Car runs lean on highway

[91TSI505]

I can't get my car to stop running lean on the highway,it usually happens when i'm around 65-70mph,slowly creeps to lean,is this normal?Also when i start to boost my car will run lean(Not completley,just starts to creep to the lean area) no matter how much i richen up the AFC,Any suggestions?I am replacing the O2 sensor soon,could it be a boost leak?Thanks in advance

 

[j_woody]

i think it has to do with the mad downforce that wing is creating. the rear end squats from the tremendous downforce making more air go under the car and into you intake, making you run lean.




sorry, um, how do you know it is running lean? i hope it is not a air/fuel guage. if it is i would not worry that much, my understanding is that those are about as accurate as your stock boost guage.

 

[Defiant]

Constant-speed, steady-state cruising? You should be lean. You're making about 30 horsepower to cruise. What matters is that you go richer when accelerating.

 

[DSMJim]

Originally posted by 91TSI505
I can't get my car to stop running lean on the highway,it usually happens when i'm around 65-70mph,slowly creeps to lean,is this normal?Also when i start to boost my car will run lean(Not completley,just starts to creep to the lean area) no matter how much i richen up the AFC,Any suggestions?I am replacing the O2 sensor soon,could it be a boost leak?Thanks in advance

How do you know that your running lean? Please please please tell me your not looking at one of those stupid Autometer A/F gauges. If you are please goto your car, pull out that gauge and throw it in the garbage and start driving your car normally again. That is the most useless piece of crap gauge ever.

I absolutly refuse to put those into guys cars because no matter how much I explain how they work they always come back saying "I think my car has a problem, the A/F gauge is bouncing around" blah blah because they have no idea what the gauge is supposed to read.

 

[red91tsiawd]

it has to be the park bench *remember PUPPY CHOW when u say it *

 

[91TSI505]

I'm reading it from the AFC's voltage.

 

[Keaka26]

our cars naturally run leaner during part throttle operation to achieve cleaner emissions as well as better fuel economy... Get a pocketlogger and look at your fuel trims, then you might know if youre actually going lean.

 

[cait sith]

If you're not using a wideband, O2 readings aren't worth crap.

 

[13secGST]

yeh...I wouldn't worry about it...put the AFC settings back where they used to be...do you have an EGT gauge...cause that is pretty acurate at finding out how lean/rich you are...too hot-your lean...to cold-your rich.

 

[Keaka26]

Im going to hafta argue the EGT thing. Too hot generally equals timing pull, which doesnt necessarily equate to being too lean...

 

[steve]

If your crusing (part throttle, steady state) and your O2 aren't cycling, then it's time for a new O2 sensor. I know I'm running closed loop at 65-70 when I'm crusing.

Steve

 

[Defiant]

Originally posted by DSMJim
I absolutly refuse to put those into guys cars because no matter how much I explain how they work they always come back saying "I think my car has a problem, the A/F gauge is bouncing around" blah blah because they have no idea what the gauge is supposed to read.

Waitaminute... those things are supposed to READ something? I thought they were just hi-tech wizzy pod hole plugs. ooooo liiiiights....