Questions and Answers

Volkswagen Jetta Code P0172 Q. Vincent, Great site! I've been having problems with my 2000 Volkswagen Jetta. Manual transmission with the 2.0 liter. It's got 36,000 miles on it. My check engine light came on during highway driving. I pulled off and let it idle to see how the engine sounded. It sounded a little rough, but the tachometer stays around 700-750 rpm and I've had no drivability problems.

I checked the oil, and found that it was about 1½ quarts low, and there was foam around the inside of the oil cap. The OBD-II code is P0172, which indicates a rich fuel/air mixture on Bank 1. I am not sure if the two problems are related, but am giving you as much info as I have in order to possibly diagnose my problem. Any ideas?

Thanks!
Grant

A. Code P0172 is most often caused by a bad fuel pressure regulator or a bad fuel injector. You will need to do a fuel pressure test to determine which is exactly the problem.

The white foam inside the oil cap is nothing serious. It is just condensation and comes and goes with the seasons. You can check the PCV Valve and PCV heater for proper operation, other than that there is not much you can do.