Crusing afr?

[4doorboost]

so my car usually cruises around at 14.7 give or take. once in a while it will just switch and at part throttle usually under 20% it will just cruise down the road running lean like 17+. when i give it a little gas the afr will improve and at wot its always fine. so if im gradually accelerating it will be at 14.7 then when i back off or just keep my speed constant it will run lean. then all of the sudden it will (switch back) and it will run at 14.7 like its supposed to. sometime it runs lean on cruising for a day or a week before it snaps out of it. seems like only electrical issue would cause it to go back and fourth.. any ideas on y it would do that. usually its when im on the freeway constant speed it will be lean afr's, only constant speed. when i accelerate it goes right to 14.7. any help appreciated

 

[4doorboost]

im thinkin that it has something to do with closed loop? not to sure, could it maybe be my o2 sensor?

 

what are you using for tuning your fuel trims? and what are your settings. sounds like your values are completely out of wack.

 

[4doorboost]

i use an safc2 that was tuned by RRE so i know the low throttle settings are correct. it will be fine a a lot of the time then randomly will be like this for days or weeks then randomly will switch back to cruising at 14.7

 

[4doorboost]

also when it does this my idle seems to be richer than normal like 13.9 ish

 

sounds like your fuel settings are all out of wack. rre or not. i would reset your ecu and redo your fuel trims. your running pig rich and pig lean. what are your mods, and injector size?

 

[4doorboost]

you dont understand.. it will be fine 14.7 idle and 14.7 cruise at low throttle %. then randomly without me changin anything it will run like this.. then in will snap out of it and run fine again.. the tune has never been touched. y would it do this? o2 sensor, im thinking it has something with it running closed loop when im cruising but not really sure

 

[4doorboost]

i have a 8.5 aluminin bottom end. 272 cams, evogt16g, i believe im on 750cc injectors and a walbro 255, and obviously all suupporting mods.. intercooler ect.

 

[bazeng]

14.7 to 1 is fine for cruising mate.... As for 17:1, is that on decel? Off throttle your injectors may be turning off which is also fine. We call that injector over run. Im not that knowledgeable on stock ecus but I've just been tuning my motec at 14.7:1 on cruise and it loves it. Injector overrun is also enabled which stops the rumble and popping.

 

[4doorboost]

my injector over run is on, but the problem is this isnt under decel, it when im cruising at a constant throttle % when i accelerate it goes closer to 14.7 but right when i hold the throttle constant usually under 20% since im just keeping my speed on the freeway it leans out around 17... on decel i see 21 afr. like i said it does this for weeks at a time then will snap out of it and under the same conditions it will cruise at 14.7 from this switching it seems to me like it has to be a sensor or maybe a sensor or wire is geting the wrong voltage..

 

[4doorboost]

so i have an idea, could an exhaust leak cause the car to run lean while cruising. the exhaust leak would have to be before the wideband o2, but would a little leak cause lean condtions while cruising because when i give it a little gas it goes to 14.7. my only other thought would be the o2 sensor in the o2 housing. looks pretty white, and its been years since its been changed.