Code P0172 on fuel mixture for 2000 Volkswagen with 1.8 Turbocharged engines

Question:

This code came up on dash P0172 system mixture too rich and as per ATS past newsletters, I changed the mass air flow sensor but the code remains. I tested it for vacuum leak but cannot find any. The engine ran fine but won't pass emission. Any suggestion?

ATS Advisor:

If this is a regular fuel injected engine, I would recommend checking the fuel regulator which could have a ruptured diaphragm. However, since this is turbo charged, it is very common for the vacuum connection going to it to leak. It's made of plastic and called a suction jet pump which is similar to a pcv valve. This part usually fails and will cause a vacuum leak when the engine is boosted by the turbo. The computer will make up for it by injecting more fuel causing the rich condition. Check and repair this leak and this should fix it.

ATS Tips:

Contact ATS if you need the vacuum diagram for these turbo vacuum lines.
The vacuum hoses are expensive and must be handled with extreme care