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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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Old 07-04-2016, 01:49 PM
simonus simonus is offline
Location: USA
Join Date: Jul 2016
Posts: 4
Mein Auto: BMW 325i 2003
Notorious misfires

I've read tons of threads about misfires in E46 and did not find a solution for mine.
So I would like to share the data that I have collected using the code reader.

Brief description of the situation in which the issues occurs

Within the first 3 minutes on the cold engine start code P0303 (Cylinder #3 misfire) is posted as pending fault code. It happens on low RPM (650-750) and the engine temp below 100F.

Two mechanics (BMW "experts") tried to find the fault and could not but tried to
convince me to replace all ignition coils and spark plugs, which was already done and
do a few other things. The last BMW expert who touched my ignition coils did not
connect the ignition coil connector on cylinder #6 and it was misfiring ever after
his diagnostics work, which I found out only after I bought the code reader
and fixed the problem myself.

Can Bimmerfesters brainstorm this problem?

One day I thought let me ask Bimmerfesters put their brilliant minds together and
identify the culprit. In this post I submit "hard evidence" of the fault.

The evidence that I can provide comes from a very useful feature in the code reader.
It is called Freeze Frame that provides a snapshot of most system components status at
the time when the fault code was registered. I have made 3 pictures of each Freeze Frame

I have attached 3 small pictures. I'd prefer to insert them but did not have
the URL ready for exposure. I look forward for ideas and conclusions.

Attached Thumbnails
Click image for larger version

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Name:	FreezeFrameData2.jpg
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ID:	569420   Click image for larger version

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ID:	569421  
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Old 07-04-2016, 02:31 PM
Fast Bob's Avatar
Fast Bob Fast Bob is offline
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Location: Here, there, everywhere....
Join Date: Jun 2004
Posts: 38,800
Mein Auto: 2004 330Ci ZHP 3 pedals
Usually, the first approach would be to try the "Process Of Elimination" method, i.e., swap that no. 3 coil with one from a different cylinder, and see if the fault code follows the coil.
The road goes ever onward....
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When faced with choosing between two evils, always go with the one you`ve never tried before....
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Old 07-04-2016, 07:04 PM
simonus simonus is offline
Location: USA
Join Date: Jul 2016
Posts: 4
Mein Auto: BMW 325i 2003
Additional Details

Fast Bob, Your suggestion is great and it was done by my mechanic 3 years ago
at the time when i bought the car and he made some upgrades. He swapped the
ignition coil and spark plug from cylinder #2 to #3 but the fault code kept coming
on cylinder #3. Then last year I replaced all coils and spark plugs using OEM parts.

I hope that some parameters in the Freeze frame data shown in my pictures
can help or give some clue where the problem is. For example, "Calculated Load 37%"
is it a fuel load? If yes, then it may point to fuel injector. Or why misfire happens only on one cylinder #3 and only on cold engine start. Other then this limited misfire, the car runs fine
with good power and has no other fault codes.
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Old 07-05-2016, 06:57 AM
marcozandrini marcozandrini is offline
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Posts: 2,346
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That number is the calculated load being placed on the engine.

The next step is to have compression tests performed on the engine. You could have a bad compression ring or a valve that's not seating properly. Also, a fuel pressure check is in order, just to be sure. You may have a finicky injector.

Btw, what's the maintenance history of the car? What brand and octane of gas are you putting in the tank? How is the car being driven? Are you taking primarily short trips?
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Old 07-05-2016, 09:51 AM
lincolnshibuya lincolnshibuya is offline
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Location: KC MO
Join Date: May 2016
Posts: 106
Mein Auto: bmw 325xi
misfires could be a lot of things
- spark plug, ignition coils - you seem to have done this by swapping/replacing
- injector leak/clogged - you could also try swapping
- intake/exhaust valve leak - you could do a compression test or a leak down test to verify

if you leave the misfires for too long it could damage your catalytic converters.

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Old 07-05-2016, 05:32 PM
simonus simonus is offline
Location: USA
Join Date: Jul 2016
Posts: 4
Mein Auto: BMW 325i 2003
Thanks for response

Thanks for everything.

I'll try to answer some questions and ask mine.

I use the car once or twice per week for short trips.
I tried BMW dealership and several mechanics BMW "experts" but nobody
promised to find the source of the problem to say nothing about fixing it.
I wish I could fix it myself, but I am not a mechanic at all.

But what upsets me most is that I am sure that BMW is a great car and
why I should spend $10K to fix a misfire issue. If I take my car to a mechanic
they do the same thing as the doctors - they think about how to charge and not
how to fix.

Thanks for any advice
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Old 07-05-2016, 05:37 PM
SloppyTopM3 SloppyTopM3 is offline
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Location: Quincy Illinois
Join Date: Jul 2016
Posts: 7
Mein Auto: 1995 BMW M3
Have you tried testing for air leaks? Take a hose or large water bottle and trickle water around the injectors and the intake gaskets. If you hear a sucking or a change in the engine, you have your culprit. Also I would look under the intake and make sure all the vac hoses are in good shape.
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Old 07-05-2016, 06:12 PM
marcozandrini marcozandrini is offline
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Join Date: Feb 2014
Posts: 2,346
Mein Auto:
Notorious misfires

Ok, let's try this: take you car on a weekly basis for a 15 mile high speed run. This will clear out the cobwebs.

These cars are designed to run at serious triple digit speeds on the autobahn. They do not like short trips.

Last edited by marcozandrini; 07-06-2016 at 07:05 AM.
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Old 10-15-2016, 02:19 AM
acoste's Avatar
acoste acoste is offline
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Location: California
Join Date: Nov 2011
Posts: 2,309
Mein Auto: 2010 550i MT
Have you got this solved?
2003 BMW 325i @190k and counting
1998 BMW 528i MT @ 231k //sold
1997 Saab 9000 //sold
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