open loop? close loop?

[tcfco2005]

i hear and read about this alot but i dont know what it is refering to. can someone fill me in...thanks

[Hypsi87]

when your computer detects a cold coolant, and a cold air temps, it goes into what is called open loop.
Open loop refers to the o2 sensor circuit. The computer ignores the o2 circuit and "opens" the circut and injects fuel based on a cold engine fuel map. When the coolant temp gets warm enough, the computer then "closes" the o2 circuit sensor and uses the sensor to more accuratly deliver fuel.

When you are in open loop, o2 sensor is not used and you are injecting rich ammounts of fuel.

in closed loop, your 02 sensor is read and your fuel dilevry is more accuratly monitored and controled.

[tcfco2005]

thanks man ive been wondering that for a while now

[supervisor1886]

I have aquestion here. Would that be possible to run open loop even when the engine is hot without having any codes on the computer. I suspect this, because my 2.8MFI gas mileage can be compared only to a 5.7 tpi one.? Funny? The car runs fine, no signs of rich exh., new pump, new fuel filter.

[Hypsi87]

Originally Posted by supervisor1886

I have aquestion here. Would that be possible to run open loop even when the engine is hot without having any codes on the computer. I suspect this, because my 2.8MFI gas mileage can be compared only to a 5.7 tpi one.? Funny? The car runs fine, no signs of rich exh., new pump, new fuel filter.

yea if your PROM has the programming in it.

My PROM program is set to go into open loop at idle because if my torque converter. With my loose converter (3300) it helps it with idling.