What difference does coolant temperature make?

What difference does coolant temperature make?

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Pentoman

Original Poster:

4,814 posts

264 months

Tuesday 11th November 2008
quotequote all
How does the engine use the information from the coolant temperature sensor to change things?

I ask because, messing about on my old Jetronic equipped Merc, I've put a resistor in place of the coolant temp sensor to make the computer think it's about 65 degrees celsius. Not that different from the ~80-85 it runs at in normal driving so you wouldn't imagine it would make a difference.

However in truth this wildly changes the driving characteristics of the engine. It particularly improves low-down torque and makes it behave rather jerkily as you come on/off the throttle.


How can such a seemingly small change make such a difference? Does the disparity between an 85 degree engine and a 65 degree temperature reading make it wildly out?? Even when the engine is 65 degrees it doesn't seem to drive as normal so I've probably put the resistor in wrong!