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M3 E46 poor acceleration

12K views 19 replies 9 participants last post by  kaym3 
#1 ·
Hi everybody I have a 2002 m3 which is giving me a bit of trouble when trying to accelerate quickly. When I want to accelerate hard it will rev out in what ever gear I am in but when it changes in to the next gear it dies and hovers around 4 or 5000 rpm until you take your foot off the throttle and then it will drive as normal. The car drives as normal with any other throttle setting and only happens when you throttle down hard. It does it in any gear changing mode, all gears work and it has recently had a new smg box fitted to try to solve the problem. The original problem arose by shifting through three or four gears before it died then slowly got worse. The car use to be okay. Any surgestions will be appreciated as bmw have been dissapointing to say the least
 
#2 ·
Seafoam that biatch!!!
 
#8 ·
There are no codes at the moment as they were erased by bmw but my cousin had a code reader on it last time it played up before taking it in to bmw and there were two codes on it one was none selection of gear or something very similar to that wording which was obvious but the other one said hydraulic duty cycle incomplete?
 
#9 ·
Low battery and or compression springs. Two cheap items that are very likely to cause similar issues. Also if you've been doing high rpm racing type shifting you may have cooked a synchro in the tranny. That would also cause a non-selection until the RPMS matched. Other items that can cause this would be a sticky pilot bearing or debris inside the clutch.
I can go into detail if you'd like. PM me.
 
#14 ·
Thanks guys but I already have a new salmon relay and battery on, unfortunately to no avail. Generally the car will select the next gear but fail to rev above 4 or 5000 but occasionally it will miss a gear but will still not rev out unless i take my foot off the accelerator and then drive normaly. Are these compression springs hard to change? I have also read on the forum that the gear selection sensor can be a problem? Any advice on where to start first and any video or pictures on how to do it would be great,cheers guys.
 
#15 ·
I'm near certain it's the compression springs. The GPS will show a pattern in the way that it skips gears, like go from 2-5 or something like that.

Turn the setting on your shift down to 2, drive normally, shift at low RPM. I bet it shifts just fine. As soon as you put your foot into it, or turn up the setting and shift at higher RPM, it will just flash the next gear until you let off. Once you let off and it selects, then you're fine until you shift again.

If that's what it's doing, it's your compression spring. It's not easy to change, but it's definitely doable.

This is the part number of the spring that was broken on mine: 23311228397. Look here for how it goes together: http://realoem.com/bmw/showparts.do?model=BL93&mospid=47714&btnr=23_0956&hg=23&fg=15

Also, as for changing it yourself, look at this DIY: http://www.m3forum.net/m3forum/showthread.php?t=396595

Make note of the observations I posted at the end. The original author added a lot of unnecessary steps, mostly in the engine bay. Really, you just have to loosen the fan shroud, unhook the air box, remove all of the shields and crossmembers down below. Remove exhaust, drop the transmission crossmember and lower it in the rear until you can reach the plug. It won't be easy to remove.

FYI, the spring only costs a few bucks.
 
#17 ·
It's held in with a steel plug. You just pry it out then push the plug back in after you change the spring. One tip, if the spring is broken in many pieces and doesn't come out on it's own, slide a wood screw in there and the threads will catch the spring and you can draw it out.

Just put the new spring in the roller housing and press the plug back in, then put it all back together.
 
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