I used to have the same problem...

It turned out to be the temp sender (the blue sensor) which is located below the cover right in front of the airbox.

I figured it was impossible for the engine to be operating at 60 the whole day in 40C degree weather...

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Rainmaker
93 500E, 43k mi, Pics of upgrade parts
Evo II Wheels on Dunlop FM901 235/45x17s
94 Facelift
RennTech CF Airbox
RennTech ASR Defeat
RennTech Chip
1st Gear Start
97 Range Rover 4.6 HSE Vitesse, Yellow, "Tonka" (sold)