Rough Tiguan: O2 Sensor & Rich Fuel Mix Warning Signs

Had the same symptoms on my 2018 VW Golf GTI. The rough running and power loss turned out to be faulty fuel injectors causing an inconsistent air-fuel ratio. The intake manifold pressure readings were all over the place, indicating poor fuel atomization. The diagnosis showed two injectors were sticking open, flooding the engine with excess fuel. This explained both the rich mixture and terrible fuel economy. The scan tool confirmed multiple misfires due to the bad injectors. This is a serious issue that needs proper attention. Continuing to drive with faulty injectors can damage your catalytic converter from the constant rich mixture. When mine was fixed, they had to replace all fuel injectors as a set to ensure balanced fuel delivery. The symptoms are classic signs of injection problems, rough acceleration, high fuel consumption, and unstable idle. Getting this diagnosed and repaired quickly is important. The repair requires specialized diagnostic equipment and expertise with direct injection systems common in modern VW engines. Looking at your kilometers and model year, this could be a similar injector issue, especially if you notice black smoke or smell raw fuel occasionally.

Thanks for sharing your GTI experience. Your symptoms match exactly what I dealt with in my Tiguan recently. Mine also had rough running and the check engine light, but the mechanic found it was caused by a combination of clogged fuel injectors and a failing spark plug that messed up the air-fuel ratio. How much did your injector replacement end up costing? My repair was just done last month and I am curious to compare prices. Also, have you noticed any other issues popping up since the fix? My engine runs smooth now but I want to stay ahead of potential problems by replacing the air filter next service.

Just got your message about the repair costs. Glad to hear your Tiguan is running smoothly now. The total for my injector replacement came to 515€, which included parts and labor. The shop confirmed the rich mixture issue was completely resolved after the repair. Since fixing the faulty injector, the engine has been performing perfectly. Fuel economy returned to normal and the check engine light hasnt come back. The oxygen sensor readings are now steady, showing proper air-fuel ratio control. Replacing the air filter is smart preventive maintenance. A clean air filter helps maintain optimal fuel mixture and protects those injectors we just had fixed. The catalytic converter will also last longer when the engine runs at the correct mixture. Its been about 8 months since my repair and zero issues since. The rough running, power loss, and high fuel consumption are all gone. Keep an eye on your fuel consumption, if it stays normal, thats a good sign the repair was done right.

Thanks for the helpful advice. I finally got my Tiguan fixed last week. After reading the responses here, I took it to a different shop that specializes in VW fuel systems. Smart move, they found multiple issues causing the rich mixture. The air filter was completely clogged, the oxygen sensor had failed, and two fuel injectors needed cleaning. Total repair came to 680€ but worth every cent. The engine runs perfectly now, no more rough idle or power loss during acceleration. Fuel economy is back to normal too. The mechanic showed me the old parts and explained how they affected engine performance. Really appreciated their thorough diagnostic approach instead of just throwing parts at the problem like my previous shop. Makes sense about protecting the catalytic converter by fixing fuel mixture issues quickly. The intake manifold was also cleaned as part of the service. Going to stick with this new shop for future maintenance, they clearly know their stuff.