user name001

This morning i hooked up my scan tool and watched some live data, first start of the morning and it went right into closed loop. shouldnt it have gone into open loop till it warms up? it will go into open loop when WOT, but why is it immediatly in closed loop upin start up? Heat gauge is where it should be and CTS was replaced.

2000 se AUTO
190,000 kms.

Thanks.

user name001

Is this correct at least.. maybe i have it wrong

open loop- warmup; 30 seconds to a minute until O2 sensor is heated, once warm it goes into closed loop.

Closed loop- when vehicle is warm @ idle, accelerating (minus WOT) and cruising, is this correct?

SurraTT

iTrader: (59)

I'm not sure how long the "warmup" time is for the stock ecu. But the way its doing should be just fine. Itll add fuel anyway till the coolant temp comes up in closed or open loop.

Amerikaner83

iTrader: (17)

Why are you worrying about open/closed loop?

user name001

because as soon as i start my car when its cold, its in closed loop, it runs like crap when cold, hesitating in the lower rpm range(1500-2000rpm) and sometimes hard to start. im not getting a open loop warm up period like i should. My car stays in closed loop unless im at WOT or cruising at higher speeds with no throttle, thats the only time i see an open loop.

Amerikaner83

iTrader: (17)

ok, that makes sense as to why you're looking into it.

I would tend to agree with you, that open loop warmup period isn't correct. Have you made any underhood changes recently? Closed loop at startup tells me that i'ts running pre-set for some reason...i.e not getting a signal value it's expecting to see.

user name001

The only underhood changes i have done have been to correct this problem befor i realized it was an open loop/closed loop issue.
ill start by saying i have no codes, i have cleaned the following- IACV, TB,MAFS, and replaced the following- MAFS, TPS( caliberated properly as per fsm) plenum gasket, CTS, TCM, fuel pump and strainer, FPR, PCV, plugs and filter,and a few other things i may have forgotten.

I have tested the following- MAP sensor,CPS CKPS( both) fuel pump after replacement, coils.

this was all done over the past 6 months to try and correct the problem befor noticing today that i dont get an open loop at start up. it will show open loop on both fuel trims with acc. on, but as soon as i start my car it immediatley changes to closed loop. im assuming that once the vehicle is started it thinks the engine is at operating temp. when infact, its not.

Thanks!

Amerikaner83

iTrader: (17)

does the temp. gauge operate properly? You changed the CTS...that's the Coolant Temp Sensor, right?

user name001

Temp guage seems fine.

Yes, CTS (coolant temp sensor) was replaced.

what else would determine closed loop vs. open loop?

Amerikaner83

iTrader: (17)

Ooh boy...you're gonna have to get deep into the FSM on this one.

The ECM determines open loop or closed loop based on a variety of factors...

WAIT!

http://forums.maxima.org/general-max...-question.html

hmm...

edit...you CLEANED the IACV, yes? Maybe it should be replaced? I remember reading somewhere that sometimes with the 5.5gen the ecm gets fried due to coolant somehow...? Don't quote me on that one.
http://www.automotiveforums.com/t883...ny_ideas_.html

another edit...bad TPS? Open/closed loop is controlled y TPS according to this thread:
http://forums.maxima.org/supercharge...-tuning-2.html I know you said it was calibrated properly...but maybe not?

user name001

Ok, well tonight i will read through the FSM and see what i can come up with.. yes, i did clean the IACV . i actually called nissan where the vehicle was originally purchased from when i bought it 8 mnths ago ( the previous owner was the head service advisor of that location as well) and asked about a tsb, she told me the IACV was replaced under a tsb ?? i found that odd. but apparently it was replaced, mind you that was 10+ years ago. the reason i did call was because of the known ECM issue.

thank you for your interest in my issue im having. i am working right now but i will read over the FSM tonight and the links u posted and post back my discoveries!

thanks amerikaner!

SurraTT

iTrader: (59)

Unplug your primary o2 sensors. And see how your issue is.

user name001

Ah! good idea! that would keep it in open loop! ill give that a try as well!

Thanks surraTT!