My AFR dropped to 10.2 in WOT last night. When I talked to STM a few months ago they said its okay to be around 10.6 which is the lowest it has ever gone until last night. I have had previous posts about power issues...could this be affecting my spark causing it to run rich? I have less then 500 miles on my plugs same as oil. I appreciate any advice on the situation...my evo is really fristrating me lately.

 

Yah thats too low.... Do a boost leak test, that can cause afr to do that.

 

I've never done a boost leak test I have no idea how to go about it..I'm still hitting what its tuned for at 27psi

 

Yah you will still be able to make boost, its just more work for the turbo and a loss in power. There are many guides on this site on how to do a boost leak test if you look for them.

 

Are you on ngk copper plugs?

 

Op your tuner is right but you have boost leak,your lowest should be 11.2.its still safe what you got but still you have boost leak.

 

I'm using NGK Iridium plugs. I'm going to do a boost leak test later on today see if I can find anything

 

So at this point there is no boost leak.

 

hmmm, maybe a O2 sensor going out?

 

You picking up any knock? Too many counts of knock will put you onto the low octane maps, which could be pretty rich. Also what are you LTFT low and LTFT mid?

 

My 02 sensors are deleted on the tune so could that still cause the issue? I dont hear any knock it still runs fine just very rich...and im not sure what LTFT is or how to get that off my car?

 

ltft stands for long term fuel trim. If it was your oxygen sensor, it would cause the ltft to be out of normal range. This is usually accompanied with a check engine light though. The rear 02 sensor is usually what is deleted. The front one is needed for scaling injectors, and closed loop operation.

 

Ohhh makes much more sense now. But fortunetely i dont have any check engine lights on right now atleast.

 

Without any scanning equipment it would be kinda hard to verify if the fuel trims are effecting your tune. You could do an experiment though that would be helpful. Go do a WOT pull and note the AFR. Then pull your negative battery terminal for ~30 seconds to clear your learned data off your ecu. Then go do another WOT pull. If the AFR's are significantly different, then that would indicate the LTFT's are messing with your tune.

 

Alrite ill give that a try and post my results