12.6 air fuel ratio too lean? causes?

[speedyz2]

Hello,
I was reading through the air fuel ratio posts to try to find something similar to mine and I found that most of the posts were about hooking up a gauge and I didn't want to hijack a thread.

I recently had my motor rebuilt (around 3k on it right now) and my ratio is at 12.6 at 5500RPM's. My car is completely stock and I was wondering whether this is good or bad. A few of the posts I read said this was extremely bad and others said it was fine. My mechanic said that his 1g runs around 11 and he's not sure if the 2g's are supposed to be higher or not. Basically I'm wondering if I have a problem somewhere, because I REALLY do not want to break anything considering the money just spent to rebuild it.

I've looked into getting new injectors/fuel pump/ecu but I'm not sure if it's needed. Any help is really appreciated. The car runs great and other than the lean 12.6 there are no other problems. Thanks.

 

[Colt4G63 also]

Is that 12.6 what your wideband says at WOT? Because that sounds too lean for pump gas. You don't have any mods listed, so I would assume that it should be running stock mixture which would probably be around 9:1 AFR at WOT.

 

[MY1GDSM]

How much boost are you running?

 

[zhjiln]

fire that mechanic.... its not car to car that run different AFR .... its just a rule ... N/A cars can run 13 ish safely ... forced induction cars need to be at 10.5-11.0 at wot

check your fuel system ... injectors, fuel filters, lines.. etc

 

[speedyz2]

Thank you for the quick replies.

My mechanic hooked up his wideband and it read the 12.6 running on regular pumpgas (93).

Boost is at 12.

To my knowledge the car is completely stock, except for a K&N FPIK.

Any ideas on parts to replace or what to look for would be appreciated. The car has had a boost leak test done also and everything came out fine.

Thanks guys/gals!

fire that mechanic.... its not car to car that run different AFR .... its just a rule ... N/A cars can run 13 ish safely ... forced induction cars need to be at 10.5-11.0 at wot

check your fuel system ... injectors, fuel filters, lines.. etc

thank you for the clear-up. unfortunately he is the most knowledgable DSM mechanic in my area.

I believe that the injectors/pump are original, although I cannot be 100% sure. I'll look into buying some. Do you think used stock injectors/pump would be ok or do I need to get brand new? Thank you again.

 

[Rob10_99]

Your tech is a moron.

He needs to go back to school or at least get an ASE before he works on your car again.

 

[speedyz2]

Your tech is a moron.

He needs to go back to school or at least get an ASE before he works on your car again.

Unfortunately it's him or the dealership and I do not have the money for the dealership. He's better than the last guy I had as well .

 

[Rob10_99]

FFS find someone local even someone from the board to work on your car. Sounds like you live in V8 ville.

 

[speedyz2]

FFS find someone local even someone from the board to work on your car. Sounds like you live in V8 ville.

Yep it's kind of secluded up here. Other than a new mechanic do you know what I could possibly take a look at to replace? I know zhjiln mentioned fuel system, is that the most likely culprit? Thanks again guys.

 

[Colt4G63 also]

I wouldn't just go throwing new fuel systems at it. You need to test it and see why it isn't getting enough fuel. It might be a problem elsewhere that pevents it from accurately measuring your intake air and/or properly using that information. Does it only go lean at 5500 RPM and then back to 9:1 or 10:1 above and below that RPM? Do you have a log, does your tech know how to diagnose things like that. If you keep running it that way, you'll melt your pistons and need a new engine.

I would read the data from your MAF and MAP, and watch your fuel pressure under boost. See if anything looks out of whack on those tests first.

 

[EclipticalGS]

clogged fuel filter can give lean conditions at higher rpms. just replace it anyway, might as well, its always a good thing and its in an easy spot by your charcoal canister

 

[Rob10_99]

clogged fuel filter can give lean conditions at higher rpms. just replace it anyway, might as well, its always a good thing and its in an easy spot by your charcoal canister

I was thinking the same thing. Get a logger too, its a good diagnostic tool.

 

[speedyz2]

I wouldn't just go throwing new fuel systems at it. You need to test it and see why it isn't getting enough fuel. It might be a problem elsewhere that pevents it from accurately measuring your intake air and/or properly using that information. Does it only go lean at 5500 RPM and then back to 9:1 or 10:1 above and below that RPM? Do you have a log, does your tech know how to diagnose things like that. If you keep running it that way, you'll melt your pistons and need a new engine.

I would read the data from your MAF and MAP, and watch your fuel pressure under boost. See if anything looks out of whack on those tests first.

From what I was told it goes down to around 11 at lower rpm's. He did not test it above the 5500. He said that things look ok and did not know why it was the 12.6.

I'll change the fuel filter and see what it does. I know I need to get a logger, been looking for one, but money is tight right now .

 

[nikkeebabee]

What is being used to measure AFR's??? Where is the sensor located???