so recently, (as the climate got colder) i noticed my afr reading has been a little different. car seems to be running fine.

for starters, the reading is a lot slower. another member pointed out that if i have a leak in the exhaust system, (ie dp) it can cause a slower reading. before, the aem afr gauge would change numbers several times/sec. now it reads a lot slower (numbers change gradually).

coasting at 40mph in 4th gear, the afr will show anywhere from 14.5-15.5 (normal). once i let off the throttle, afr goes to ---. but then when i come to a stop, the afr will change from --- to 11-12.5 (aka rev hang). the car is still idling below 1k rpm like normal. it takes a good minute for it to go back to stoich.

now, it's just getting worse. last night on my way home, as i was coming to a stop, i looked at my afr and it showed ---. i was expecting it to shoot up to 11-12.5 again as usual. but this time it just stayed at ---. and yes, i was sitting at a light idling and the afr is showing ---.

at this point, i'm guessing/hoping that nothing is wrong with my car, but instead my aem gauge reading is off. i'm going to try and go see my tuner soon but if anybody has experienced something similar, please let me know.

 

That was how my sensor acted before it died.

 

Mine started doing that the other day. I approached a stop light and put it in nuetral and it would show --- for a good 5-7 seconds before eventually climbing back to the normal idle reading.

Im not sure if the sensor is starting to go bad also, but I have to send AEM my oil pressure sensor that lasted a whole 30-45 days before taking a poop on me. And if my wideband sensor is starting to go, then it means it lasted a whole 6 months.

 

I'm thinking is too lean.

 

this is what i'm hoping for.

 

the car is running fine. i think...

afr reading at wot/cruising is still the same/on point.

 

Bad sensor or an exhaust leak before the sensor

 

It's been cold lately. That can cause a boost/vacuum leak which will cause you to suck in unmetered air at idle, making you truly run lean at idle (but usually rich at WOT, too). If you rule out the sensor, a BLT should be on your list.

 

this sounds scary...

 

What sensor are you using? Sounds like its on its way out.

 

Sometimes there isn't enough exhaust flow on idle to get a proper reading. It's more normal if the sensor is further downstream. Sensors do tend to show lean when they're on the decline, too. As far as going -- on decel, that's perfectly normal. There shouldn't be any fueling on decel, so it'll show lean. Regardless, it's just a common sensor issue. No worries.