I posted a longish message about my gas mileage being reduced after
doing extensive/expensive work on my V12. I mentioned that I suspected
and tested the air temp sensor and the coolant temp sensor. I requested
the ohm/degree table for the coolant sensor.
Confirmed ECU water temp sensor not open or shorted
(I need a table of proper ohm values for this sensor)
I don’t know if the sensors used on the Marelli are the same
as on the late model Lucas Digital P, but if they are, this
is supposed to be about the same as the air temp.
He is correct.
The reason I thought they were different is that during my stove top
test last week I was getting resistances in the multi-K ohm range. That
resistance range, per the ROM, translates to 100 degrees below zero. I
retested this same sensor last Saturday, but this time the results were
totally random throughout the temp range. The sensor was bad, but had
not failed to the point that the engine could not run. I reinstalled
the sensor (have to mail order the replacement) so I could drive the
car. Sunday while doing some wiring work I had to remove that sensor’s
plug; when I did so the top of the sensor separated from the body and
came out with the plug. Much of the broken surface was dirty,
indicating that it had been partially cracked for a long time. I
installed a resistor in the plug to tell the computer that the engine is
at 185 degrees F. This morning as I drove to work my gas mileage was
above 16 mpg for the first time since I got the car.
I thank each of you who offered suggestions and ideas as I worked on
1991 XJ-S V12 Conv. (with improved gas mileage!)
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