Rough Idling 2001 BMW 330Ci

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  #1  
Old 03-29-08, 02:03 PM
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Rough Idling 2001 BMW 330Ci

My 2001 BMW 330Ci (80 000Mi) started idling rough a few weeks ago, and simultaneously the "check engine soon" light came on. I had the codes checked out, and turned out to be oxygen sensors. The technician said I did not have to replace the sensors unless I need an emmissions inspection, and that they were unlikely the cause for rough idling. Is this correct, and are there any quick diagnostics I should do prior to taking the car in?

Any suggestions most appreciated,
Jan.
 
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Old 03-29-08, 02:11 PM
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Well if you wanna go a cheaper route to try and diagnose the problem, my suggestion would be to replace the spark plugs! I never owned a BMW but I do detail a couple on my side job. Not sure where they are. If you are handy w/ stuff you should have no problem doing this. If you are going to do this you might as well replace the plug wires also. Keep in mind if you do, do both wires and plugs replace 1 plug and a wire at a time. Don't take off all the wires at once b/c you'll mix up the firing order on the distributor. This should be cheaper than an O2 sensor. I had an O2 sensor exhaust sensor replace in my vehicle and it cost me 140 bucks. You should be able to pick up plugs and wires for less. Good Luck.
 
  #3  
Old 03-29-08, 04:35 PM
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I am no expert on newer cars with all their emmission controls, - but I have heard, like on car radio shows, that the sensor listed on a code is not always what is wrong. In the case of an oxygen sensor where say a car is running poorly, the entire fuel mixture may become screwed up, even over one misfire in one cylinder. This then would affect the exhaust gases.The oxygen sensor, in the exhaust system, then is perhaps seen by the computer to be the culprit, because of it's inability to correctly correct that bad exhaust. When in reality it is not due to any malfunction of the sensor. That the actual malfunction came from some other problem upstream.

Sensors in furnaces, and I'm sure many other solid state/computer devices, have these same shortcomings. I recently mentioned in the gas heating forum that I had a gas water heater's code tell me the pressure switch was at fault, but it really wasn't. The problem was the pressure switch was not even recieving voltage, due to a problem upstream! (like as stated above).

Therefore, perhaps a bad plug, wire, cracked insulator on a plug causing carbon tracking or an inadvertant ground-out, could be causing a misfire, which in turn causes bad exhaust, which in turn causes the O2 sensor to be blamed for not being able to properly correct the mixture. Something like that, anyway.

Whenever a person has poor idle, misses going on, etc., one thing a person can do is go out there in the dark and when the engine is running, see if you see sparking going on under there. (You should not see any)
 
  #4  
Old 09-06-09, 06:01 AM
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You are right!

Thanks for the reply. I took it to the dealership. The problrm was a leak in the intake manifold / DISA valve????.

Anyway, thanks again for your reply!
 
  #5  
Old 09-06-09, 07:35 AM
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You put up wityh the problem for like 1 1/2 years?

It's nice that you got back with us and this can help other people. Bottom line is oxygen sensor code was not the oxygen sensor, right?
 
  #6  
Old 09-07-09, 05:34 AM
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That's correct! Thanks again.
 
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