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Old 04-24-2011, 07:54 PM   #1
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Default Car behaving like it's hitting boost cut, but limit already raised?

Hi all,

I finally got round to fitting all my turbo gear over the past two days, and managed to take it out for a spin.

Around 8psi (actuator pressure) I hit a brick wall and the car seems to shut down all power and the car bucks erratically. If I ease off the accelerator it goes back to normal.

What I've described seems to be typical of a boost limit cut right? Only I've already raised this in megatune to a stupid high figure which I'm unlikely to hit (300kpa).

Can anyone enlighten me on what's going on? Are my spark plugs at fault? I didn't think that spark blowout would behave like this.

I've attached my MSQ and log of the problem. Ignore the shitty AFR's at the moment! I only got up and running tonight, so they're a little rich right now.

Attached Files
File Type: msq 7.msq (35.0 KB, 51 views)
File Type: xls 7.xls (258.4 KB, 41 views)

Last edited by GrahamC; 04-24-2011 at 08:01 PM. Reason: Added print screen
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Old 04-24-2011, 08:05 PM   #2
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looks like you have some grounding issues. those are resets and your CLT temps are spiking down like crazy.
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Old 04-24-2011, 08:20 PM   #3
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Sounds plausible, but why would this only happen under WOT and ~8psi? I can replicate that fault every time under the same situation.
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Old 04-26-2011, 12:12 PM   #4
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I've ordered new spark plugs today, but while I wait for them to arrive, how would I go about checking the grounds?

So far I've noticed there is an earth strap from the back of the engine block to the chassis on the UK driver side (US passenger side). I'm also aware of a grounding point underneath the throttle body.

What exactly do I need to do? It looks like I can replace the rear strap with a new thick gauge wire and new connections, but what should I do with the one under the throttle body?

Where else should I check for faulty ground connections?
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Old 04-26-2011, 12:16 PM   #5
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gap the new plugs to .030" and see what happens. a lot time ago (cira 2007), I rmeember having this issue when I was having spark blowout...the logs would show hard resets everytime I hit around 7psi or so. Swapped plugs and wires and the the issue was resolved.
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Old 04-26-2011, 12:40 PM   #6
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Will do mate. Fingers crossed this solves the problem.
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Old 04-26-2011, 12:50 PM   #7
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Definitelylooks electrical, but good reminder to grab a new fuel filter if you're still on the original.
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Old 04-26-2011, 02:43 PM   #8
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Problem mother ******* FIXED

Pulled the spark plugs tonight to check the gap and they were about 0.45

Re-gapped them to 0.25 and the problem has gone.
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Old 04-26-2011, 03:08 PM   #9
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great!
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Old 04-26-2011, 04:58 PM   #10
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This happened once when i forgot to plug my IAT back in after doing some work to the piping.

glad to hear you fixed it!
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Old 07-15-2011, 03:25 PM   #11
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Just picked mine up and it's acting like the OP described

Gonna try pull the plugs and check em
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Old 07-16-2011, 01:16 PM   #12
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Recommended plugs and wires?
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Old 07-26-2011, 09:50 AM   #13
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Replaced the plugs and wires

gapped at .044 and boost cutout is gone here as well

I tried gapped at .028 and was getting detonation on partial throttle
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