Would there be any reason why my AEM wideband is reading --- at idle? However when I turn the car on it'll be @ 15.6-16.4 then about a minute later it goes super lean.

I pulled the MAP for my stock tune and it says it should be at 14.7 with 10% engine @ 500 rpm. Does anyone else have the same gauge with these readings?

 

At idle at full operating temp, the car does not run off the fuel map but is run using 02 feedback to always try and hit stoic (14.7:1)

If the wideband is hooked up correctly and still reading full lean at idle I would look at your fuel trims and front 02 sensor voltage (or lack of). I would also check to see if the wideband sensor is good. What kind of readings are you getting at WOT?

 

I get proper readings @ WOT around 10.6 @ 4k WOT which sounds about right for a stock tuned Evo's ecu. The wideband is hooked in to the turboxs bung right before the cat and it appears to read correctly @ WOT. That being said a shop wired it up so I'm sure the connections are together.

I just bought the wideband and it was brand new so I'd hope the sensor was good, although that could be the problem.

 

Are you running upgraded injectors? have you checked your fuel trims recently?

 

Mods: Downpipe, catless, catback exhaust, ARC intake. Everything else is stock other than suspension work.

I'll pull them to check again. If my sensor were damaged would it read at all? The other weird thing is @ cruise its around 16.3:1 and jumps to 15.3:1.

Do you have aim? I hate to be a burden but I'm getting a little worried that its more my car than anything else. There's no engine check light BTW.

 

Well if the fueling was really that lean your car would idle like crap. How is the idle?

I vote for something up with the wideband as your cruise will not be 16.3 with normal closed loop fueling.

 

idle isn't rough at all, and I popped the hood to see if the engine was shaking and its not. I think there's something wrong with my sensor, could it be burned out? or could it be the wiring?

I could always get another bosch sensor and plug it into the downpipe again.

 

How old is the sensor and did you ever run it in the exhaust stream unpowered?

 

Brand new, and for the time it took to drive to the shop from my house. Yes.

 

Yes you did run it unpowered?

 

Yes, I did run it unpowered.

 

I'm with Razor ... heated sensors hate being run cold and foul quickly. That could be your issue.

Before leaping and buying a new one, log the fuel trims. If they are within 10% or so your idle/cruise AFR should not be that far off and it's likely a sensor issue. It could be the WB or the NB though.

Do you have a CEL? Have you logged the stock O2 sensor #1 to see how it's responding? It should aim for .5v in closed loop.

 

This will kill the sensor quite quickly.

 

ahh ok thanks for you help razor, just to make sure when you say unpowered you mean without the gauge plugged into the ground and 12v eco slot correct? I.e. the gauge was off but the sensor was plugged in.

 

Well thx guys for your help. After all of your efforts I think I've figured out that it's my downpipe it may need a new donut gasket. The current one is most likely leaking causing the ecu to lean out the car.

Did a test at a friends shop with both my wideband plugged in and a dyno sensor in and they were getting the same readings. Thanks.