Question about 2003 Volkswagen Passat
The catalytic converter will glow red hot when it is burning unburned fuel from the cylinders. One very probably cause is that one of the cylinders is not firing because it has a bad coil. If that is the case, the engine should be running very rough. To find out which coil... either get the engine code read, or unplug the wire from the coil and see if the engine does not run any rougher (put the plug back on quickly because that is more fuel not being burned. Replace that coil with new one from auto parts store (about $30).
IMPORTANT... do not try to figure out what coil is bad by unplugging the coil itself from the spark plug... if you touch the side of the cylinder head with the bottom of the coil, you will short it out and have to buy another one (I speak from experience).
RECOMMENDED - buy one extra coil and keep it in the car. Whenever your car starts to run very rough and have low power, pull over and replace the bad one. It takes 5 minutes tops, and only needs a dime to get the engine cover off. No other tools necessary (well... something to move the connector lock).
Another reason could be it's running rich. That is possible if the Mass Airflow Sensor is bad, or possibly the cam position sensor. These are easy to replace with a Google search showing how.
If your catalytic converter is glowing red hot, you have probably wrecked it. It _may_ be ok, but likely is fried and your engine light will be on and the code will indicate you have low efficiency on catalytic converter on bank X. If a 4 cylinder, then it will always be bank 1 because there is only one. If a V6, then it will be one of the two banks. But it will be the one that glowed red. Cats are expensive, and expensive to install, so if you see your cat glowing red, do not drive the car. Not to mention, Passats leak so much oil that it is a fire hazard.
Posted on Oct 26, 2013
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Posted on Jan 02, 2017
as per vw, you need to check transmission oil level., not an easy thing to do. if transmission oil level ok (no dipstick on these by the way). it is a mecahnical fault.
Posted on Mar 10, 2009
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