Hello all,

I'm posting another thread to my existing one I had up about a few weeks ago in regards to a classic check engine light.

I have a 2000 Golf GLS 4 door 2.0 non-turbo engine that recently has encountered the classic check engine light.
Overall it really didn't seem anything major wrongmechanically. As a precaution I took it to a mechanic and got an error code saying the timing on the #2 cylinder was misfiring, but wasn't really too bad. I had it reset and it did not come back on for another 600 miles upon my odometer reading.

I noticed the time it came back on after 600 miles was when I started from idle in second gear causing the oxygen sensor to misread the timing? Because, prior to the engine light coming back on I was deliberately careful not to downshift or shift inapporpriately to avoid the light coming back on during the course of those 600 miles.

So, anyway one day the engine or exhauset system seemed it was starving for air or gas like the muffler got clogged with something. I tookit to mymechanic again because I alsohad another noise coming from the bottom of my car that was annoyingthe hell out of meand thought I'd kill 2 birds with one stone. My mechanic told me it was the catalytic converter.

Well, I took his advice and bought an aftermarket one and had it installed. But, the engine seemed ok once again after the clogging incident and prior to the new cat.

Upon installing the new catalytic converter the idling was rough immediately especially on idle. I thought perhaps the 02 sensor needed time to adjust to the computer. The old cat looked like it was burning of sulfur as when looking inside it was apretty blackish white powder and seemed there was nothing inside of it.

I've rode it for 2 days now and seemed better upon shifting from 1st to 2nd gear prior to the new cat and sluggish on 3rd & 4th gear. On the 2nd day the 1st & 2nd gear was sluggish and the 3rd, 4th & 5th gear were fine. It's when the car is at idle sometimes it shakes a little, not at all and sometimes shakes pretty hard.

The question is: Will I need to get another 02 sensor, wait until the rough idling smooths itself out, or could it be the mass air flow sensor? It was replaced less than 6 months ago.

I tried to reset the computer by pulling out the negative battery terminal twice to no avail.

ANY SUGGESTIONS?

If it's a part I need to get and it's not expensive I will try most anything. SO, please anyone with knowledge or experience to my situation I am ALL EARS. Thanks again.