hey guys, just bought an evo. it has a zietronix gauge and everytime i get close or go wide open throttle the afr gauge reads what it should, but then immediately goes fully lean to 21. obviously it isn't going to 21 because when it does it pulls just fine. tried to search but couldn't find anything. if anyone knows that would be cool, thanks!

 

Pull it out and check if it's covered in crap.

 

zeitronix user here..can you give more details? 21 afr meaning when you let off throttle?

 

When you close throttle ECU cuts spark and fuel.
If you are seeing AFR at idle in 21s then you have an exhaust leak.

 

when you let off the gas, like coming to a stop... it will get up there to 21 just like Zeitronix said. nothing out of the ordinary unless you get that reading while your not moving. I have the LCD option. LOVE IT.

 

no no no, let me reiterate. WHILE i am at full throttle. sorry it sounds like a typical noob question. but as i am at full throttle it does what it should, then spikes straight to lean (which is the max of 21 on zietronix). i'm sure it's not going 21/1 afr because it pulls great it's just as the title says. lol, being weird.

 

oh man, it should NOT spike at 21 afr at WOT..it will feel strong but it will sooner or later melt things..have it checked first..you "may" have a huge exhaust leak pre o2 sensor..probably o2 housing gasket..if not faulty o2 sensor, but i'd suggest look at a possible exhaust leak first..

 

I'll give you the real answer:

It is possible you have an exhaust leak like tonyboy said.

If not that the more likely answer is the sensor is bad and you need a new one. This can happen from overheating (too close to the turbo), using leaded gas, driving the car with the sensor installed but the sensor heater off/unplugged, or just being old.

 

Sensor is bad. Replace it.

 

^^^^ that's what i was thinking. just wondering if anyone has ran into it before. thanks guys!

 

How long a sensor should be good for??? Basically what's the lifetime of it??? I was wondering...


Thanks,

 

Bosch call out 160K, on a stock car. But realistically on a running rich, hot turbo car it lasts 30-50K if you treat it right.