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Location:
Melbourne
Registered:
March 2004
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Old or faulty Oxygen Sensor - does it affect idle speed
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Wed, 17 March 2004 05:04
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The idle speed on my ST162 varies a lot -- 99% of the time, it is 100 to 150 rpms below the 750rpm that is steady when the T & E1 connectors are shorted. It is about 200 rpm lower when stopping and starting on a hot engine. The timing is spot on at 10 deg BTDC (with T & E1 shorted). I'm pretty sure it's not a vacuum leak or dirty injectors. Could a faulty or old oxygen sensor cause the erratic idle? The check engine light does not come on, so I presume that it is still sending an acceptable signal to the computer. I don't wanna spend dough on a new oxygen sensor if there is little or no chance that it affects the idle speed.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Fri, 19 March 2004 00:59
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no, i don't believe the O2 sesnor is active for idle mixtures (but i could be wrong  ) check what voltage the sensor is giving, should flick back and forth from 0-1V when the engine is in closed loop mode.
Cya, Stewart
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Location:
Canberra
Registered:
May 2002
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Fri, 19 March 2004 07:25
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I had bouncing idle problems with my ZE which turned out to be an old oxygen sensor..
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Fri, 19 March 2004 09:21
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i stand corrected 
so ben, you are saying that the ECU is in closed loop mode at idle?
anyone have a reference (ie a manual or similar) to confirm?
Cya, Stewart
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Location:
Vic
Registered:
May 2002
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Fri, 19 March 2004 11:33
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I believe the computer uses closed loop mode for idle & cruising.
My 4age popped a bit at idle when the oxy sensor was broken
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Location:
sydney
Registered:
March 2003
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Fri, 19 March 2004 12:36
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yer o2 sensor only works at idle or cruise
thats y these guys how buy cheap ass air /fuel ratio meters dont get correct readings above cruise
i do know on 20vs that it makes em bit better of the mark if o2 meter is connected
had probs with one one day when i fixed it customer said car went bit better off the mark
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Location:
Sydney
Registered:
January 2004
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Fri, 19 March 2004 14:48
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Only open loop on full throttle from all that I've read ... 
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Location:
Sydney (Liverpool)
Registered:
March 2003
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Sat, 20 March 2004 08:10
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My O2 sensor isn't connected at all and my GZE seems to be running fine with no idle problems.
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Formerly TRD_RoLLa
Registered:
May 2002
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Sat, 20 March 2004 08:15
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I had same experience as Juggalo. No real noticeable affects on my fuel economy either.
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Location:
Adelaide
Registered:
May 2003
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Sat, 20 March 2004 11:54
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I get bouncing idle at the moment, but train of thought is that the O2 sensor is dead. I will unplug to test in the next few days.
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Location:
Sydney
Registered:
January 2004
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Sat, 20 March 2004 12:27
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As said by others previously, short the diagnostic terminal if you have one to see if any fault codes come up. Only some of them trigger the check engine to stay on when the car is running. I think in 4age oxy sensor was a code 21 but check for you car.
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I Supported Toymods
Location:
Sydney
Registered:
December 2002
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Re: Old or faulty Oxygen Sensor - does it affect idle speed
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Sun, 21 March 2004 03:03
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your AFM could be getting a bit stuffed... that will cause low idle to the point of annoying vibration.
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