doubt thats it,,,, i run my resisted temp sensor in negitive degree weather. seems faster in the cold to me (air is more dense). I would recommend checking the ignition system or maybe replacing your R-16 resistor if your engine really sounds like a diesel. you definately don't want preignition. what octane fuel are you running?

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Current Stable:
01 ML55 AMG
92 500E (a few mods)
87 300E (lots of mods)
00 Chevy 3500HD Diesel Box Truck
68 18' Donzi Marine
06 GT i-Drive7 1.0 Mountain Bike (with GPS!)

PREVIOUSLY OWNED:83 300SD, 87 420SEL, 88 420SEL, 90 420SEL, 86 560SEL, 86 190E 2.3-16V AMG, 94 E320