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Hey guys, new to the forum here looking for some LNF help. I actually have a DF Goblin kit car built from a 2009 SS/TC - GMS2 sensors, ZZP tuned 18-20psi boost on 93 octane. Recently started having an issue with power loss and sputtering once boost hits 10-15 psi and I’m stuck looking for help (link to video For reference
) . Here’s some background on what started.

One day the it started seemingly out of the blue during a pull it started doing the sputtering - came to find Shortly after the air/water intercooler had run dry (potentially unrelated). Fixed that, changed spark plugs and coil packs. No DTC’s. Found a few boost leaks which were fixed. Didn’t have any effect on the issue. Hooked in an AEM wideband AFR gauge, just monitoring by eye during WOT pulls looks to stay at 13-14 Which seems a little lean but not enough to cause the sputter. Compression tested all cylinders dry/cold..

Cyl 1 - 160
Cyl 2 - 135
Cyl 3 - 70
Cyl 4 - 160

After a splash of oil into the cylinders.
Cyl 1 - 185
Cyl 2 - 195
Cyl 3 - 170
Cyl 4 - 170

This points toward some piston ring wear in a few cylinders, so we did a make- shift leak down tester to confirm that cylinder 3 bleeds 90psi -0 over about 5 seconds. The others bleed over 12-15 seconds. This still doesn’t seem like enough to cause the sputter and loss of power.

Ive also check via scan tool that the TPS seems functional and smooth from 0-100% throttle. Fuel rail pressure under WOT seems to hover 1500-2000psi.

The weirdest part is the issue seemingly “disappeared” for about 30min last week and then came right back. I just got HPTuners in today so hoping I might be able to log something that would help here. If anybody has suggestions it’s very much appreciated!
 

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Discussion Starter #2

Here’s from about 30 min before the last video- when I took the car out looking to get a video of the issue, and instead got a video of how we’re suppose to be running
 

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I think I may have seen this on cobaltss.net. but it looks like cyl. 3 is about shot. have you done a leak down test to see why compression was so low dry? that will probably tell you exactly what need to be replaced.
 

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So I see the compression is not great. Do you have a scanner that can see what the MAP sensor is doing. Just comes to mind that I’ve seen similar problems with them, on various vehicles. And maybe half of the time there is no code, but the readings will be off. I dunno it’s worth a look since it comes and goes.
 
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