I don't know what they tested, IF anything. When they said they couldn't determine what it was, but would gladly start replacing expensive parts to see if it would help, I figured it was best to just pick it up from them.

When cold it seems to idle much rougher and have major hesitation. Once warm the idle is less rough usually, but seems to be rough when I come to a stop from 45-50 mph or getting off the freeway etc.

When I take off from a stop sometimes it hesitates like it is going to die and other times its moderate in nature. When I try to downshift to 1st gear, it really struggles and misfires even more until I let off the accelerator a bit.

Last night I drove it while raining and it seemed to idle and perform very well.

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Mercedes Fleet:
2004 CL600 Designo Espresso SPORT
2004 S600 Designo Espresso SPORT/Lorinser Pkg.
1999 S320
1988 300TE
1972 280SEL 4.5
Diesel Fleet:
2014 GL350 Blutec
1987 300SDL Blk/Blk 4 place seating #18 head
1987 300SDL Smk Slv/Burgangy #17 head
1986 300SDL Blk Pearl/Palomino #14 head w/ 280K
1984 Lincoln Mark VII Fact BMW Turbo Diesel