200rpm intermittent increases - A150 Autotronic
11-12-2011, 03:40 AM
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A150
200rpm intermittent increases - A150 Autotronic
Got a weird problem started a couple of thousand miles ago on my 2006 A150 with Autotronic gearbox (at 86000, it's now about 88000).
I had the car in to get transmission oil change and brake fluid change at the main MB dealer here. Literally a couple of days later, I noticed a slight juddering when in slow moving traffic, nothing concrete but just a feeling that the car wasn't running as smoothly. Further, I noticed it happening more often, and did some tests.
It seems the slight juddering I feel through the wheel coincides with the engine revs suddenly increasing by 200rpm for a couple of seconds, then suddenly dropping to the original amount. This can be on a perfect flat surface where I'm deliberately holding the revs constant, i.e. it's not the usual rev increase/decrease you'll see on the autotronic 'box. It seems to not do it at all until the engine temp is fully warmed up. Then this little revs 'blip' starts occuring, but it's approximately every 20seconds. If I've been driving for a while (e.g. 45 mins) the frequency increases to about every 10 seconds.
Weirdly, it doesn't do it at idle, or if sitting in neutral (e.g. rev to 2000rpm in 'N' and hold revs there), for example, however I notice it happening in the 1600-3500rpm range, certainly at the 1800-2000rpm that would be normal revs at a constant 40mph.
The symptom occurs whether in C or S auto setting, or in manual mode.
I had the car into the dealer to get it checked but they could not find any fault (obviously, there are no warning lights on the dash), although speculated 'could be gearbox related'. I just find it odd that it's occuring a couple of days after getting the gearbox oil changed - never had the issue before.
As if to justify their labour time, I had a new firmware update for the transmission applied, with the classic 'tested and all ok now' on the worksheet. Of course, working in IT for 20 years, I *know* that firmware updates are done to fixed SPECIFIC issues, and random 'I'll just update the firmware anyway' fixes rarely actually fix anything Needless to say, the problem still occurs afterwards.
The car is at 88,000 now and I am due to sell it anyway, just very concerned about possibilty of 'new gearbox' and obvious impact on future sale price (it's only worth around £3500 on a trade-in anyway).
Anyone have any ideas? It's almost like a sensor somewhere is playing up... I presume autotronic SHOULD have a working lifespan of much more than 86000? I should note that it hasn't got any worse in 2000 miles.
I had the car in to get transmission oil change and brake fluid change at the main MB dealer here. Literally a couple of days later, I noticed a slight juddering when in slow moving traffic, nothing concrete but just a feeling that the car wasn't running as smoothly. Further, I noticed it happening more often, and did some tests.
It seems the slight juddering I feel through the wheel coincides with the engine revs suddenly increasing by 200rpm for a couple of seconds, then suddenly dropping to the original amount. This can be on a perfect flat surface where I'm deliberately holding the revs constant, i.e. it's not the usual rev increase/decrease you'll see on the autotronic 'box. It seems to not do it at all until the engine temp is fully warmed up. Then this little revs 'blip' starts occuring, but it's approximately every 20seconds. If I've been driving for a while (e.g. 45 mins) the frequency increases to about every 10 seconds.
Weirdly, it doesn't do it at idle, or if sitting in neutral (e.g. rev to 2000rpm in 'N' and hold revs there), for example, however I notice it happening in the 1600-3500rpm range, certainly at the 1800-2000rpm that would be normal revs at a constant 40mph.
The symptom occurs whether in C or S auto setting, or in manual mode.
I had the car into the dealer to get it checked but they could not find any fault (obviously, there are no warning lights on the dash), although speculated 'could be gearbox related'. I just find it odd that it's occuring a couple of days after getting the gearbox oil changed - never had the issue before.
As if to justify their labour time, I had a new firmware update for the transmission applied, with the classic 'tested and all ok now' on the worksheet. Of course, working in IT for 20 years, I *know* that firmware updates are done to fixed SPECIFIC issues, and random 'I'll just update the firmware anyway' fixes rarely actually fix anything Needless to say, the problem still occurs afterwards.
The car is at 88,000 now and I am due to sell it anyway, just very concerned about possibilty of 'new gearbox' and obvious impact on future sale price (it's only worth around £3500 on a trade-in anyway).
Anyone have any ideas? It's almost like a sensor somewhere is playing up... I presume autotronic SHOULD have a working lifespan of much more than 86000? I should note that it hasn't got any worse in 2000 miles.
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