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Problem: hard shuttering/loss of power at boost


sportwagon

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So yesterday on the way into work I had a serious problem (at least it felt like one)...

 

I was accelerating in 5th up an incline and when I hit about 1.1 - 1.2 barr, the car violently jolted and stuttered... I immediatley let of the gas and due to work priorities I wasn't able to pull over and check out the car... I did hook up the AP and switched to economy mode and did a quick data log of the issue... which was happening at a much lower boost level ~ 8 psi by the time I was able to get a log... Anyway, I left the car at work and I am driving my wife's car... Attached is the log I took.

 

I have an 05 LGT sedan MT, with 99,000 miles Stage 2 with Cobb Stage 2 maps... I'll post up a full mods list if needed.

 

I've never done any tuning (only a tuning/data logging noob, not a full noob), but I did notice that there was no wastegate duty going on?

 

I'll attach another log I took a while back to give a reference of when things were working fine and dandy?

 

Can any of the gurus identify anything wrong from the limited data logging info provided? Please help!

 

Thanks,

sportwagon

02Feb10 data log - problem at boost.csv

Highway home from Thanksgiving 2009.csv

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catted dp... would a fuel cut feel so violent?

 

when I first hit boost cut, it felt to me as if I blew the engine...it is pretty violent; immediately afterwards I got a CEL and I was limited to 8-9 psi. I thought Boost cut always leads to CEL tho.

 

EDIT. Just read your whole post..when limited to 8-9psi, there was no stuttering or hesitation.

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No WDC is because you are running the eco map

 

 

That's what I thought might be the case!

 

 

So a boost leak might be the problem.... I was thinking more serious based on how it felt... I haven't driven the car, it's parked in the parking garage at my work, I got a ride home last night and drove my wife's car into work today!

 

I'll check the usual suspects for boost leaks tomorrow!

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I don't think a boost leak would have caused the problem. If anything, a boost leak would lead you to seeing less boost and the car would just run like crap. I still think you overboosted from going up an incline in 5th.

 

A leak in the air line to the wastegate actuator would cause the turbo to overboost.

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I don't think a boost leak would have caused the problem. If anything, a boost leak would lead you to seeing less boost and the car would just run like crap. I still think you overboosted from going up an incline in 5th.

 

 

What would be the consequences of an overboost?

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