Hello.

I have a 560SEL that has a slight rough idle in park. It’s goes away in drive. It’s also running very rich, so much that it’s left a black mark on my shop floor and smokes a gas smelling smoke. I think the 2 are related. I have check the 02 sensor, new wires, cap, plugs & button. I have sprayed enough either in the shop to get high looking for a vacuum leak. It has good vacuum on the gauge. I have checked the cold start injector it’s not spraying when it’s warm. I have tried to adjust it in the TB plate via the hex key but still have the stumble. I have taken the lines off the injectors and cleaned them and sprayed cleaner in the pump ports and injector input ports. Have not taken them out to soak. I can listen with a theta scope after I clean them and they have a nice whoosh and click to them but after a while the make a screaming sound as if fuel was getting forced past them. High fuel pressure? Can there be such on a mechanical system? I have read post here till I was blue in the face about rough idle but I would not call this rough it’s more of a bumping or stumbling. It’s not to bad “Yet” but this and bad gas milage is what it came into my shop about. This car is a tad older than I work on and is somewhat of a mystery. If it’s not EFI or OBD2 I become a non-mechanic. “LOL” any way, any ideas, let me know. It’s not lean, and it’s not a miss, it’s more of a sporadic bumbling at idle in park. No idle speed issue, No lean condition.

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Spookeay Bird.
1985 190
1972 280 SE
1987 190