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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 08-03-2005, 09:56 PM   #1
Guy With A BMW
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Running LEAN maybe....how to fix/run richer?

Anyone know how to tell if you are running lean, cause I think I am. Car doesn't pull that much in high gear!

How do you correct it and run rich/richer?
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Old 08-04-2005, 03:12 AM   #2
rooneym
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Quote:
Originally Posted by Guy With A BMW
Anyone know how to tell if you are running lean, cause I think I am. Car doesn't pull that much in high gear!

How do you correct it and run rich/richer?
Hmmm, i do not think there is a way to adjust the A/F mixture yourself. I'd imagine that you have have to get some software work done. Is it possible your MAF sensor is not working properly, or maybe you have an intake leak.

-Mike
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Old 08-04-2005, 03:58 PM   #3
Guy With A BMW
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Quote:
Originally Posted by rooneym
Hmmm, i do not think there is a way to adjust the A/F mixture yourself. I'd imagine that you have have to get some software work done. Is it possible your MAF sensor is not working properly, or maybe you have an intake leak.

-Mike
It would make sense if the MAF sensor is not working properly cause running lean means more air than fuel....but if MAF is bad would it not put fault code and trip Engine light?
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Old 08-04-2005, 11:08 PM   #4
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Quote:
Originally Posted by Guy With A BMW
Anyone know how to tell if you are running lean, cause I think I am. Car doesn't pull that much in high gear!

How do you correct it and run rich/richer?
What does not pulling in higher gears have to do with running lean? That's more likely if you are running rich.
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Old 08-05-2005, 01:52 AM   #5
ADA
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FREE BUMP.

There are a few people on this board that will be able to help you. There, I am offering a free bump. =)

P.S I heard that your pre-cat o2 sensors are responsible for the fuel trim/mixture of your car.
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Old 08-05-2005, 11:14 AM   #6
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Quote:
Originally Posted by ADA
P.S I heard that your pre-cat o2 sensors are responsible for the fuel trim/mixture of your car.
Correct, the car uses readings from pre and post cat to tune the A/F ratio in order to meet emissions requirements.

If the car is not pulling its probably a sparkplug or gunked up injector, clogged fuel filter, dirty air filter.. could be a number of things causing that.
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Old 08-05-2005, 12:23 PM   #7
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I am using Apexi AFC-Select to tune my A/F ratio. I am happy with the result. If you only have intake, cat and exhaust. It will help you.


The Super AFC (Air Flow Converter) Select is based off of the world renowned S-AFC II piggyback subcomputer. The S-AFC Select is designed to fine tune and "squeeze" power out of existing engine setups by allowing the user to modify the fuel curve with precision accuracy. Since the act of simply bolting on performance products does not make maximum horsepower, the S-AFC Select allows the user to calibrate the fuel system in accordance with performance upgrades as they are installed. The AFC modifies the air flow meter/ pressure sensor signal voltage going to the factory ECU (Engine Control Unit) to change the amount of fuel injected. The S-AFC Select utilizes a VFD (Vacuum Florescent Display) to display critical data in three different modes.

Features for the S-AFC Select include: Newly designed case and user interface, single button menu navigation, 12 point fuel correction in 200 RPM increments, data storage for two different correction maps, password protection, integrated knock monitor, and 4 different display options.

The Deceleration Air Flow Correction cures erratic idle problems for Hot Wire vehicles equipped with an open atmosphere blow off valve. The S-AFC II can also display an incredible amount of data including: Air Flow Capacity (Hotwire and Flap Type only), Engine RPM, Throttle Position, Pressure Sensor voltage, Karmann Frequency, and Air Flow Meter Correction.

The S-AFC Select displays data in three different modes: Numerical, Analog, and Graph. Numerical Mode allows the user to monitor up to four different parameters in numbers and also shows peak hold values on demand. The Analog Mode displays up to two values in an easy to read meter style display. Peak Hold is also included in this function. The Graph mode offers real time graph plotting with a Ghost map trace feature built in. The graph can replay movement up to 60 seconds.

CONCEPT: All the functions of the world famous S-AFC II with built in calibration for use with European cars.

CHARACTERISTICS: Piggyback fuel controller with integrated knock monitor. 12 point fuel correction in 200 RPM increments. Separate HIGH and LOW throttle maps. Data storage for two different maps.
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Old 08-05-2005, 05:26 PM   #8
Guy With A BMW
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Quote:
Originally Posted by Mike Benvo
Correct, the car uses readings from pre and post cat to tune the A/F ratio in order to meet emissions requirements.

If the car is not pulling its probably a sparkplug or gunked up injector, clogged fuel filter, dirty air filter.. could be a number of things causing that.
I've already replaced plugs with Iridium ones, done a 3 step clean that cleans injectors and T-body and just got a new air filter....fuel filter?...hmm...car only has 30k on it, but is 4 years old....so dont know.

But, I read somewhere that if your car does not pull so well at high gear that you are running lean.

Would you not get a light and code dump if you are running lean due to knocking engine?
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Old 08-05-2005, 07:15 PM   #9
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Quote:
Originally Posted by Guy With A BMW
Would you not get a light and code dump if you are running lean due to knocking engine?
Not necessarially. It has to be way out of range to throw a code. OBD II is constantly adapting fuel trims so a code may not be thrown.

The right way to go about diagnosing this problem is to take your car to be dynoed. Then you can see if you are making the power you are supposed to, and if the A/F ratio is on or off target. You can't expect to solve a problem like this unless you take it step by step- diagnosis then solution.
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