DIYPNP MS2/e (96 1.8 suddenly goes lean and dies) - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-31-2015, 08:46 PM   #1
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Default DIYPNP MS2/e (96 1.8 suddenly goes lean and dies)

I have been having an issue where my car is idling perfect then if I turn on the a/c and it only does it sometimes my AFR's go very lean and the car dies until I cycle the key and it starts normally. I have not tuned AE yet. I did notice in my log that when this happened my TPS went as negative as 1.5%.

Some background on the car. (stock injectors, MAF in place, only thing ive added to ease tuning is a AEM Uego wideband). Wideband receiving power from db15 12v with an inline 10a fuse and grounded through the db15 ground.

Attached to this post is a view of my log (uploading Security token issue, pic for now) where this happens several times and you can see a spike in AFR's and drop in RPM's. Any insight would be greatly appreciated.
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DIYPNP MS2/e (96 1.8 suddenly goes lean and dies)-graph.png  
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File Type: msl highway.msl (1.80 MB, 67 views)

Last edited by el maestro; 06-03-2015 at 12:04 PM. Reason: added log file
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Old 06-01-2015, 01:43 AM   #2
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Heres another screenshot
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DIYPNP MS2/e (96 1.8 suddenly goes lean and dies)-graph.png  
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Old 06-02-2015, 11:23 PM   #3
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Anybody?
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Old 06-03-2015, 01:53 AM   #4
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tune the car? you got ac idle up and all that stuff that's likely not tuned to add more fuel with extra load at idle, also ego correction is off so it's not adding more fuel, and I bet your ve map doesn't even have more fuel above the idle ve cells

and that's just looking at that screen shot
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Old 06-03-2015, 11:45 AM   #5
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The second screenshot is my main concern. I have added more fuel to the idle cells in order to compensate for the a/c. After more running the car it doesn't matter that the a/c is on when it goes into this lean condition.

I have noticed however that it does this when the car is warm. My afr's peg lean and then the car starts to run like shiet until it dies. I did notice that when this does happen the engine does not die right away it will idle like **** for a minute then die. Cycling the ignition switch reliefs it enough to start again but shortly it will do the same thing. Letting the car cool seems to be the only way to space out these lean events.

Hope that gives a little more insight.

Thanks for the reply 18 psi
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Old 06-03-2015, 11:50 AM   #6
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you need more fuel above the idle cells if your map goes up when you engage ac
also you need to figure out why its leaning out. is the ait heat soaking? is it pulling fuel as a result?
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Old 06-03-2015, 11:56 AM   #7
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The temps at the iat/maf seem fine. I have added more fuel to those cells and it helps short term but this is only intermittent so when its running fine the adding more fuel just makes it pig rich and when this event pegging lean happens I can keep adding fuel and it still will go lean and die.

Any suggestions on preventing heat soaking the iat?
This log is before I did that.


Will ADD fuel above the idle cells and report back.
Attached Files
File Type: msl highway.msl (1.80 MB, 71 views)

Last edited by el maestro; 06-03-2015 at 12:14 PM.
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Old 06-03-2015, 11:59 AM   #8
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I also have tried with EGO on/off. Makes no difference
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Old 06-10-2015, 01:36 PM   #9
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So the issue is only present now when the laptop is connected to the ecu intermittently. Otherwise I have dialed the car in and it runs perfect.
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Old 06-22-2015, 04:54 PM   #10
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After doing more research on communication errors I purchased a 3 foot usb to serial cable and still had issues, I purchased a FTDI converter with no cable on amazon for $12 and running a 6 foot serial cable directly connected to it and have had no issues with the car intermittently going lean when connected. Problem fixed just wanted to report back in case someone else is running into this issue.

The only thing I notice now is that when data logging or high load while connected the tuner studios software will freeze momentarily multiple times while tuning but only under high load. This sounds like a noise issue but some opinions would be appreciated, thanks bitches.
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Old 06-23-2015, 12:29 PM   #11
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Got a data log of the freezing you can post?
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Old 06-24-2015, 01:44 AM   #12
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Here is a log of when Tuner studios froze momentarily while doing a WOT pull/mixed with some highway driving. I am actually running a 10 ft serial cable which might be the issue. I just purchased a straight thru 6 ft serial cable in hopes of curing this problem. Only issues I have had thus far have been comm related everything else has been great.

It is a learning curve but ya gotta learn somehow, plus I started off with this terrible 6 ft usb to serial cable that would constantly have issues.

Im sure something is still off(tuning side) but its the best Ive got so far. Car runs great though. Ordered the sequential inj module so hopefully that makes getting a smoother idle easier although besides MAT heat soak in this incredibly AFRICA HOT my CLI idle is pretty spot on. I have semi fixed this issue playing with the air density table. (STOCK MAF in place)
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File Type: msl 2015-06-21_18.10.26.msl (1.58 MB, 67 views)
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