Opne vs. Closed Loop
Thread Starter
Joined: Feb 2008
Posts: 1,265
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From: Bolton Masshole
Opne vs. Closed Loop I know it has to do with the o2 sensors. but thats about it. What is the difference, and which one is controlling the A/F ratio when? Im trying to figure out if my o2s are the reason my car has a low rpm stumble. How do i figure this out? Thanks guys
Teching In
Joined: Mar 2007
Posts: 41
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From: Tampa, Fl
open loop is when the ecm is running off the ve tables and pretty much ignore the o2's. in order to hit closed loop you have to have three things happen. o2's need to read so much mv. engine temp needs to be so much. and a certain amount of time needs to pass with the engine running. once in closed lp the o2's come in to play.
Joined: Jul 2007
Posts: 2,861
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From: Ringoes/Flemington, New Jersey
open loop is when the ecm is running off the ve tables and pretty much ignore the o2's. in order to hit closed loop you have to have three things happen. o2's need to read so much mv. engine temp needs to be so much. and a certain amount of time needs to pass with the engine running. once in closed lp the o2's come in to play.
closed loop = o2s, tps, coolant.
your car ALWAYS starts in open loop no matter what
TECH Senior Member
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Joined: Oct 2006
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From: Decatur, TN (N-W of Athens)
Don't know about PCMs, but on ECMs no certain time frame has to be met. I've let my car sit for awhile, but not enough that the coolant temp in the motor had dropped below the Closed Loop thresh hold, so I've started it up and it's gone right to Closed Loop.
