Hi guys!

I own this -01 Golf Mk4 (Estate/Variant version, not that it matters, but anyways.. ^^) that runs good BUT has some issues. Occasionally, and often after me having put on some acceleration, the CEL lights itself and a diagnosis shows Oxygen sensor no signal (intermittent). A bit weird, intermittent gives the impression that it could be a loose connection, but given the fact that it pretty much always actuates under acceleration gives me reason to believe otherwise. Also, the temperature gauge is weird. It never goes to the middle point, after driving a while it gets perhaps 1/4 or the way, meaning on the very VERY low side of working temperature. The heater gives good warmth inside the cabin however, removing moisture from the windshield effectively etc., so it's not completely cold. Is this AZD engine by design or is something wrong? Also, occasionally the CEL has lit up with fault code about temperature sensor "signal too high". Does this mean that MAYBE the thermostat is actually opening correctly and all, but the sensor is worn and giving me lower-than-actual readings constantly? And third, occasionally the oil light is turned on. Not the red one (pressure) but the yellow (low oil). I check the oil and it's stable as ever, in between the marks. Most probably the oil sensor underneath the oil tray, right? Ideas on which order to resolve these issues? The car is drivable but I would like to fix it to become perfect, happily not having to "throw parts at it" i.e. replacing parts that won't need replacement. So, any experienced mechanic who could aim me in the right direction of trouble-shooting these issues? Cheers!