I have a 1994 E320 wagon with check engine light on. Shop reports MB fault codes 35 and 84 and suggests new air flow sensor and/or O2 sensor. Repair would be in excess of $700 but shop could not guarantee that check engine light would go out. Can anyone provide me some info that would raise my confidence that a new air flow sensor and/or O2 sensor is a good plan? Car runs very well, but intermittantly surges (up to 1200 rpm) when at stop light with transmission in drive. Seems to happen more in cold weather. Placing transmission in park reduces fluctuations. Car has 175,000 miles.

Also, is it possible to make modify or buy a code reader for this make and model so I can read my own fault codes?

Thanks.

J. M. van Swaay