bad o2's?

[luckythirteen13]

when its really cold outside (30's-40's) my car runs really lean untill it warms up. the main problem is when i drive a short distance (10min trip) and then park and go into a store, 5-10min later i get out and start the car and it runs insanely lean. usually about 20:1 but some times ive seen the wide band say as low as 40:1. after about 2 minutes letting it warm back up, its like some one throws a switch and afr goes to 14.7:1 instantly. its not a slow return from 20-14.7 it stays at 20 then instantly goes to 14.7 and then its fine for the rest of the trip. same o2's that were on the car when i bought it 2 years ago. they look in descent shape. i have a narrow band gauge on the left o2. not sure if its the gauge or the o2 thats bad but for the first 10 min of the trip the gauge reads no movement at all. it will stay pegged at lean or rich. what do you guys think?

 

[HISSIN50]

Not that it is the case here, but when the ECT is seeing temps around 160-170*F, in theory, the puter can lean out. The puter knows the engine is hot, for all intents and purposes (no choking is needed), but the leanness causes the motor to heat up. Then once up to 180*+, the air/fuel gets closer to stoich.

I dont know if that in any way relates to anything you have observed, but it was worth mentioning.

Good luck.

 

[luckythirteen13]

this is a more recent problem so i dont think thats it. also, i think i could be getting better gas miliage which is another reason i thought o2's. i get 14-15mpg city driving, no freeway at all.