1989 XJ40 overheating problem

Could be worthwhile always the chance of an item being bad out of the box.

Robin …

I’ve certainly had to deal with 1 or 2 malfunctioning items out of the box in the past, not very common but not unheard of. I’ll try to get a readout on the O2 sensor tomorrow.

Found this in my notes this morning - some figures on the coolant sensor …

Ice water 32 deg F = 5900 ohms

Boiling water 212 deg F = 0190 ohms

Pull the sensor and calibrate against the numbers . Also a bad connector goes high resistance mimicking cold coolant thereby enriching fuel mixture.

Dennis, a new O2 sensor without the heat shield triggered a CEL and a FF44 when I did it few years ago. Did your old sensor have a heat shield?

Joe …

No O2 sensor heat shield on my '89 as far as I can determine.