2001 GTI VR6 - O2 Sensor or Mass Air Flow Sensor

[lnghornlee]

I have a 2001 GTI VR6 with 78,000 miles. I was driving along when suddenly the check engine light came on and the car started to run rough. I pulled off the highway at the nearest gas station to see what was going on, when I noticed a strong burning sulphur smell. Is this an oxygen sensor gone bad, or the mass air flow sensor (are they the same?)? Also, how easy is it to replace?

[=loki=]

I know a little about this, but not everything. Here are my thoughts:

The mass airflow sensor (MAF) is not the same as oxygen(O2) sensors, my '97 VR6 has two O2 sensors, one before the catalytic convertor (cat.) and one after and . There reason why there is two is so that (1) the car can tell how efficiently it is burning fuel and (2) the car can tell if the cat. is working (respectively)

The MAF tells your cars engine software how much air is going into the engine, thereby determining how much fuel to add.

Even if the MAF and O2 sensors are pretty crappy, the car will probably still run, but not to it's best. A wrecked MAF will probably screw things up. You can take it off the intake and visually inspect it, or take it somewhere and get it checked out. Fouled O2 sensors may reduce preformance but the car will run fairly well. (I ran for a long time with barley working O2 sensors)

Considering the smell, it could be belt(s), which are really easy to check.
I've also heard that those year VR6's have even crappier coil packs than my '97 does. I think VW even offers free replacements for some later years. A coil pack will cause misfiring and could wreck a cylinder. to check this, find your coil pack (where the ignition wires start -probably on the side of the engine) and spray it with water while the car is running. If the engine starts screwing up, then bad coil pack. Do not push the car (give it more gas) while it is running rough.

Good luck!

[yogegoy]

Could be a bad 02 sensor since it couldn't detect the hard boiled egg smell. If you have idiot lights across your dash, then you'd be going max of 45mph regardless.