last night, while driving back home from work. i noticed that almost every time i come to a stop, my afr gauge is showing 12.3-13.5. it will eventually go up to 14.7-15. wtf??

those of you lucky enough to have rev hang issues on the evo x also kno that 12.3-13.5 is what the gauge shows when the engine is rev hanging. i'm wondering if my fuel injectors are faulty. or perhaps my fuel pump. or it can be the ecu constantly wanting to shoot fuel in to the engine for no other reason than to waste gas.

is this a precursor to something horribly going wrong under my hood? or is it due to the recent change in climate (getting a lot cooler here in s. ca)?

the car seems to be running fine. if anything, due to the cooler climate, it's pulling even stronger now.

oh, i do have the triangle of death but it's not the time chain. i pulled the code and it had something to do with the throttle body. possible culprit?

any insights will be appreciated.

 

Mine does it too. There was a thread on one of the forums a while back discussing it and from what I remember most people think it's because there is so little air flowing through the exhaust when you come to a stop. It takes a long time for the leaner air to make it's way past the sensor. If you tap the gas it should go back to normal sooner.

 

but consistently on every stop? it didn't do this before. before, the second i come to a stop, my afr reading showed 14.5-15.5 and the numbers would change frequently, like it would fall within the 14.5-15.5 but the numbers would change 2-4 times/second. now, it's realllllllly slow. sort of like a countdown. it would go from 12.3 to 12.5 in 3-4 seconds.

this is what happens now when i come to a stop:
-driving in 4th around 35mph.
-coming to a stop so applying brake.
-when rpm comes down to about 1.5k-2k rpm, i pop it out of gear and start coasting to a stop.
-come a stop and the afr is showing something in the 12-13 afr. the car is still idling at appropriate rpm (a little below 1k).
-slowly, the afr will move up to 14.7 (stoich) but it takes a long time. i timed it this morning and it took almost a full minute for it to reach 14.7-15.3 from low 12's.

 

I have the same problem but on an evo IX. I also get throttle hang sometimes where the car idle just raises on it's own from 1k to like 1500rpm for no reason. I have to turn the wheel slightly to get the load on the engine to pull the idle down because it's annoying to sit at a stoplight with a high revving loud rice burner...

 

i didn't realize this issue plagued the evo 9 as well. so you guys don't have a fix for this either?

 

By chance; have the gas companies i.e. oil refiners in your area changed from their summer blend to winter blend?(additives, composition is different) and the car is trying to adjust. If your car is tuned, contact your tuner to see if he has any ideas.

Also, maybe you should run couple tankfuls of a different brand of gasoline to see if there are any improvements.

 

yes, it seems as though they've changed it to the winter blend already but this didn't happen last year.

i was planning on contacting my tuner last weekend but didn't get a chance. i'll be reaching out to him this weekend.

 

so today was nice and sunny here in ca (77-88 degrees). i noticed my afr is now reading normal. normal as in when i come to a stop, the afr shows 14.5-15.5 without hovering around 12 for the first 10 minutes.