Just the other day, I started up my GTI, after it had sit for ~3 days and the Check Engine light was on. It seemed to be idling OK, maybe a little rough, but after 3 days of sitting it did not seem abnormal. I decided not to drive it, and have not tried to start it since. I did a search on previous posts. Some posts I found mentioned loose plug wire or loose distributor cap. It's been about 8 months since I did a cap, rotor and plugs (same wires though), so I'm not in the same situation like other people where either they were in need of changing these, or they recently replaced them and did not get a plug wire on firmly.
So, one of my questions is, does the check engine light come in a regular intervals (like the O2 sensor light does in other VWs based only on mileage)? I did just roll over 80k miles probably the last time I drove the car before the light came on.
My next question would be (if the answer to the last one is NO) what are the systems that can trip the check engine light? I am assuming from previous posts that the OBD system monitors spark in some way. Does it also monitor air flow? (like maybe I need a new air filer or have a dirty MAF sensor?)
Well, I'll stop there and see what kind of feedback I get. Thanks. Charles