.

You can also check continuity between the fuel injector plugs and your wiring harness.

Okay - pins 32/33 have continuity all the way to the injector plug. The plug also has continuity to ground. So, it appears I've ruled out that it's a wiring issue.... Sigh!

Megasquirt issue.

How is your wiring harness hooked up?

I pulled the female connector from another dead ecu. I used this piece and soldered it up to the db39 port and matched pin to ecu port accordingly.

Do you know where on the board I should focus for injector banks 1 and 3?

I want to know how you hooked the ecu connector to the db39.
I would scope the output of the injector driver. then the input. And see if the driver was dead.

@Ben and @Matt Cramer can be of help.

Thanks for the help. I've attached my mapping.

Do you have a Californian Miata?

Thought that started in 93?

Why do you have both pins listed for the injector. Why is 34/35 listed.

Yes, I have a California car... although I am not too certain if the hood was changed out during its previous lifetime. I know I have only 1 cat and 1 o2 sensor.


I have tested my injector circuits and everything checks out fine. I ground pins 21/22 on the U1 socket and inj1 and inj2 LED turns on. I am so lost...
I referenced this site to help troubleshoot the injector driver circuit:
http://www.diyautotune.com/tech_arti...leshooting.htm

That is precisely it. 2 wires coming out of pins 34 and 35 bridged together by solder and connecting to the according injector pin.

Why do you have both 34 and 35 connected to the injector wire?

Because pins 34/35 drive injectors 2/4 (bank 2, in batch fire mode)

I did the same thing with pins 32/33 for injectors 1/3. (Bank 1, in batch fire mode)

makes sense. Different than ms3. But I've never played with ms2.

Did you try swaping the wires around and seeing if the wet cylinders switch?

Outcome: I switch bank1/bank2 on my harness and the misfire did not go away. However, there were no wet plugs. Injector 2 and 4 did have more black soot than 1 and 3 but all plugs did remain dry.

The misfire note seems a bit closer and smoother now. The revs are peppier. I wonder if my copper plugs are done from all the fouling and such.

I am now stuck between a rock and a hard place....

Did you put new plugs in?

I bought a fresh set of BKR7E's and that did not help at all. I confirmed after that 2 of the 4 injectors are not firing.

I'll test for continuity again from the MS harness to the injector harness.:confused:

Which 2 arent firing. Stop doing random stuff and figure out which ones arent firing and why.

The ones that were dry when he checked the plugs, I'm guessing.

But he didnt swap the wiring and check again. Because that would narrow down the problem.

Right, and he should have.

Are you using output test mode to test this?

So I switched Inj1 and Inj2 with pins 32/33 and 34/35, basically swapped the banks. As expected, injector 2 & 4 stopped working which initially was 1 & 3.

As of right now, I checked for 12v on each lead on the 4 harness plugs and they checked out fine. I also checked continuity from the injector harness all the way to pins 32/33 and 34/35. Continuity as expected.

This leads me to the board. I have the MS on the bench hooked up to a Jimstim. I also have 2 injectors with the pigtails hooked up. The black wires is hooked up to constant 12v, and the green/white wires hooked up to injector bank 1 and 2 respectively.

Injector bank 2 is non responsive. This is my issue. What is weird tho, I tested the injector circuit by grounding pins 21 and 22 on U1 and the LED's for inj1 and inj2 turn on. Based on the link I provided above, this indicates the injector drivers are operational....

however, I don't think that is the case based on where I am at now.

I only read teh first post:

you messed up on your wiring and you probably only have 2 spark plugs or two injectors firing.

the LED circuits are for Spark, not injectors.


The injectors are run off the U4 IC. you probably should inspect how you build the board and see if youre not missing something on the injector circuits.

Thanks Braineak for your help. I appreciate it.

I am currently focusing on the U4 IC and all other components to ensure continuity and that certain voltage values are present in on/off conditions.

When I was referring to LED, I was referring to the JimStim LED's that are marked Inj1 and Inj2, not the LED on the MS.

For testing, I connected an injector to the JimStim to replicate what is on my car. I hooked up one end of the pigtail to 12v and the other to Inj1 and Inj2 terminal on the jimstim. The injectors pulse on inj1 terminal which is expected. When I connect to inj2 terminal, NOTHING - no response or clicking.

To my luck, I shorted something on the JimStim while connecting the Injector and now my C1 and F2 are shorted (assuming) because they both get hot as hell after a few seconds of the jimstim being on. Then after a few seconds, the jimstim stops powering the MS.

Thanks for the help again. My plan to address the short on my JimStim so I can continue troubleshooting the U4 IC.