Car runs rich, shows lean

[SkURTnDSM92T]

My car has been running pretty rich for awhile. I hooked up the AFPR and have been working on tuning to try and fix this. However, even at idle when rich, my AFR guage reads LEAN....does this mean I have a bad O2 sensor?

 

[fwdturbobov1996]

Your afr gauge, do you mean that sorry excuse for a guage that is the blinky rainbow, that thing is junk.

 

[donmagicjuan]

When you say your car has been running pretty rich for a while, what are you basing this on?

 

[FORMONTOYA]

If the car is truly running rich and a log is showing lean...then it's either a bad O2 or an exhaust leak pre O2 sensor.

But yes, the "blinky" light narrow band O2 gauge is junk. And as stated, what are you basing the rich condition on?

 

[SkURTnDSM92T]

Well I was running a 255 without an AFPR for awhile, before I know it was a bad idea.. That and the fact that I have soot in my exhaust and what not..

Also, when my car was warming up the other day, i put my hand in front of the exhaust and I am pretty sure got little specs of what I think was fuel on my hand. This only happened after the car had been sitting all night..

 

[SkURTnDSM92T]

If the car is truly running rich and a log is showing lean...then it's either a bad O2 or an exhaust leak pre O2 sensor.

But yes, the "blinky" light narrow band O2 gauge is junk. And as stated, what are you basing the rich condition on?

I dont have a logger. Im basing it on the fact that I can smell gas often..read above as well

Why is the AFR guage junk?

 

[andymoraitis]

A/F gauges are crap because they don't show a true air/fuel ratio. Only a wideband will do that reliably. If you're still running without the AFPR of course you'll be rich. Add the absence of a cat and you'll get all kinds of black crap in the tailpipe and on the floor. You should see the spot I have in my garage.

The only thing an A/F gauge is good for is to ensure that the O2 is cycling. Other than that they're worthless light shows.

Finally, the stuff spattering on your hand was condensation coming out of the exhaust as the cool air inside it was displaced by hot exhaust. It only happens on warmup and it's normal.

 

[FORMONTOYA]

I dont have a logger. Im basing it on the fact that I can smell gas often..read above as well

Why is the AFR guage junk?

A narrow band O2 sensor has poor resolution, 0-1v, which just about anything out of 14.7:1 is pointless. A wide band O2 sensor has better resolution, 0-5v, which is normally from 10:1-20:1.

I did read what you had and was trying to relate that basing your information off a NB O2 gauge is pointless. Get a logger if you what better feedback from the car.


edit: beaten by Andy

 

[SkURTnDSM92T]

I know that narrowband is not a supreme tuning tool..but for now it is what I have.

My question was, if my O2 sensor was bad, how would i know?

 

[FORMONTOYA]

When they start taking a dump they will start to read lean....to the point that they will eventually read 0. Of course if you have an exhaust leak pre O2, it will make the readings show lean also. To check that, run some Seafoam through it. If it has leaks you'll see it.

 

[andytalon]

What I do when my car starts running bad is just this. (in this order)
-Turn the car off
-Unhook battery teminal (black) Negitive
-Take Biss screw, screw it all the way down till it stops then do 2 turns out and leave it alone!
-Next wait 20mins so my ecu can reset
-Rehook battery
-Turn car on
-Set Fuel pressure
-Set base timing to 5 degrees btdc (its the notch in between the T and the 10 marks.)
-Then let the car idle for about 15 mins and allow the ecu to find itself.


Next thing I would do is just basic matenance

Is the car bogging down at all, hows the idle is it at 750????

Some key points if not already known.
-1g base fuel pressure-37psi (with vac line off)



(Sorry about spelling )

 

[SkURTnDSM92T]

the car does not like to idle that low AT all..when you say set base timing 5 deg BTDC, I have never done ignition timing. I am getting a friends timing light and doing it tomorrow.

Ill try this and let you guys know whats up

 

[chuckg]

Is your fuel pressure properly adjusted?

 

[Auto RS T]

I was thinking this problem may have to do with running 660's on an afc only for tuning. What are your settings? Possibly you are seeing so little airflow that the computer is injecting little fuel to match the little airflow. Sounds like you need a different tuning device or a keydiver chip. Does this make sense to anyone else, or am I completely off here?

 

[AWD monster]

Another way to tell if your o2 sensor is bad:

AFC - Do the blue wire mod as found on vfaq.com. Then goto the sensor check section of your afc, i believe the o2 voltage should read:

In2: 0.90

I believe that should be when your on the throttle too. Anyone back me up on the correct voltage?