Misdiagnosis MAF, MAP ...Turbo Replacement ...Old MAF Reinstall: finally fixed!(part

10packsAday

Member
Joined
Jan 20, 2017
Location
Unite States
TDI
2003 mk4 Jetta 1.9 TDI ALH
Misdiagnosed MAF, MAP ...Turbo Replacement ...Old MAF Reinstall: fixed!(part number)

Hello, just a friendly reminder to always check part-numbers carefully before purchasing new sensors. Take the MAF sensor on my mk4 1.9tdi for example: the housing may look the same, although the sensor insert is not necessarily the same, if you look closely inside the housing you may see a small capacitor hidden inside the air scoop; or you may see a flat plate-like-thing as in my 1.9L diesel MAF. If you check on parts.vw.com you will also find they have different part numbers:

1.8L MAF Part Number: 06A906461LX
2.0L MAF Part Number: 06A906461G
2.8L MAF Part Number: 071906461BX
1.9L DIESEL MAF Part Number: 038906461C

Anyway, my whole story started around 200k miles when I started having some hesitations/low-power problems. Eventually the problem got so bad that the engine started kicking into "limp-mode". I had already begun to try and diagnose the problem before I had the overboost and limp-mode problem, although the naive, and 5 years younger, version of myself wasn't able to figure it out, and I initially suspected my MAF sensor. This was obviously not the problem, but kicked off my ~5 year & ~30k mile quest in car fixing which has lead me to the present day. It's been quite a learning experience, and in the meantime I've replaced both front CV, both tie-rods, rebuilt 4 brake calipers, and done a whole bunch of interior/cabin stuff aside from all the poking around related to my power issue. As for the power issue, for starters I had all sorts of mouse damage to my vacuum lines, and then oil-stains around my EGR which lead me to believe mistakenly my EGR was the culprit, I also cleaned out my intercooler and replaced the MAP sensor(maybe shouldn't have done that last one). When that didn't work, I finally disassembled the whole back of the engine(intake, exhaust, egr-cooler), and replaced my turbo. Turns out, there was some obvious play in the actuator for the turbo, and immediately after swapping in a new turbo my problem with limp-mode resolved itself; although oddly I was still having hesitation/unsteady-throttle, plus smoky cold-starts/rough-starts/hard-starts. Finally I had the good idea the other day to try putting my old MAF back in. Luckily I had kept the old MAF, so I put it back in and now it starts cleanly and doesn't smoke... MAGIC! ...there is still some minor pulsing/dancing in power output, although nowhere near as much as there was, and much more power! ...perhaps I might try putting back in my old MAP(if i can find where I put it).

Long story short, always double check part numbers. It's been a hell of a time fixing this car(being a total amateur) without swapping out perfectly good components for parts meant for a different model.

...Anyway, don't vape & stay in school ;P ...eat your vegetables every day, and get some plenty of sunshine. ...and don't go near anyone, don't hug or kiss. ...and wash your hands!
 

wonneber

Top Post Dawg
Joined
Oct 12, 2011
Location
Monroe, NY, USA
TDI
2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
Glad you got it figured out.

One point I see posted often is our cars do not always respond to non Bosch electronics.
They can even throw in other problems.
In the early days I found this out quickly.
 

10packsAday

Member
Joined
Jan 20, 2017
Location
Unite States
TDI
2003 mk4 Jetta 1.9 TDI ALH
Well not quite done yet. I'm still thinking I should check my MAP, I can't remember if i actually changed it or not. turns out there are 2 different sensors(they transitioned from one to the other around 2003):

https://parts.vw.com/p/Volkswagen_2...charger-Boost-Sensor/51807041/03G906051D.html
Part Number: 03G906051D
Supersession(s): 038906051B; 03G-906-051-D; 3G906051D

https://parts.vw.com/p/Volkswagen_2...ocharger-Boost-Sensor/47992790/038906051.html
Part Number: 038906051
Supersession(s): 038-906-051; 38906051

Now that I think it over, I'm pretty sure I did not replace my MAP, but rather left it in place when I realized the original and my replacement were not the same part. Still, there is something causing my throttle to move on it's own a bit. Also after flooring it a bit the other day, now I am receiving slightly less power at lower rpm range. I wonder if I have a leak in my intercooler?

anyway...and wash your hands. ...don't hug or kiss!
 
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