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Old 05-05-2014, 10:49 PM   #1
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SR SR20 Running Rich, Losing Boost

So I'm having an issue with my SR boosting and my AFR's are way rich under boost.

Here's my set-up:
1993 240SX Hatch
S13 Red Top SR (rebuilt, by me, 2k miles ago. Honed cylinders, re-ringed and cleaned stock pistons, machined, polished, and balanced crank, matched rod and main bearings, Tomei metal headgasket, ARP headstuds, head was decked and valve job done, new water and oil pumps)
Currently running stock turbo which was rebuilt about 4k miles ago, injectors, intake, MAF etc.
FMIC, 3in Catless exhaust, Walbro 255 in-tank, Innovate Wideband, Autometer Boost Gauge, NXT Boost Controller @ 14psi

I've scoured the interwebs on ever forum out there and can't find anyone that is having my same issue so I'm posting here hoping for help. I am a mechanic by trade but my own car has me pulling my hair out.

My issue:
When accelerating, my AFR's are around 9.8:1 and the car is very hesitant at about half throttle. If I lay into the throttle, the car will lean out slightly and boost to 14psi @ about 11:1 AFR. The boost hits 14psi, will hold for a few seconds under WOT then the car falls on its face and loses all boost but doesn't go lean or rich.. I've tested for boost leaks and none were found. I've wired the wastegate shut and regulated boost with throttle and the issue still persists. If I remove the boost controller and run off of wastegate pressure, the issue is still there. I've gapped my plugs down to .025 and replaced all coils and regrounded the coil harness.

I've tried everything that seems logical and I am out of answers. Any help would be much appreciated!

Thank you in advance.
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Old 05-05-2014, 10:59 PM   #2
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Have you check if your MAF is working properly?
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Old 05-05-2014, 11:06 PM   #3
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I haven't located a good one to swap it with yet but it appears to be functioning properly. I will try harder tolocate a known good part to swap it with asap
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Old 05-06-2014, 09:08 AM   #4
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Pull ecu codes. Clear codes. Start car, warm engine to operating temperature, put ecu into timing mode, verify timing....adjust.

Have you done all the usual, boost leak test, fuel pressure, injector leak test etc.

Sounds like the knock map to me, but it could be anything, resetting timing should get you back to normal for awhile, but the symptoms may come back.

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Old 05-06-2014, 11:39 AM   #5
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I've done all of the "standard" tests. I've checked for boost leaks, injector leaks, ohm tested all injectors and coils, tested spark output, checked all grounds, and checked all connections. I've changed spark plugs and pretty much ruled out the obvious. I will try the above mentioned procedure and post my results. Thank you!
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Old 05-08-2014, 08:17 PM   #6
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Okay, so here it is:
Pulled codes from the ECU and came up with code 34, knock sensor. Cleared codes, replaced knock sensor, problem solved!

Thank you so much for your help, didn't think a knock sensor would cause my symptoms but I've been proven wrong lol
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