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Keep it clean
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8,069 Posts
Discussion Starter #1
Hey All,

I am mostly retired from e46 life, but I have a friend that wanted me to work on his car. 2005 325i with 208k. He bought it as a cash car to get by. I'm just trying to help him get this thing running right for a little while.

He brought it to me with no history on the car. I pulled the codes with ProTool.

Initially I had codes from pre-cat O2 sensors (bank 2), Fuel trim (bank 2), misfires on 1, 2, and 3.

The car was an oily mess. Started with some maintenance.

Vanos seals
Valve cover gasket
New plugs
New Pre-cat O2 sensors
Cleaned MAF, checked filter

Cleared all the codes

I was still getting a consistent Misfire on 2. Car starts and idles fine. You can feel it hesitate when you drive. Under load when you push it, you'll get a code for #2. I swapped his coils around. Same cylinder. I swapped in a set of newer updated N54 coils. Same cylinder.

We proceeded to address more issues and clean up more oil mess. I replaced CCV and hoses, thermostat, water pump, OFH gasket, oil dipstick tube, throttle body gasket. CCV was definitely leaking oil. 2 hoses were cracked.

Still misfire. Same cylinder.

Changed fuel filter for kicks.

Same.

Just pulled coils and plugs and did a compression test. All came out ok. Found that 1-3 plugs were black. 4-6 looked to had a clean burn.

A friend and fellow old Fanatic is suggesting MAF failure. I'm leaning that way as I don't want to start pulling injectors.

Any additional thoughts would be great!
 

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Keep it clean
Joined
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8,069 Posts
Discussion Starter #3
Well, I'm going from an MHD 1+ N54 to a M54B25. Haha.

Yes, I can feel the car hesitate and buck. It goes into limp mode and really I can't push it at all. Have to either kill it and pop the clutch and drive it home, or pull over and restart.

Picking up a MAF this afternoon. Will update.

Does the car feel slower than it should? Does the misfire start if you're pushing the car around 4-5k RPM? If you push the car anyway can you get more cylinders to misfire?
 

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Here to serve y’all
2004 330Ci 85k miles
Joined
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11,093 Posts
You may have a failing fuel pump, clogged cats, a large vacuum leak, or other issues.

Can you gather the following at hot idle and post for review?
- each trouble code in standard OBD Pxxx format with description (lookup on obd-codes.com)
- all four fuel trims (short term and long term for banks 1 and 2)
- MAF value in grams/second units
If you already have the OBD Fusion app, just do a Diagnostic Report and post a link here, that will have all of the above and more.

That will give a base line of how the fuel management is doing and point what to look at next.
 

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Keep it clean
Joined
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8,069 Posts
Discussion Starter #5
Replaced the MAF at his request. Got it out and still got misfires for 1 and 2.

P0302, P0301, and this time I got P1625. That may be because of the compression test.
 

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10,036 Posts
Something tells me that the problem is related to bank 1. Why? The plugs from bank 1, from your description, were a bit fouled while those from bank 2 are clean. Fouled plugs typically mean the engine is either burning oil or the mixture is too rich. I’m betting on the latter.

What brand are the new pre-cat oxygen sensors? Bosch is the only brand to buy.

Get the OBDFusion app for your smartphone or tablet. Then search this forum for threads on OBDFusion in which jfoj has commented. His posts will tell you:
- which communications adapter to buy
- how to set up the app
- how to use the app to see different data streams
- how to record and export the data.

Now, pull the plastic cover and check the ground strap for the bank 1 coils. Also, check the connector where the bank 1 pre-cat oxygen sensor connects to the engine harness. Make sure the connection is clean and tight.

What brand of MAF did you install. The only brand of MAF to install is Siemens/VDO. However, the MAF is likely ok as the problem appears to be bank 1. If the MAF was bad it’d affect both banks.
 
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