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#1
Apr 17 2014 11:54pm
I hate taking my car to a shop without having an idea of what's wrong with it ahead of time, so any help is appreciated.

On cold start-ups, I get some engine knock, and overall just runs rough for about 5-10 seconds. It revs up a bit on it's own (~1700), then calms down and seems fine.
After driving for a while, then coming to a stop, as I slow down I can see the tachometer drop very quickly, down to 300 or less, and sometimes just stalling out completely. The longer I drive between stops, the more likely it is to happen.
Check Engine Light on, OBD2 reading indicates bad O2 sensor/system too rich.
Overall notice a general loss of power.

05' BMW, 85k miles

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#2
Apr 18 2014 12:01am
"Check Engine Light on, OBD2 reading indicates bad O2 sensor/system too rich."

why exactly do you need another diagnoses when it already told you whats wrong?
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#3
Apr 18 2014 12:03am
Quote (Subwoofer @ Apr 18 2014 01:01am)
"Check Engine Light on, OBD2 reading indicates bad O2 sensor/system too rich."

why exactly do you need another diagnoses when it already told you whats wrong?


I wouldn't particularly expect that to cause issues on cold start-up.
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#4
Apr 18 2014 08:57am
Sounds like a typical cold start to me. Engine needs to warm up and let the metals expand and get back into proper tolerances. You're right, O2 sensors shouldn't cause cold start issues because they aren't inputs in open loop.

Your stalling issues are definitely stemming from that bad O2 sensor though. It's sending rich biased signals and the short/long term fuel trim are going to try and compensate by cutting fuel when in actuality it's already running lean.
At the very least, your car needs an O2 sensor.
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#5
Apr 18 2014 10:52am
Quote (SlyGoSu @ Apr 18 2014 10:57am)
Sounds like a typical cold start to me. Engine needs to warm up and let the metals expand and get back into proper tolerances. You're right, O2 sensors shouldn't cause cold start issues because they aren't inputs in open loop.

Your stalling issues are definitely stemming from that bad O2 sensor though. It's sending rich biased signals and the short/long term fuel trim are going to try and compensate by cutting fuel when in actuality it's already running lean.
At the very least, your car needs an O2 sensor.


probably wouldnt hurt to have the cat converter checked either while its in the shop.
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#6
Apr 18 2014 11:53am
Just buy a corvette
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#7
Apr 18 2014 03:59pm
Lol

Listed the problem. Not sure why car is acting up.
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#8
Apr 18 2014 04:43pm
Quote (SlyGoSu @ Apr 18 2014 09:57am)
Sounds like a typical cold start to me. Engine needs to warm up and let the metals expand and get back into proper tolerances. You're right, O2 sensors shouldn't cause cold start issues because they aren't inputs in open loop.


100% not typical cold start. Maybe my descriptions wasn't good. There is very distinct engine knock, like a thud that you can hear, typically about 3 seconds after starting up. This didn't happen the past 2 years, but is happening now.
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#9
Apr 18 2014 04:45pm
Quote (sarge799 @ Apr 18 2014 05:43pm)
100% not typical cold start.  Maybe my descriptions wasn't good.  There is very distinct engine knock, like a thud that you can hear, typically about 3 seconds after starting up.  This didn't happen the past 2 years, but is happening now.


Get the 02 sensor replaced and go from there. Process of elimination.
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#10
Apr 18 2014 04:58pm
100% of my vehicles make a chattering
type noise when it's freezing out and I start it.

Going to go with : what is thick cold oil ?
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