Ever since about a week ago after i went cruising with some friends, my car has been running lean as soon as i start to move/drive the car. Car idles and revs fine.

Afr's are good at idle, 14.7-15, but as soon as i start moving/driving afr's act as if they are dropping but then shoot up to 15.5-16.5 while im not in boost. Only done it once but went in boost to see what the afr's would do and they acted like they were dropping, going as low at 12.5-13, but then rose and stayed at 14.7, once i saw that i let off the throttle.

Setup:

Stock ka, compression test came up 180 on all 4, test was done a couple days ago
arp head studs
felpro headgasket
s14 t28 8psi
370cc inj
isis fpr
walbro 255
Nistune(only adjusted some stuff, k constant maf timing etc, no tune yet)

Only parts that i can think of that could cause this problem are my fuel pump or fpr. Both have less that 1k on them. Other than that, vacuum leak maybe.

Full details on what has happened is here:
www.ka-t.org :: View topic - Help.. afr's lean after a cruise

Any help is appreciated.

 

Could just be an exhaust leak, before your a.f.r. o2 sensor. Every time my 2 previous manifolds would crack, my numbers would jump all over the place. What kind/type of manifold do you have, have you ran across anything that would jolt the car fairly drastically? Where is your a.f.r. o2 sensor located? Chech your gaskets as well.

 

isis v2 mani

Only leak i have is in between the downpipe and test pipe. Will be fixing soon but that isnt causing this problem.

Wideband o2 is 1-1.5ft back from the turbo.

 

12.5 in boost is pretty damn lean especially for a ka. I always had my cars drop to 11.0-11.5 under load. A de-accel lean condition is normal though. If your foot is planted and you are pulling high 12's for afr something is definitely wrong. Try re-calibrating your sensor. If that doesn't work bring it in to a dyno and do a few baseline pulls to get an idea of what the car is doing.

 

doesnt wideband have to be 3 feet from turbo?
i read 36 inches

correct me if im mistaking

 

No, it really doesn't make much of a difference.

 

^+1 location dosent really make a difference. How old is the o2 sensor itself? if it has alot of time on it or time spent under extremely rich conditions, it could be going bad. Low to mid 12's are pefectly safe under lower boost levels <25psi. You will normally make the most power when the afr's are in the low 12's.(under boost conditions) 15's while crusing are ideal for maximum mpg. While not under boost conditions, it is nearly impossible to hurt your motor. It will break if things aren't right under bost conditions.