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Intermittent Fuel/Spark Issue - Need Help

Old 03-19-2014, 06:04 PM
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Default Intermittent Fuel/Spark Issue - Need Help - New Logs

Car is a 96 with a 00 stock motor. Running Brain built DIYPNP, FIC 650's, 320lph fuel pump, AFPR, I/E/H, etc

Ever since a track day about 3 weeks ago, I've had this intermittent low throttle fuel/spark issue where all of a sudden the car sounds like a Subaru and AFR goes crazy. I went out for a drive today after replacing my spark plugs, and sure enough the issue is still there. See attached log - it starts almost immediately.

I'm getting to the end of the tests I can think of and I could really use some experienced help here. So far I have:

- Verified base fuel pressure @ 3bar
- Check plug wires/connections
- Test injectors with Megasquirt
- Replaced old fuel pump w/320lph
- Replaced plugs w/ BKR7E-11's @ .030

I don't want to keep fixing things that aren't broken and possibly add to the problem, but I'm concerned about my coil pack and possibly MS firmware (currently on 3.1.0).

Anyone have anything similar happen to them? Any help is greatly appreciated!

** LOG UPDATED 03/30 - STILL SHITTING THE BED **
Attached Files
File Type: msq
NA-Aggressive.msq (84.3 KB, 65 views)
File Type: msl
2014-03-30_10.49.00.msl (656.7 KB, 52 views)
File Type: msl
2014-03-30_10.42.11.msl (1.38 MB, 49 views)

Last edited by Ian; 03-31-2014 at 04:31 PM.
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Old 03-20-2014, 12:16 PM
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Forgot to attach the tune. See above
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Old 03-20-2014, 05:16 PM
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Dumb question but I need to ask... FIC650s are listed as low-impedance "peak and hold" style injectors. Do you have a peak and hold board or are you using resistors?
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Old 03-20-2014, 05:29 PM
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Not a dumb question, because I don't know the answer. Braineack built this for me, so he would have to answer that. I'll PM him
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Old 03-20-2014, 05:40 PM
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When you had him build it, did he ask what injectors you would be using? Did he give you a tune file that already had the injectors specs or did you have to set it up yourself?
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Old 03-20-2014, 06:46 PM
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Originally Posted by Chiburbian View Post
When you had him build it, did he ask what injectors you would be using? Did he give you a tune file that already had the injectors specs or did you have to set it up yourself?
Unfortunately I can't remember, and I don't have a record of it through email or PM's.

Is there an another way I can tell? I have detailed pics of the board I can check easily.
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Old 03-21-2014, 08:05 AM
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I'll have to look at the log when I'm home. Sounds like youre dropping a clyinder or 2, either spark or fuel. Log will show if the MS is doing it, otherwise could be the wiring/drivers.
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Old 03-21-2014, 08:36 PM
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Originally Posted by Braineack View Post
I'll have to look at the log when I'm home. Sounds like youre dropping a clyinder or 2, either spark or fuel. Log will show if the MS is doing it, otherwise could be the wiring/drivers.
Thanks Scott, I look forward to your response. Let me know what you need from me.
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Old 03-24-2014, 05:53 PM
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Originally Posted by Chiburbian View Post
Dumb question but I need to ask... FIC650s are listed as low-impedance "peak and hold" style injectors. Do you have a peak and hold board or are you using resistors?
Wait Chiburbian - My injectors are listed as high-z, not low-z:

650cc FIC Mazda Miata Fuel Injector Clinic Injector Set (High-Z)

"This injector set contains high impedance injectors matched to the saturated injector signal generated by this vehicle’s OEM ECU, OR is suitable for use with an aftermarket ECU made or set up for high impedance injectors."

Last edited by Ian; 03-27-2014 at 12:56 AM.
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Old 03-27-2014, 10:28 AM
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This one looks like it could use some more tuning on the VE and acceleration enrichments, but I didn't see much beyond that in the log.
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Old 03-27-2014, 12:09 PM
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Originally Posted by Matt Cramer View Post
This one looks like it could use some more tuning on the VE and acceleration enrichments, but I didn't see much beyond that in the log.
Matt, thank you for the response.

My VE table produces my target AFRs consistently. I will look more into the Accel Enrich settings, however those are what was provided by Braineack when I received the ECU and they never caused a problem before a month ago when this started happening. It doesn't make sense that the car ran well with those Accel settings, then all of sudden started acting like it's running on 2-3 cylinders at random every time I drive it. Wouldn't those setting produce repeatable bad results if they were the root issue? I will check your recommendations regardless and do more testing. Thanks again for the input.
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Old 03-27-2014, 02:05 PM
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Jesus. F'ing. Christ. I attached the wrong log previously. Update original post with a couple of my most current logs that show my issue. So sorry to all that have looked so far
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Old 03-28-2014, 09:55 AM
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The TPSdot seems to be triggering a bit too easily; you might want to raise its threshold. That's about all that jumped out at me. Maybe you could push the space bar when the problem happens to mark more clearly where things go wrong?
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Old 03-28-2014, 12:21 PM
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Originally Posted by Matt Cramer View Post
The TPSdot seems to be triggering a bit too easily; you might want to raise its threshold. That's about all that jumped out at me. Maybe you could push the space bar when the problem happens to mark more clearly where things go wrong?
Thanks again Matt! I will read up more on TPSDot and see if I can solve this.
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Old 03-28-2014, 05:28 PM
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I read up on AE here: MegaSquirt Acceleration Enrichment Tuning

Updated the TPSDot threshold to 45% up from 40% and drove the car for 40 minutes without a single problem! It looks like this single setting 5% difference was my issue, which is kind of crazy. I took out the ECU yesterday for pictures, so it's also possible that a connection was lose as well, but I can't be sure at this point.

Big thanks to Matt! PM'ing to buy you beer.
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Old 03-30-2014, 03:19 PM
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Spoke too soon. FML

See attached log on first post. Issue is present during pretty much the entire log.

AFR, TPS, everything is just going crazy. No idea what's going on...
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Old 03-31-2014, 04:02 PM
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Can you hit the space bar when the issue surfaces? That will make it easier for me to look up on a data log.
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Old 03-31-2014, 04:43 PM
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Matt, I am not able to mark the log after the run in TunerStudio, however it is present throughout the entire 2014-03-30_10.49.00 log.

I also uploaded the previous log, 2014-03-30_10.42.11 which shows the car running normally for a while then the issue happening 3/4 through at the 872900.0s mark.

I am logging myself while driving - sorry about forgetting to hit the space bar while managing everything else.
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Old 04-01-2014, 05:46 PM
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If you can get the issue happening consistently, would you be able to shut off the engine and use Output Test Mode to check to be sure both ignition channels are sparking?
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Old 04-01-2014, 06:40 PM
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I'll see if I can catch it. Is this the correct procedure and settings I should be using?

MS2/Extra - Output Test

Not really sure what I should expect if the test is successful or not.

Last edited by Ian; 04-01-2014 at 07:06 PM.
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