open & close loop - Team Camaro Tech
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post #1 of 5 (permalink) Old Jul 16th, 06, 08:31 AM Thread Starter
Join Date: Dec 2005
Posts: 26
Question open & close loop

what is open & closed loop? how do you go by doing this procedure? i have an 89 iroc and sometimes it cuts off when i'm at a light or backing back. someone suggest open close procedure
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post #2 of 5 (permalink) Old Jul 16th, 06, 09:00 AM
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Re: open & close loop

Open loop is when the car is cold and the O2 sensor has not heated up enough to put the computer into closed loop so that it can take over and make needed adjustments. In open loop the engine runs at full rich with no adjustments being made. IF you have a bad O2 it could keep the car in open loop. As far as this being a repair procedure, its not. It is a status of the computer at a given time based on it's information of its current conditons. To check the car out on a scan tool the car needs to be brought up to tempeture putting the vehicle into closed loop. That is just basic principle as you can get into things like speed density and mass air flow and multiple O2s sensors that are both up stream and down stream etc etc. Is your check engine light on? or on before it stalls? I would start with a scanner to see if you have any stored codes in the computer and go from there. ALso your problem does not need to be computer related. It could be something as simple as the IAS (Idle air control seliniod) that is all gummed up with carbon or the little by pass hole in the throttle body is clogged. You can clean it out with some carb clean. Hope this helps!

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post #3 of 5 (permalink) Old Jul 16th, 06, 10:03 AM
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Location: Tampa, Florida
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Re: open & close loop

Usually you know you are in open loop when the "Check Engine" light comes on after the car warms up.
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post #4 of 5 (permalink) Old Jul 18th, 06, 06:41 AM Thread Starter
Join Date: Dec 2005
Posts: 26
Re: open & close loop

no sevice light is on
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post #5 of 5 (permalink) Old Jul 19th, 06, 05:02 AM
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Location: chicago
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Re: open & close loop

The temp sending unit for the computer (there is one for the dash too) can fail and not give you a check engine. It would create a poor run condition too.
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