Hello everyone! I opened a thread in the past with the unusual behavior of my 1993 320 CE that sometimes stalls when I accelerate to get moving after a traffic light. In the meantime, I thought I found the problem after diagnosing the car with a HFM scanner tool. Although I changed the oxigen sensor with a new Bosch unit, the O2 sensor control goes up to 20-25% while ideling. While I drive is between the usual margins, less than 10%. But as soon as I take the food off the accelerator, is goes up.
Anyway, somebody proposed to change the MAF with a spare one he had (also an OE Bosch unit) and voila, the car even feels different, there are no random shakes while idleing, the O2 sensor control is less than 10%, and while driving it goes around 0% +- some. So I’ve started searching for a good MAF (I had to return the one I’ve borrowed) and after picking 3 units from junkyards and 2 more from eBay all across Europe, none of them seem to be in good working condition (same high O2 sensor control and very subtle random tremur at idle). So I’ve became suspicious (I can’t be that unlucky) and asked another friend to let me test those MAFs on his car. Surprise: they all work fine. All the ones I’ve bought and the one I borrowed. Small differences, but O2 sensor control is between safe margins. Now what?
I’ve looked again over the numbers in HFM scan. One thing that looks odd is that the O2 sense voltage is very fluctuant (most of the time between 700 and 500 mV, but every of few seconds it drops to 70-80 mV, then goes back to hundreds). Looks like a very abrupt sinusoidal curve. Then is the throttle angle while idleing. At my car, is at 0,4 degrees, and HFM scan highlights it in red, so maybe there’s also a problem.
Somebody suggested that it might be the case of a misalignment in the intake timing shift. Or maybe a bad ECU? What should I do next?
PS: the engine loom was rebuilt, the HG replaced last year, the engine seems lively, there are no errors stored or permanent, but I can’t ignore this odd behavior. So please shoot whatever goes through your mind. Thank you!
Anyway, somebody proposed to change the MAF with a spare one he had (also an OE Bosch unit) and voila, the car even feels different, there are no random shakes while idleing, the O2 sensor control is less than 10%, and while driving it goes around 0% +- some. So I’ve started searching for a good MAF (I had to return the one I’ve borrowed) and after picking 3 units from junkyards and 2 more from eBay all across Europe, none of them seem to be in good working condition (same high O2 sensor control and very subtle random tremur at idle). So I’ve became suspicious (I can’t be that unlucky) and asked another friend to let me test those MAFs on his car. Surprise: they all work fine. All the ones I’ve bought and the one I borrowed. Small differences, but O2 sensor control is between safe margins. Now what?
I’ve looked again over the numbers in HFM scan. One thing that looks odd is that the O2 sense voltage is very fluctuant (most of the time between 700 and 500 mV, but every of few seconds it drops to 70-80 mV, then goes back to hundreds). Looks like a very abrupt sinusoidal curve. Then is the throttle angle while idleing. At my car, is at 0,4 degrees, and HFM scan highlights it in red, so maybe there’s also a problem.
Somebody suggested that it might be the case of a misalignment in the intake timing shift. Or maybe a bad ECU? What should I do next?
PS: the engine loom was rebuilt, the HG replaced last year, the engine seems lively, there are no errors stored or permanent, but I can’t ignore this odd behavior. So please shoot whatever goes through your mind. Thank you!
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