Analyze my boost graph

isnt the N18 just an N75 with a black head on it.. can he not swap those out as a test?

not sure on the 99.5s but is for true on the 2000+ ALHs.

If you get good measured vacuum response using the output test on the N75, that points to the N75 being ok. Worth swapping with the N18 though if that works for 99.5s.

Did you try taking off the actuator arm by removing the circlip, and feeling the VNT lever by hand? It is difficult to really assess the mechanism with the spring pressure of the actuator working against it. The VNT ring can wear a small groove into it which can cause intermittent sticking separate from the general crunchiness due to carbon buildup.

I'm still confused about your log from post #15, and why the ECU is requesting full duty cycle (reduce boost) on the N75 when you were underboosting. Did you sort out the potential boost leak from the intercooler?

Yes, works for 99.5. Same set-up, only difference I know of is the wire connect to the N75.

Follow up - Richard at CoolAirVW hooked me up with an N75. That has fixed the code and the car no longer goes into limp mode, but I've still got constant low power. Numbers look similar. MPG have dropped down to about 42-43 MPG, down from about 48-50 last fall. I think I may be about done with this thing...

Group 1 - Field 0 Group 3 - Field 1 Group 3 - Field 2 Group 11 - Field 1 Group 11 - Field 2 Group 11 - Field 3
Engine Speed - (G28) Air Mass - Specified Air Mass - Actual Boost - Specified Boost - Actual Charge Pressure - (N75) Solenoid
/min mg/str mg/str mbar mbar %
1596 670 425 1744.2 1152.6 31.1
1743 800 675 1815.6 1438.2 24.7
1932 795 865 1907.4 1785 45.4
2100 790 1030 1948.2 2060.4 57.8
2268 795 1120 1948.2 2223.6 67.3
2415 800 1180 1948.2 2335.8 80.1
2583 795 1205 1948.2 2407.2 92.8
2730 795 1215 1948.2 2437.8 94.4
2898 800 1155 1948.2 2356.2 93.6
3066 805 1110 1948.2 2335.8 94.4
3234 810 1105 1948.2 2346 94.4
3318 810 1060 1948.2 2091 92.4
3381 815 835 1948.2 1795.2 92.4
3465 815 785 1948.2 1734 92.4
3528 825 780 1948.2 1723.8 92.4
3591 835 780 1948.2 1723.8 92.4
3654 845 775 1948.2 1734 92.4
3696 850 780 1948.2 1734 92.4
3759 850 775 1948.2 1744.2 92.4
3801 850 770 1948.2 1744.2 92.4
3843 850 770 1948.2 1744.2 92.4
3339 850 765 1081.2 1744.2 92.4
2793 515 660 1519.8 1387.2 92.4
2835 685 710 1581 1550.4 92.4
2877 730 690 1703.4 1519.8 92.4
2919 740 760 1693.2 1581 92.4
2814 740 750 1621.8 1591.2 92.4
2289 280 530 1142.4 1183.2 92.4
2310 505 480 1264.8 1193.4 92.4

Maybe your actuator rod needs to be adjusted.

Will just mention MAP. Probably should see what it reads (without starting engine you want to capture the sitting value). I'm not very knowledgeable on issues here; not really grasping how it could be an issue here but I figured I'd toss it out as a muse.

UhOh said:

Maybe your actuator rod needs to be adjusted.

Will just mention MAP. Probably should see what it reads (without starting engine you want to capture the sitting value). I'm not very knowledgeable on issues here; not really grasping how it could be an issue here but I figured I'd toss it out as a muse.

Click to expand...

Thanks, I'll do some research on MAP and see what's going on there. Richard at CoolAirVW suggested rod adjustment if the N75 didn't work. I'm hesitant to do that as this issue wasn't present last fall and seems to have slowly gotten worse since winter. His other thought was it's something turbo related.

Rod adjustment is what I just mentioned in your other thread (prior to reading this- Richard is, I'm guessing, correct).

Can we pick one thread or the other to follow through on this?