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1995 E320 Wagon, 2002 S430
595 Posts
Discussion Starter #1 (Edited)
Please help -- Extremely high duty cycle, air/fuel mixture crazy lean

correction... high duty cycle = too lean. I had it backwards when I first posted this so I went in a made some changes to reflect this

Trying to figure out why my engine requires 78-81% duty cycle air/fuel mixture on a 91 300E. The minute I try to richen it the engine starts running extremely rough and threatens to die. It needs the 78-81% to idle smoothly. But of course it runs like a dog a lower RPMs with a mixture this lean and gets heinous fuel economy. I have one confirmed vaccum leak on the small hose going from the air intake to a part on the right side of the engine connected to the fuel line junction. Not sure what you would call this part, anyone? Please refer to the pictures below to see which hose I am talking about and which part I am taking about.

Something else has to be wrong however. I will be replacing the oxygen sensor and engine temp sensor tomorrow and replacing that broken hose to mend the vacuum leak, but still, something else has to be causing this. No? Any ideas? EHA maybe? I don't see it leaking fuel around the EHA.

Ignition system has new plugs, wires, cap, rotor.

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