Hi guys.

My m119 is sluggish and cold start is weird. Sometimes engine runs OK but most of the time it is sluggish. When you accelerate it picks up speed then it bugs down for a second or two around 1700rmps then it picks up speed again. Cold start will keep rpms up to 1000 for about 1-2 munites then drops it to 650. And it will not keep transmission in 2nd gear for longer time. It shifts as the engine fully warm. I have coolant temperature sensor that is black and has 4 terminals replaced but nothing changed. Also when you drive a car cold it backfires into intake if you give too much gas. Rarely but it happens. Any ideas what can it be?

Thanks.

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1999 ML430 Silver 135k ml
Smoked LED taillights, Alpine in-dash DVD player, 12" sub, Pioneer components, 2 amps, 4200k HIDs, ML55 headlights, 20" rims, mirror LED blinkers

SOLD. 1996 E320 145k ml. Burgundy

SOLD but miss it everyday 1992 500sel Black
Chime buzzer mod,Alpine CD/MP3 player with stock amp,Euro headlights,S600 grill,20" rims, BEST CAR EVER!

SOLD. 1990 300E White
187k ml,smoked tails,Euro headlights,17rims,Intake,12" sub in first aid kit,alarm/autostart,buzzer mod