Volkswagen: Catalytic Converter, 2001 Jetta & gas mileage, coolant temperature sensor, fuel pressure regulator

Question
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Followup To
Question -
Howdy,

Referring to: 2001 Wolfsburg Edition Jetta manual transmission 105,000+ miles.

Mechanics at my VW dealership determined that my 2001 Jetta needs a new catalytic converter (the check engine light has been on and that was their diagnosis). Since that time, my gas mileage has dropped by 5 mpg. Does this make sense? Is the catalytic converter & gas mileage intertwined? Or do you think something else might be going on with my car?

Thanks!

Answer -
Hey Patrick,

Has the converter been replaced and you lost 5 MPG, or was that only a diagnosis?

Thanks,

Ron

Hi Ron,

Sorry for the confusion. No, the converter was not replaced, I'm still operating with the old one. Thanks!

Patrick

Answer
The Catalytic converter would improve gas mileage if removed, but would fail emissions.  I would suggest asking the dealership to provide you a report of the error codes that printed out while doing the diagnostic tests.

Some things that may cause poor gas milage:

1) Dirty Air Filter
2) Fouled or bad Spark Plugs
3) Faulty O2 sensor
4) Coolant Temperature Sensor faulty
5) Fuel pressure regulator faulty

I would most likely guess that #1 or #2 would be the culprit.  Finally, your existing cat. converter should not be compromising your gas milage unless it is clogged.

Ron