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Old 09-26-2013, 08:25 PM   #1
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Default MS3x + Shanghai S Misfire

Hey guys,

I am admittedly a noob at megasquirt tuning but I really thought that my car was running great lately. I had been breaking in my new clutch and the car pulled to ~7psi great (all that I pushed it to). The AFRs were stable and on target, and the car felt great after a little veanalyze autotuning. I drove the car for about 550 miles like this.

Now, when i pulled off the highway today i noticed the car started to stumble and run off the chart lean. I putted it with extremely light throttle for another 1/4 mile (under 30mph) and then pulled off the road.

here's my setup
1994 miata
braineak ms3x w/ AEM wideband
five-o 850cc ev14 miata injectors
intercooled shanghai S setup

I have attached a .msq and a log of starting my car in the driveway. I thought maybe it was an injector issue but I took a screwdriver to each and I did hear a discernible click on each.

Any advice or suggestions would be MUCH appreciated.
Attached Files
File Type: msl Misfiring log.msl (236.5 KB, 57 views)
File Type: msq Misfiring.msq (176.5 KB, 91 views)
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Old 09-26-2013, 09:49 PM   #2
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Spark plug gap is set to what?
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Old 09-27-2013, 08:30 AM   #3
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Quote:
Now, when i pulled off the highway today i noticed the car started to stumble and run off the chart lean.
this sounds more like the AIT correction curve needs to be tuned a little.
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Old 09-27-2013, 11:30 AM   #4
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Thanks for the replies guys,

Plug gap is set to 0.040"

In regards to the AIT tuning, I was thinking it might be something related to this but when I started the car cold this morning the engine was running leaner (14-15) than my usual (rather rich ~12:1 on cold start), and was still stumbling badly, something it never did when the AFRs were in that range before last night. The car also ran great every day for the last week and a half, from 100mph pulls on the highway to miles of stop and go DC traffic. It feels to me like there is an injector that is not working properly, but they are brand new.

Is there anything in a datalog that would show individual injector status, or that would indicate maybe a failing fuel pump?
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Old 09-27-2013, 01:27 PM   #5
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that log shows -4% fueling due to AITs, fwiw. that's not a whole lot, but would lean out a normally rich idle.

if you're sequential, it shouldn't be noticeable.

stock coils? what's your running dwell currently set to?
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Old 09-27-2013, 02:07 PM   #6
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Gap should be .025-.028 with stock coils.
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Old 09-27-2013, 02:39 PM   #7
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Quote:
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Gap should be .025-.028 with stock coils.
if it's breaking up in boost, yeah. But it shouldn't have issue at .040" at idle, where he's saying it's missing.
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Old 09-27-2013, 07:25 PM   #8
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The posted log is in warmup. It will help to see a log of it leaning out while clt > 180 F to exclude wue (or lack of wue).

Also, do ev14s have a deadtime of 1.20 ms?
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Old 09-27-2013, 10:27 PM   #9
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My 850cc Five-O EV14s have a 1.5ms at 13.2V. And they change dead-times with under-hood temperatures. The warmer it gets under the hood, the longer the dead-time. It's not AIT heatsoak either.
But mine are not running lean on cold startup - only whe thy get too warm/hot.
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Old 09-27-2013, 10:39 PM   #10
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Update: took the 850s out and swapped in a set of tan top 265 stock injectors, and the car now drives smoothly with no misfiring. Adjusted req fuel accordingly and left the dead time at 1.2ms. Going to RMA the injectors. Thanks for the help guys. I did the trick with the fuel pump and pressure regulator and found that the fuel pressure was right on the money.
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Old 09-28-2013, 10:47 AM   #11
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your MAT air density table is a bit extreme.
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