My 1995 E320 starts fine when the engine is cold, but when it is hot it fails to start. The engine turns over and I can hear the fuel pump working. If I depress the gas pedal about 2" and turn the engine over it starts ok, when I let off the gas it hesitates and run rough (low rpm) and then smoothes out.
I tested the built in led and got a fault code 25 "knock sensor" only. Could this cause the problem or should I look elsewhere?

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1995 Mercedes E320