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Discussion Starter · #1 ·
Like the title says I have a rough stumble when slowing down. It isn't all of the time and happens more often in stop and go traffic, when the engine revs up a tiny bit to move ahead and then revs back down when stopping. The lights also dim when this happens, but only slightly. It does not do this when idling, only when slowing to idle. The PCV system is in functioning order (good suction with glove test) and I'm pretty sure it was replaced by the previous owner shortly before I bought it either way. It has never stalled on me, and is just more of an annoyance, but I'm just wondering the possible cause.
 

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Sounds like the ETM. On these drive-by-wire cars there is no idle control valve as the ecm adjusts the throttle angle to control the idle.

The fact that its hunting for idle when in stop and go tells me the contacts are a bit worn. Over time they'll wear to the point where it will not be driveable and you'll begin seeing CEL for throttle pedal sensor or throttle module itself.

Check the label on the front of the ETM, white label is original volvo, yellow label is the update that was likely done under warranty. Either way they go bad eventually. You can try cleaning it out and it may become more stable for a while. Some have been able to use used ETM's off other turbo models, some purchase the xemodex rebuilt units, and a few out there have soldered in new contactless sensors for cheap.

I personally have the xemodex etm and haven't had a single issue for the last 80K miles.
 

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Discussion Starter · #3 ·
Sounds like the ETM. On these drive-by-wire cars there is no idle control valve as the ecm adjusts the throttle angle to control the idle.

The fact that its hunting for idle when in stop and go tells me the contacts are a bit worn. Over time they'll wear to the point where it will not be driveable and you'll begin seeing CEL for throttle pedal sensor or throttle module itself.

Check the label on the front of the ETM, white label is original volvo, yellow label is the update that was likely done under warranty. Either way they go bad eventually. You can try cleaning it out and it may become more stable for a while. Some have been able to use used ETM's off other turbo models, some purchase the xemodex rebuilt units, and a few out there have soldered in new contactless sensors for cheap.

I personally have the xemodex etm and haven't had a single issue for the last 80K miles.
Thank you. I had a hunch it was this, as other things that could be linked to it are either in good health or already replaced and the throttle body is the only thing I haven't checked. I might give it a good cleaning first to see if that helps. Like I said, it's not super bad right now so I suppose I have time.

Something interesting to note is that whenever I reset the ECU adaptions (for tuning purposes) it doesn't do it while relearning, which I find kind of funny. False hope I suppose.
 

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When and if you do clean it, do not use anything to harsh. I would stay away from brake clean. Use an electrical contact cleaner and a clean cloth to wipe it out thoroughly. On my old 99R it happened more when it was hot outside. The etm was replaced under warranty a few months before i took ownership and then i gave it a beating for about 80K miles before it finally **** the bed and burnt valve, bent rod, trans fail, all the above.
 
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