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gomi_otaku, VW Technician
Category: VW
Satisfied Customers: 3457
Experience:  VW FastTrack '00-'01, VW Academy Chicago and Seattle '00-present, VW Certified
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I have a VW Passat 1,4 ecofuel, engine cdga 110kW MY 2010

Customer Question

Hi, I have a VW Passat 1,4 ecofuel, engine cdga 110kW MY 2010
DTC P2177
I have checked intake system for leaks but could not detect any. Sprayed all hoses and gaskets with start gas but no reaction.
Got any ideas where to begin?
Kind Regards
Submitted: 1 year ago.
Category: VW
Expert:  gomi_otaku replied 1 year ago.

These are pretty sensitive to any air leaks. Make sure that your oil cap and dipstick are both seated fully. With the engine running, try taking the oil cap off- see if it sucks down really hard and is difficult to remove.

Otherwise, I would suspect the Mass Air Flow sensor...

Customer: replied 1 year ago.
Ok, sounds ok. I forgot to mention that after erasing the DTC it took about one week and 1000 miles before the MIL iluminated again. Can that give an extra clue?
Expert:  gomi_otaku replied 1 year ago.

What are you using to scan the fault codes?

Customer: replied 1 year ago.
A SUN pdl 1000 but it´s to old for coming in to the VW menu so I just read the OBD
Expert:  gomi_otaku replied 1 year ago.

You may want to try spraying the MAF out with some electrical cleaner (something that will not leave any residue) and see if it returns.

Customer: replied 1 year ago.
I tried to do some thinking. :-)
The milage of the car is 180000 km (110 000 miles)
Can it be the diagnostic O2-sensor. But if so, it would give increased HC in the exhaust due to the sensors intention to compensate for falsely measured lean running. Unfortunately I don´t have an instrument for measuring the exhaust gas.
I read that it might be the fuel pump not delivering enough pressure. What is the correct pressure and at what conditions, idle?
Is it clear that this DTC dependon the "gasoline" part of the engine or can it be caused by the "methane" part as well?
Can there be any problematic interaction/leak between the to fuels? If e.g. the methane leaks in to the system while driving on gasoline?
Customer: replied 1 year ago.
I'll work with the car in the weekend and start with the MAF. Thank you for your efforts so far.
Please try to respond to my last questions.
I'll give you feedback after the weekend.
Thank you an good night. (it´s that time here in Sweden)
Expert:  gomi_otaku replied 1 year ago.

These systems are pretty smart- if there is an O2 sensor not reading correctly, it will detect it. I think that even if there was bleedthrough from the two systems, the engine management is designed to take that into account (as it has to work at the time that fuels are switched, which would result in some blending)

An O2 sensor ONLY detects oxygen- not any other gas- so if it is saying you are running lean, then it is reading too much oxygen- which can also happen if you are getting an incomplete burn in the chamber, like from worn spark plugs. It can even happen because of a leak in the EXHAUST system, in front of the O2 sensor.

Customer: replied 1 year ago.
Hi, I had the car in today and tried to find the MAF sensor. A little bit disappointing when I after googeling found out that this engine 1,4 TSI does not have any. It has dual MAP sensors. I guess it make no sense to wash off any oil and dust from a piezo sensor.
There was a acceptable "suck" when lifting the oil cap. So no leaks from the crank vent.
I sprayed the whole system with starting gas but no reaction what so ever. No leak.
Got any ideas ( better than the MAF? =D )
Expert:  gomi_otaku replied 1 year ago.

If the oil cap area is sucking too hard, that would indicate that the crankcase vent it open to the intake. It pulls lightly at idle, maybe hold a sheet of paper in place but not enough to hold the cap down.

I've seen a lot of issues with the PCV systems causing these kind of problems, or running rough at idle.

Customer: replied 1 year ago.
It's not sucking to hard. It is just as expected.

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