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Discussion Starter · #1 ·
I've been trying to source lean codes for awhile now, I've spent plenty of time researching how to analyze fuel trims to see what the problem is. I recently smoke tested the car and could not find any leaks, however I took the intake manifold off, replaced the ccv and all associated gaskets anyway because it was still on the original. On my 2005 there were not a lot of vacuum lines under there unlike the earlier models I have seen, so not a lot of other areas it could leak under there. After putting everything back together the fuel trims were the same (all over the place).

MAF readings were around 3g/s with AC off and 4g/s with AC on at idle. I've been suspecting the MAF because my car has a Dinan air box that uses an oiled filter (maybe that's messed it up?). Before spending $250 I would like to have some confirmation. Car is at about 125k miles and still on the original O2 sensors. Bank 1 has always run 1-2% more lean than bank 2 as you'll see in the data

As seen in the hwy file I did a third gear pull up to about 5.5k and was only able to achieve an 80% calculated load value.

Any opinions?

 

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Oiled air filters do have a tendency to ruin mafs, from my experience they should be running about 5 grams per second at idle. Anything more or less is an indication of a problem. I would look at the disa valves there are 1-2 depending on the motor you have in the vehicle. They get stuck open or closed they also internally break and they don’t move with the plastic gear inside the valve. If you replaced vacuum lines and gaskets and smoke tested it, and found no issues. I would do the disa valves they can produce lean issues or you could have an issue with fuel. Lean is too much air or not enough fuel I would check injectors for carbon build up and fuel pressures too. Good luck and let me know what you find.


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Discussion Starter · #3 ·
Oiled air filters do have a tendency to ruin mafs, from my experience they should be running about 5 grams per second at idle. Anything more or less is an indication of a problem. I would look at the disa valves there are 1-2 depending on the motor you have in the vehicle. They get stuck open or closed they also internally break and they don’t move with the plastic gear inside the valve. If you replaced vacuum lines and gaskets and smoke tested it, and found no issues. I would do the disa valves they can produce lean issues or you could have an issue with fuel. Lean is too much air or not enough fuel I would check injectors for carbon build up and fuel pressures too. Good luck and let me know what you find.


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Thanks for the response, my next step is to test the fuel pressure. I did recently rebuild the disa with the GAS kit and test the diaphragm when I did it to make sure it was still working properly. I also ran the car with the MAF unplugged and the short and long term fuel trims summed closer to zero but I wasn't sure if that was just because the car defaults rich when the MAF is unplugged.
 

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2003 330cic, 2003 325iT
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Take a look at the lean code guide in my signature. Many of the items you bring up are addressed. I would definitely test the fuel pressure, and it is time to change your precat o2 sensors. Once you work those out, then see how the fuel trims are adapting before replacing the MAF
 

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Even clean the mafs before replacing them so you can see if it makes a difference and like ^ said test fuel and even get a sample and see how much ethanol is in it and change pre o2’s


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I was unable to open the CSV files in Excel. I think you need to set up OBDfusion and produce the fuel trim logs exactly as suggested in https://www.e46fanatics.com/attachments/obd-2-instructions-2021-v1-pdf.926892/

Here is the thread it came from:

So, the lean codes existed before you took off intake and replace CCV? Is that correct?

I hope you replaced your cooling pipes while you had the intake off.

Did you check the rubber caps on the side of the intake facing the firewall?

Please describe how you smoke tested...Did you do it? Did you have a compressor? Where did you introduce smoke.
 

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Discussion Starter · #7 ·
I was unable to open the CSV files in Excel. I think you need to set up OBDfusion and produce the fuel trim logs exactly as suggested in https://www.e46fanatics.com/attachments/obd-2-instructions-2021-v1-pdf.926892/

Here is the thread it came from:

So, the lean codes existed before you took off intake and replace CCV? Is that correct?

I hope you replaced your cooling pipes while you had the intake off.

Did you check the rubber caps on the side of the intake facing the firewall?

Please describe how you smoke tested...Did you do it? Did you have a compressor? Where did you introduce smoke.
Yes that's correct and it only trips the cel on longer drives, I made a smoke machine with a jar, soldering iron, and a bike pump. It goes into the intake boot, and had enough pressure to almost pop the glove I use to put over the intake boot.

I don't have an android currently so I used my laptop to log the data, I also provided the excel files with all of the data sorted from the CSVs in that dropbox. The rubber caps were still intact, I had to replace one of them a couple years ago that I found with the smoke test.
 

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The Excel files I opened had a lot less data than the CSV files.

Do you have an Iphone? OBDFusion works on an iphone just fine.
 
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