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Discussion Starter #1 (Edited)
Already tried the search function, this problem seems to be slightly different than what most people have.

2001 330xi w/ 96k

The issue is that on a cold start (35F the other day) the car will shudder while driving until the engine heats up (cruisin at about 30 mph in 3rd gear at 2000rpm shuddering is at its worst). Contrary to most people's posts, at idle its perfectly smooth and quiet; I only notice the problem when the engine has a load on it (as soon as I take out of gear the shuddering goes away). Also, as the engine temp warms up the problem completely disappears. I just replaced the fuel filter (shuddering was there before and after) and the spark plugs were replaced 10k ago (as well as a swapping of the ignition coils to address a rough idle). Also, filter service and oil change was done 3k ago.

Problem fixed (I think) by replacing pre-cat 02 sensors. Most likely that a heater in one or both of the old ones was broken so they wouldn't operate optimally until engine temp was high enough.


-Mike
 

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Discussion Starter #3
do u let the idle drop when u cold start? it takes a about a minute to drop from ~900 to 500
Yes. The idle drops fairly quickly (about 30 seconds), and it takes me about another 45 seconds to drive to main road where I accelerate to 30mph and I begin to notice the shuddering.
 

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Discussion Starter #5
Most likely solution - replaced the two pre-cat O2 sensors the other night and at the same time cleaned the MAF. Although it wasn't as cold this morning (about 45 degrees) absolutely no shaking/shuddering was noticed. This makes me think that it was most likely a heater in one or both of the O2 sensors that had failed, so the sensors wouldn't work properly until engine temp was high enough.
 

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Discussion Starter #7
about $110 for both of them i think. I bought them from autohausaz. Pretty sure their price is better than pelican and a few other sites, and you get free shipping.
 
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