Quote:
Originally Posted by Stl-986
It will run richer. If it runs really rich you could even smell it. Have an 01 S I am working on right now that has a leak and is running rich enough you can smell it in the air.
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Help me understand how. My understanding is that the MAF meters the air coming in and the ECU adjusts fuel accordingly. If you have a vacuum leak, there is unmetered air coming in, causing a higher air to fuel mixture, thus lean. The air/fuel (O2) sensor would sense a lean mixture and tell the ECU. The ECU would enrich the fuel trim to compensate. If the Fuel Trim reaches its limits and still can't get it rich enough, the ECU throw a P0171. System too lean.
What am I getting wrong here? How would a vacuum leak cause a rich mixture?
Thanks.