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W124 400E, W126 500SE
971 Posts
Discussion Starter #1 (Edited)
I'm still investigating my stalling issue. I've changed the MAF potenciometer (a trusted engineer did this, the basic position was adjusted ad the old one). Now duty cycle reads 10% until the throttle is raised, then it starts reading lambda duty cycle.

We also measured the O2 sensor, and it is reading lean all the time when idling, and only starts oscillating when throttle is raised (and the mixture adjusted rich). We could get it oscillating/reading in idle with really rich mixture, but duty cycle remained at 10% - but I try restarting engine after that. We leaned it down because it was really really running rough how rich it was...

Since those two are connected, is it a O2 sensor fault causing the constant 10% until it catches up? Or did we screw the potenciometer? (I didn't read duty cycle just before the change, but week ago it was reading at idle 45-55% just fine).

The car's behaviour didn't change at all, if anything, I think it's actually worse than before :-(

TL;DR - Does faulty O2 sensor cause duty cycle to stay at 10%?

EDIT: just figured out the service manual, the potentiometer is faulty or wrongly set, I'll adjust it, but I'm not sure that's the problem :/
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