Lean AFR when cold

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Lean AFR when cold

Postby warracer » Wed Apr 08, 2015 11:09 pm

Okay,

Im having an issue with my st185. When the car is cold, the afr is extremely lean. We're talking 16-17:1 afr when cruising, but as soon as the coolant temperature neddle move ever so slitghly, im back to steady 14,7:1 when cruising and 11-12:1 when WOT. Im running bone stock ECU, bone stock MAF, and I was wondering what could cause that, O2 sensor? Temp sensor? :shrug: Any help apreciated

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Re: Lean AFR when cold

Postby yyonline » Wed Apr 08, 2015 11:37 pm

First thing that pops into my head is cold start injector.
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Re: Lean AFR when cold

Postby loudstealthGT-Four » Thu Apr 09, 2015 12:14 am

Whats the AFR at WOT when cold, wouldn't worry too much about the AFR when cruising.
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Re: Lean AFR when cold

Postby warracer » Thu Apr 09, 2015 12:47 am

loudstealthGT-Four wrote:Whats the AFR at WOT when cold, wouldn't worry too much about the AFR when cruising.


It starves for sure, if I WOT when cold (which I never do) aprox 16-17:1 but I never builded up boost , I don't want to blow it up haha
____________
ST185H A-Spec:
-IHI VF28 -BC Racing coilover
-Yonaka FMIC -Swift Spring
-ARP head stud -St205 rear end
-Cometic Metal HG -Supra TT Fuel Pump
-3'' SS straight pipe -Poly bushing
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Re: Lean AFR when cold

Postby MWP » Thu Apr 09, 2015 10:59 am

I wouldn't worry about it.
An AFR that lean won't hurt the engine at all at cruise, or even light acceleration.
It'll feel a bit powerless, but thats all.
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Re: Lean AFR when cold

Postby warracer » Wed Apr 15, 2015 5:26 pm

MWP wrote:I wouldn't worry about it.
An AFR that lean won't hurt the engine at all at cruise, or even light acceleration.
It'll feel a bit powerless, but thats all.


Oh ok good, I was getting worried about knock maybe, but the CEL never came on and the car works perfectly fine after it reached temp.
____________
ST185H A-Spec:
-IHI VF28 -BC Racing coilover
-Yonaka FMIC -Swift Spring
-ARP head stud -St205 rear end
-Cometic Metal HG -Supra TT Fuel Pump
-3'' SS straight pipe -Poly bushing
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Re: Lean AFR when cold

Postby Empiremen » Tue Jan 12, 2016 4:09 pm

Hi, I have the same symptom, have you found what cause the afr to be lean on cold start?
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Re: Lean AFR when cold

Postby klue » Wed Jan 13, 2016 1:18 am

lean afr when cold could simply due to poor fuel atomization. dont worry about it, just avoid heavy load.
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