Matt-98AHU
Loose Nut Behind the Wheel Vendor
I encountered a low power issue rather suddenly on an 05 Passat wagon that's in the family while it was in my possession yesterday for other work.
It included a little bit of a judder, similar feeling to a misfire under load.
As I was poking around some measured value data (including comparing Ross-Tech definitions vs. what I got from VW via ERWIN) I come across block 23.
VW calls it "unit injector solenoid valve operating times".
Under light loads, the numbers vary, average around 40. Under load, the numbers quickly switch negative. Usually further negative than -100.
Decided to compare those numbers with my good-running BRM (PD is a PD is a PD...). Numbers stayed very consistent mostly between 40-50 even upto WOT.
I replaced the fuel filter, power returned and the numbers now consistently stay in the 40-50 range just like the BRM.
So, what do the numbers mean?
This might be a clue:
Taken from the VW Self Study program which was still available for me to download when I was working at a VW dealer. Found in their Online Training.
So, I suspect that the numbers might be a variation of ECM expectations. When the numbers go negative, the solenoids might actually be reaching the closed status faster than usual because they're fighting less pressure internally due to fuel restriction or even air in the system.
So, while PDs don't have needle lift sensors to know precisely when injectors are popping open, it does still have a decent idea based on knowing exactly when the solenoids on the injectors close fully... that is until you get oddly low fuel pressure from something like a lift pump or weak tandem pump... or your bad mechanic deciding to let your 20k fuel filter interval stretch closer to 60k like I did. In which case, since the injectors still pop mechanically based on fuel pressure, as the plunger is slowly depressed and the solenoid closes, it might take fractionally longer to build adequate pressure to pop the injectors than it would under normal circumstances, in which case actual SOI may lag when the computer actually thinks it's happening, unless it can compensate some for seeing the much lower time to get the valve fully closed.
Anyway, just thought it was an interesting bit of tech knowledge on PDs to share.
FWIW, there are a couple threads elsewhere on the interwebz that mention MVB 23, but still not very complete information out there. Hopefully this adds a little clarity, even though I'm not completely sure that my interpretation of the reading variations are correct.
It included a little bit of a judder, similar feeling to a misfire under load.
As I was poking around some measured value data (including comparing Ross-Tech definitions vs. what I got from VW via ERWIN) I come across block 23.
VW calls it "unit injector solenoid valve operating times".
Under light loads, the numbers vary, average around 40. Under load, the numbers quickly switch negative. Usually further negative than -100.
Decided to compare those numbers with my good-running BRM (PD is a PD is a PD...). Numbers stayed very consistent mostly between 40-50 even upto WOT.
I replaced the fuel filter, power returned and the numbers now consistently stay in the 40-50 range just like the BRM.
So, what do the numbers mean?
This might be a clue:
Taken from the VW Self Study program which was still available for me to download when I was working at a VW dealer. Found in their Online Training.
So, I suspect that the numbers might be a variation of ECM expectations. When the numbers go negative, the solenoids might actually be reaching the closed status faster than usual because they're fighting less pressure internally due to fuel restriction or even air in the system.
So, while PDs don't have needle lift sensors to know precisely when injectors are popping open, it does still have a decent idea based on knowing exactly when the solenoids on the injectors close fully... that is until you get oddly low fuel pressure from something like a lift pump or weak tandem pump... or your bad mechanic deciding to let your 20k fuel filter interval stretch closer to 60k like I did. In which case, since the injectors still pop mechanically based on fuel pressure, as the plunger is slowly depressed and the solenoid closes, it might take fractionally longer to build adequate pressure to pop the injectors than it would under normal circumstances, in which case actual SOI may lag when the computer actually thinks it's happening, unless it can compensate some for seeing the much lower time to get the valve fully closed.
Anyway, just thought it was an interesting bit of tech knowledge on PDs to share.
FWIW, there are a couple threads elsewhere on the interwebz that mention MVB 23, but still not very complete information out there. Hopefully this adds a little clarity, even though I'm not completely sure that my interpretation of the reading variations are correct.
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