Cant seem to find the cause...any idea?

[bsm]

hi, i recently had a CEL for o2 sensor. i used to be getting around 450km on a full tank. after changing the sensor, i could only get about 300+ . later i found out that the sensor was from a different engine.so i managed to get a proper one and thought it would be fine after that. but i could still only go 300+. i know i was running rich during that time coz the plugs showed so, but even after dyno and setting the A/F properly, its still the same. ive checked almost everything else and dont know what else to do. plugs are fine now, no leaks, etc.

the only thing i suspect left now is whether the o2 sensor that i changed could still be faulty. not showing a CEL, but maybe its running in open loop all the time. how do i find out for sure? also, with a piggyback, at what point does the o2 sensor switch from closed loop to open loop?

please help

thanks.

 

[xtremeleo]

it was a good thing u checked and found out the sensor was not a correct unit, bravo. have u reseted the ecu after changing to the proper sensor sir?

 

[bsm]

yeah i did that. then monitored on a full tank. seemed to be going alright the first 100km then after that i could still only get 300+

any idea on the open loop/closed loop thing?

i plugged in a scanner tool at the workshop just now to just double check if there were any errors, coz i heard that its possible for it to be faulty even without a CEL. but either the scan tool wasnt very good or it was incompatible coz it initially said 'ecu id' not detected, continue in 'limited mode'. troubleshooting doesnt show up any o2 sensor codes anymore like last time when i initially had the problem, but on the realtime data list, theres nothing that says o2 sensor. but i did notice on the initial screen of the scan tool there was an obdII selection but somehow we didnt try that.

 

[bsm]

anyone have any idea about my issue?

please help
thanks alot.