Turbo 95 going EXTREMELY lean (23.8) under tip-in - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-09-2013, 01:27 AM   #1
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Default Turbo 95 going EXTREMELY lean (23.8) under tip-in

INFO about car:

95 Running MSPNP2
99 Swap
6 speed
BEGI S4 Turbo Kit (mostly) with GT2560
Innovate LC-1 with week old sensor.
Stock Coilpacks
Rather New NGK Wires
MSM Plugs with the stock gap (.040?)
550cc injectors - TLFPerformance - under warranty.
No MAF, only IAT.

Okay. As of Sunday I didn't have this issue. Nothing has changed in the engine bay or tune. I did a track day that day and by the end of the day I was having a tip-in stumble and some idling issues. It was very slight, but noticeable. I drove the car home fine with 0 issues.

Monday it got slightly worse.

Tuesday it got pretty bad.

Today was hardly driveable.

When I tip into the throttle, it will go lean for 5-6 seconds before it finally gets fuel and goes again. All other sensor readouts are normal: MAP, CLT, RPM, TPS, everything! There are no corresponding readouts that would cause this as a symptom. (To my knowledge)

Overrun Fuel cut makes no difference whether it is on or off.

My options so far are to

a.) test the fuel pressure - possible pump failure
b.) replace the fuel filter

These seem like an unlikely cause though, since it only happens at tip-in. If I haul *** in the car it still runs pretty damn good. AFRs are good too.

Screenshot:



LINK TO DATALOG>> CLICK HERE For some reason the upload fails every time I try to upload even though it is within the size constraints.
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Turbo 95 going EXTREMELY lean (23.8) under tip-in-problem2.jpg  
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Last edited by dhyde9; 05-09-2013 at 12:17 PM.
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Old 05-09-2013, 09:11 AM   #2
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get the log posted.
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Old 05-09-2013, 12:18 PM   #3
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Okay. The datalog is posted. It is hosted on Google drive, so just click the link and you can download it.

The upload fails every single time even though it is within the size limit.
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Old 05-09-2013, 03:20 PM   #4
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Wow! what a smooooth map reading. Looks like map sensor is very lazy, propably due to clogged, pinched vaccuum line or if you have an inline filter to this line , it is way too restrictive... Map readings usually are more responsive than tps readings. Your log shows the opposite.
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Old 05-09-2013, 03:33 PM   #5
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That would make sense. My gauge was reading fine but it is on a different vacuum port, so I will chase down the map sensor side after work tonight.
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Old 05-09-2013, 07:57 PM   #6
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Bingo! Awsome catch man!
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Old 05-09-2013, 09:08 PM   #7
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Always nice when its super simple fix
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