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-   -   M3 E46 poor acceleration (http://forum.e46fanatics.com/showthread.php?t=957192)

kaym3 11-21-2012 08:00 PM

M3 E46 poor acceleration
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

JTripper 11-22-2012 08:21 AM

Seafoam that biatch!!!

DesiredM 11-22-2012 08:43 AM

Try turning your dsc off

bobm3 11-22-2012 11:33 AM

i think your motor is going into limp mode
car wont go past the 4 to 5,000 rpm.. you should go have your car look at for a tune.. it is not a big problem.....
bob :thumbsup::thumbsup:

illestminimike 11-22-2012 03:43 PM

Any lights on the dash?

kaym3 11-22-2012 06:03 PM

I get the cog light on sometimes when it wont rev out, the dsc makes no difference. Is there an ecu connected to the hydrauliic pump on the smg?

illestminimike 11-22-2012 06:09 PM


Originally Posted by kaym3 (Post 14920220)
I get the cog light on sometimes when it wont rev out, the dsc makes no difference. Is there an ecu connected to the hydrauliic pump on the smg?

Yes there is. Ok you really need to get someone to read the codes for the SMG Cog light. Do that and report back.

kaym3 11-25-2012 04:48 PM

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?

roadtrip1098 11-27-2012 02:16 PM

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.

roadtrip1098 11-27-2012 02:17 PM

Should also note that a faulty salmon relay can also cause the duty cycle incomplete, but most likely it's a battery issue.

hoonpv 11-28-2012 04:02 PM

Looks like your pump is on its last legs. $$$$$$$ bend over bro!

Forcfed93 11-28-2012 04:30 PM

Sounds like a compression spring. Does it skip the gear after being unable to select it?

You'll probably get a code saying "gear not selectable".

The spring is kind of a PITA to replace (I did it in mine), but it costs less than $5.

screamer-beemer531 11-29-2012 09:50 AM

God I hate when these kind of issues pop up and it could be anything out of hundreds. I hate it more when it doesn't give you codes. I too say check the compression spring and keep us posted.

kaym3 11-30-2012 08:16 PM

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.

Forcfed93 11-30-2012 08:29 PM

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?...56&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.

kaym3 12-01-2012 05:05 PM

It shows two springs in the diagram did you only change the one and can you tell me how it comes out or is held in as I can't quite make the diagram out, thanks

Forcfed93 12-03-2012 01:10 PM

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.

kaym3 12-08-2012 02:50 PM

Thanks guys for all the advice please keep it coming if you have any more. I,m going to replace the gear change sensor and compression springs as soon as and I will let you know.

Forcfed93 01-08-2013 01:34 PM

Have you had a chance to get this resolved? I'd like to know what the outcome was.

kaym3 01-09-2013 06:10 PM

Hi, I am awaiting the parts from bmw and access to a lift as i don't fancy doing it on my back with ramps. I will let you know when I have done it and the outcome, cheers.

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