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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > M Series > E46 M3 (2001-2006)

E46 M3 (2001-2006)

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  #1  
Old 05-23-2013, 08:57 AM
his15153 his15153 is offline
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Mein Auto: 2001 BMW M3
Engine roughness/vibration

I have a 2001 M3. I have been having problems with an intermittent roughness. The roughness happens both while idling and while accelerating. The revs do no go down on idle however, just the vibration. I have gotten 2 different opinions from mechanics on what the problem could be.

I do get an intermittent check engine light for the catalytic converter. However, the roughness happens with or without that light being on. But one mechanic thinks that may be the problem.

The other mechanic told me that it could be the flywheel. In which case, maybe the problem I am having is not roughness, but just a vibration.

Has anyone had this same problem. Both jobs will end up being pricey, so I hate to do either one on just a whim.
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  #2  
Old 06-11-2013, 07:43 PM
JayMac JayMac is offline
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Mein Auto: what ever starts
Do you have the vibration or roughness at high speed, rpm? If no, I would rule out the flywheel. If it is out of balance or damaged spinning faster would make it worse.

Roughness:

bad gas
vacuum leak
bad o2 sensor
fuel filter


I would try a code reader to see if you can pick up any info. Bad cats wont make it run crappy but will give you a cel. Bad rear sensor wont' make it run crappy but will give you a cel because they tell the ecu if your cats are working. Bad front o2 sensor can cause both.

Start with the simple stuff first.
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Old 06-12-2013, 01:23 PM
his15153 his15153 is offline
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Thanks for the reply.

The vibration seems to get better as the rpms go up, or perhaps just less noticeable.

I did a smoke test and verified that there is no vacuum leaks. I had a code reader hooked up, and the only CEL is for the cat. Not for the O2 sensor. Also, I had the fuel pump replaced a few months ago when I first bought the car, because it was bad.
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Old 06-13-2013, 12:10 AM
JayMac JayMac is offline
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Mein Auto: what ever starts
AS for the cat, it still could be your rear o2 sensor. They are the same sensors just different part numbers due to the length of the wire and the different plug. Your front sensor checks the air fule mix, the rear sensor checks to see if the cat is working. So you could have a bad rear sensor instead of a bad cat. You would want a bad sensor rather than the cat unless you can find a used one. Vibratyion is either loose or out of balance. Do you feel it in the steering wheel or the seat?
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Old 06-13-2013, 09:31 AM
his15153 his15153 is offline
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The more I think of it, the more I feel like it is a vibration and not a roughness. The tach never seems to move when the car starts vibrating, also, I can feel a very subtly shaking when the car is at idle sometimes as well. Also, the vibration is the whole car, not just the steering or the seat.
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Old 06-13-2013, 09:58 AM
JayMac JayMac is offline
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Mein Auto: what ever starts
Simple checks would be motor mounts and transmission mounts. The secret to any of this is to take it slow. Think it over. You know more than you think.

If it vibrates when not in gear that should eliminate some of the variables. You have a high torque engine. If you or any previous owner like to drive your car the way is was designed, some of this stuff wears out. There is only 4 points holding in all that. Two engine two tyranny. You might be able to have someone look while you hit the gas or swap positions and you look. If you let go of the wheel does it shake? Car still go straight? Another crazy test is to find an open parking lot or light traveled road. Get car to @30 mph and turn off the engine, need to have it out of gear and get the key in the position to be able to steer. Windows down, listen and feel. REMEMBER YOU LOSE POWER STEERING AND BRAKES SO PLAN ACCORDINGLY.

Could also be a stuck caliper or warped rotor. Any thing that rotates. Bent rim. tIRE OUT OF ROUND Remember any time you spend on this you would be paying someone else $100 per hour to do the same thing. Good luck! keep me posted.
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