[Cm452]

I've an 08 xi with the n54, and the engine's performance is all over the place. It seems, on the same tank of fuel, 93mron, that some days it will really pull hard, and some days it's just plain wheezy. A strong correlation seems to be adaptation: a long drive on the highway and it pulls like a train, but when the engine isn't good and hot (and/or I've been tootling around town) it's downright anemic. Outside ambient has been quite cold these last few days, but the performance behavior is mimicked whether it is 70f or 15f. Has anyone noticed this? Is this indicative of some looming fault? No codes or shadow codes, either. Car is bone stock except for a VRSF 7" ic. Carbon cleaning was apparently done 5k miles ago by po.
I've checked for boost leaks as well...i replaced all the bad connections with the VRSF kit. No difference.
Thanks,
-Cm

[feuer]

Possible cause would be sticking wastegate. Often happens with out any CEL triggered.

[gurusan]

A bit hard to diagnose without a log of some sort.

[srey]

Run a couple of datalogs. One when the car is running good, and one when it's not. In addition to sticking wastegates I wonder if it could be bad boost solenoids. Regardless, any speculation at this point is worthless without datalogs.

[Cm452]

Forgive the dumb question; is INPA or MHD better for capturing logs? I got inpa to work for dtc and clearing adaptations, but I have yet to develop trust with the software. I got full tools from bimmergeeks if there is a better option like WINKFP, Ncs,etc? I self tuned Saabs for over a decade and the earlier MAP systems were fickle and sensitive to adaptation multipliers, which is why I suspected as such. On those motors the boost control solenoid could also get oil and sludge and schmoo in them, which usually resulted in overboost.
I'm getting MHD anyway fwiw.
Thanks again,
-Cm

[Sgop335]

Originally Posted by Cm452

Forgive the dumb question; is INPA or MHD better for capturing logs? I got inpa to work for dtc and clearing adaptations, but I have yet to develop trust with the software. I got full tools from bimmergeeks if there is a better option like WINKFP, Ncs,etc? I self tuned Saabs for over a decade and the earlier MAP systems were fickle and sensitive to adaptation multipliers, which is why I suspected as such. On those motors the boost control solenoid could also get oil and sludge and schmoo in them, which usually resulted in overboost.
I'm getting MHD anyway fwiw.
Thanks again,
-Cm

Mhd is the way to go for logs. In case you are unaware, you can dl just the monitor module for logs $49. Dont need flash or maps if not ready. Of course code reading is free w mhd.

[catcher22]

Could be anything. I agree with the datalogs.

Before I changed my boost lines, my car would experience similar symptoms (sluggish in the city, fine on the highway). But like I said, it really could be anything.

[Cm452]

I got logs, but they don't show anything that I saw as indicative of any fault. Target boost was 5-6psi and it hit it dead on. Wgdc was like ~30%. I do occasionally get 2cfb throttle codes, but they only pop up after a battery disconnect, AFAIK. Also pedal is 100% but throttle value stays stuck at ~80. Inpa shows the same. Lastly, it pulls like 5-7 degrees of timing in 4th only, but not 1-3, independent of heatsoak.
The cars runs like a scalded cat after it's been warmed up. It is slow and angry both when very hot and cold. Unless I'm over 200f oil temp, she doesn't pull.
-Cm

[dpaul]

Excuse my ignorance - how do you log with INPA?

[Cm452]

I dunno; I logged with MHD.
-Cm