2003 ALH auto trans with P0234 / 16618 code throwing only on uphills under high acceleration/load/passing. Only 82k on the car, I've had it a few thousand miles.
I've gone through the normal Limp diagnosis procedures:
--PO replaced all vacuum lines, all look great and are tight as confirmed with MightyVac at various points in the system.
--Took a MightyVac to the system and found the vacuum pump nipple was loose resulting in low vacuum to the entire system (10-15psi). I swedged the nipple and now have constant 22 inHg vacuum in system. This made a huge difference in driving the car but it still throws the code under same conditions.
--N75 appears to be working fine per basic settings test and MightyVac confirmation.
--Actuator moves fine visually during N75 basic setting test and holds vacuum without leaking. I haven't put it on the lift yet and checked exact pressure levels/adjustment, I am going to do that next.
Here are my VCDS graphs from when it throws the code (going uphill aggressively) and also doing a 0-80ish stent on a slight downhill grade. Pressure is left axis and RPM is right axis. I was hoping someone might be able to read some nuance in here to point me in the right direction for diagnosis.
This first graph shows the moment it throws the code. I'm coming around a corner (zero throttle) then I gun it and it throws the code. The prior section up the mountain looks the same except here the actual boost doesn't drop down as fast and I guess that's why it throws the code:
Here's flooring it on a slightly downhill grade going through the gears:
Images and Excel files of the logs can be found here:
http://ift.tt/2wbF3ql
From what I can tell my MAF might be bad and/or I have some sort of an intake issue because my MAF requested vs. actual is way off. Ambient pressure here is measuring 766 mbar (I'm at 7500' elevation).
My vacuum pump is only putting out 22 inHg which seems to be a bit on the low side but should be OK. Would that cause limp mode under high loads?
I could see how the vanes would get clogged under a long-term low-vacuum condition which limited overall turbo output. Obviously I'd prefer to eliminate other causes first, so I was hoping that someone could provide additional insights as to where I should look for troubleshooting based upon the graphs?
Thanks a lot in advance,
~Josh
I've gone through the normal Limp diagnosis procedures:
--PO replaced all vacuum lines, all look great and are tight as confirmed with MightyVac at various points in the system.
--Took a MightyVac to the system and found the vacuum pump nipple was loose resulting in low vacuum to the entire system (10-15psi). I swedged the nipple and now have constant 22 inHg vacuum in system. This made a huge difference in driving the car but it still throws the code under same conditions.
--N75 appears to be working fine per basic settings test and MightyVac confirmation.
--Actuator moves fine visually during N75 basic setting test and holds vacuum without leaking. I haven't put it on the lift yet and checked exact pressure levels/adjustment, I am going to do that next.
Here are my VCDS graphs from when it throws the code (going uphill aggressively) and also doing a 0-80ish stent on a slight downhill grade. Pressure is left axis and RPM is right axis. I was hoping someone might be able to read some nuance in here to point me in the right direction for diagnosis.
This first graph shows the moment it throws the code. I'm coming around a corner (zero throttle) then I gun it and it throws the code. The prior section up the mountain looks the same except here the actual boost doesn't drop down as fast and I guess that's why it throws the code:
Here's flooring it on a slightly downhill grade going through the gears:
Images and Excel files of the logs can be found here:
http://ift.tt/2wbF3ql
From what I can tell my MAF might be bad and/or I have some sort of an intake issue because my MAF requested vs. actual is way off. Ambient pressure here is measuring 766 mbar (I'm at 7500' elevation).
My vacuum pump is only putting out 22 inHg which seems to be a bit on the low side but should be OK. Would that cause limp mode under high loads?
I could see how the vanes would get clogged under a long-term low-vacuum condition which limited overall turbo output. Obviously I'd prefer to eliminate other causes first, so I was hoping that someone could provide additional insights as to where I should look for troubleshooting based upon the graphs?
Thanks a lot in advance,
~Josh
Overboost - Need Help Reading VCDS Graphs
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