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Old 02-13-2020, 12:29 AM   #1
moyikai
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325i Misfires No Codes

2003 325i. I have a misfire that I can't track down. No engine codes, no issues with the diagnostics. I had a P0174 lean code, but I tracked that down and fixed the evap leak. Now no engine codes but I definitely have a misfire. It got so bad that eventually it tripped a P1374 code (misfire in cylinder 3). Swapped out coil, spark plugs, and tested each cylinder by disconnecting the coils one by one (all behaved the same), then cleared the codes. No new codes yet, but it is still misfiring really noticeable at low RPM (<2500) under power. Nothing seems to have worked. Here is a summary of what I have replaced trying to find the problem;

Spark plugs
Valve Cover Gasket
EVERY vacuum line in the car
Entire CCV system & hoses
MAF sensor
Fuel Filter
Upper & lower intake boots
Oil filter housing gasket
Gas Cap
DISA Valve
Cleaned the ICV

STFT and LTFT are well within norms.
MAF is good.
Timing is within norms

I even started to doubt a misfire and thought the clutch might be slipping, so I replaced the clutch (it needed to be done anyway).

When I bought the car 18 months ago I did a full cooling system refresh (water pump, expansion tank, hoses, clamps, etc.)

I did an oil change recently and used STP Synthetic, not the recommended Castrol (weight and viscosity was correct). I have always used Castrol but I can't imagine that would cause misfires like this, but the issue seems to have started (or at least seemed more noticeable) around the same time. My wife thought I screwed up the oil change.

Even though I've done all the work myself, I've put almost half what I paid for the car in new parts on it. I'm at my wits end. Any help??!
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Old 02-13-2020, 09:01 AM   #2
bonestockE36
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Compression and leakdown test.
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Old 02-13-2020, 09:37 AM   #3
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You make no mention of your current mileage.
Your misfire could be a myriad of things from oil entry to the combustion chamber to one injector intermittently going bad and/or not delivering the correct amount of fuel.

Chasing intermittent misfires (not long enough of an event to capture/set a fault) can be very frustrating for technicians.
When faced with such and a myriad of parts used we have to resort to going cowboy on it.
Looking at live data over on the Mode $06 side, watching misfire counts live and try to make a correlation to another part causing the issue, even breaking out a Picoscope to try a capture. Watching crankshaft acceleration rates/adaptation numbers for the firing (not the general adaptations) can point one in the right direction as to what cylinder is misbehaving.

Might I suggest you swap out the injector with cylinder # 3 & 2. (if the misfire is truly on cyl. #3 currently? Verify FIRST) Otherwise you'll chase your tail.
If the misfire moves, try in the tank fuel cleaners such as L-M 2030 Pro Line fuel system cleaner.

Report your findings to help others in the future please.
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Old 02-13-2020, 10:42 AM   #4
PabloCruise
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Quote:
Originally Posted by moyikai View Post

My wife thought I screwed up the oil change.
Ha ha, thanks Baby!



Also curious as to how many miles are on this crate.

Have the 02 sensors been replaced lately?
Crank position sensor?
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Old 02-13-2020, 11:41 AM   #5
moyikai
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I just hit 80k miles on the car. I bought the car at 67k about 18 months ago. I don't know if the O2 sensors have ever been replaced, but they look relatively new.

I haven't swapped out injectors yet, I will try that today to see what happens. I ran fuel system cleaner 2 tanks ago.

I have not replaced the cam position sensor either.

My wife is fed up with spending money chasing this misfire, and just wants to take it to a shop, but I feel like they will have gone through my same process to find the misfire, and charge me $120/hr everytime they pop the hood. I'm not trashing them, they gotta make a living, but if I can find it myself I thought I could save some money. Should I just pay a pro, or am I on the fight track?
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Old 02-13-2020, 11:46 AM   #6
moyikai
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Quote:
Originally Posted by bonestockE36 View Post
Compression and leakdown test.
I haven't done a compression test yet, but it's on my list. I don't have a tester, so I'm trying to rule out stuff I can check first before I go out and buy more new stuff. Thanks for the suggestion. I will keep this thread updatwd with my findings.
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Old 02-13-2020, 12:00 PM   #7
moyikai
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I watched a 50skid video on chasing misfires and it was reall helpful (link below). I am trying to follow his same process, altough my symptoms are a little different.



My misfires are at startup and idle, and persist even after the engine is warm. They keep occurring through the entire RPM range, but are most noticeable while accelerating from the lower range of the torque curve. It happens less often if I accelerate slowly. Yesterday it got so bad I could barely maintain 60 mph on the highway, and it finally tripped the engine light (P1347 - misfire cylinder 3 at fuel cutoff). I swapped coil 3 with cylinder 2, and cleared the codes. It still misfires, but it hasn't tripped another code yet to tell if the problem traveled.
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Old 02-13-2020, 01:36 PM   #8
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Quote:
Originally Posted by moyikai View Post
I just hit 80k miles on the car. I bought the car at 67k about 18 months ago. I don't know if the O2 sensors have ever been replaced, but they look relatively new.

I haven't swapped out injectors yet, I will try that today to see what happens. I ran fuel system cleaner 2 tanks ago.

I have not replaced the cam position sensor either.

My wife is fed up with spending money chasing this misfire, and just wants to take it to a shop, but I feel like they will have gone through my same process to find the misfire, and charge me $120/hr everytime they pop the hood. I'm not trashing them, they gotta make a living, but if I can find it myself I thought I could save some money. Should I just pay a pro, or am I on the fight track?
80k miles on an '03? That is low miles. Sometimes lack of use can create issues if the vehicle sits for long stretches.

I am no expert, but I do think o2 sensors become less effective from miles and from age.

I do not know how these things behave when the crank position sensor fails, but I imagine it can be problematic.

My wife gets fed up whenever our e46 hiccups, but she just wants to sell it and buy another Land Cruiser.
I love that woman...
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Old 02-13-2020, 02:15 PM   #9
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If the car has a 5 wire MAF, a DME flash will most likely be required.

On manual transmission cars the DME Ignition Timing Map problem is far more obvious than on automatic transmission cars.

https://forum.e46fanatics.com/showthread.php?t=966614

https://forum.e46fanatics.com/showthread.php?t=1121703

This problem has plauged about 10 years of different BMW models in some form or another, it is not just a problem with the E46 and the I6 engines.
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Old 02-13-2020, 02:29 PM   #10
moyikai
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UPDATE:: I was finally able to pinpoint the coil on cylinder 3 was bad. Here is what I did:

I put all coils back in original positions, and started over. Cold start this morning (I live in Hawaii, so cold is a relative term). It was misfiring right from the start. I did an engine balance test disconnecting each coil one by one, but they all behaved the same. I felt like I needed to push the engine to get it to trip a code, but I have been afraid to drive hard because I didn't want to cause more damage, and I'm still breaking in my new clutch. So I drove about 10 miles doing low RPM pulls in 3rd and 4th gear. It misfired pretty badly and tripped the code P1347 (misfire cylinder 3 fuel cutoff).

I pulled back in to my driveway and without turning it off, I did another engine balance test and found cylinder 3 coil was definitely not contributing. I swapped cylinder 3 coil with cylinder 1 coil and did the same test. Engine code moved to P1345 (misfire cylinder 1 fuel cutoff). So the misfire travelled with the coil.

I bought a new coil and replaced it. Went for a test drive doing the same type of low RPM pulls to force the code, but it is running silky smooth. No misifres, no codes. The coil I bought was an aftermarket OEM replacement made by Import Direct (part #23-0546) from O' Reilly $65.00). I don't know how well an aftermarket part will hold up, but I will report any issues. I will say right from the start that it doesn't seat quite as snug and tight on the spark plug, and the connector isn't as snug either, but it's working for right now.

What I learned:

1. You have to be patient and meticulous trying to find these random misfires. Log and record everything, and use the scientific method to narrow down the source of the problem.

2. I had to bite the bullet and push the engine beyond what I was orginally comfortable with to force the codes to pop. I'm NOT a professional, so I can't say this is a good method, but without stress testing it to force consistent symptoms, I couldn't locate the issue. A pro with more experience and better equipment might have a more refined method.

3. These cars ARE worth the headache. When I finally got it running good and felt the silky smooth torque (even from the 2.5L), it reignited my love for the e46.

Thanks to everyone for your help and suggestions! I post my experience with the aftermarket coil.
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Old 02-13-2020, 03:47 PM   #11
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I always like to hear the resolution - thanks!
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Old 02-13-2020, 04:47 PM   #12
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Quote:
Originally Posted by moyikai View Post
The coil I bought was an aftermarket OEM replacement made by Import Direct (part #23-0546) from O' Reilly $65.00). I don't know how well an aftermarket part will hold up, but I will report any issues.
Thatís a bit pricey for an aftermarket coil. Which brand is it?

You can get an OE coil for around $25.
https://www.fcpeuro.com/BMW-parts/32...5&b=5&d=589&v=
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Old 02-13-2020, 05:10 PM   #13
moyikai
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That's a bit pricey for an aftermarket coil. Which brand is it?

You can get an OE coil for around $25.
https://www.fcpeuro.com/BMW-parts/32...5&b=5&d=589&v=[/QUOTE]

The brand I bought is "Import Direct". If I have more trouble with them, I'll try the fcpeuro one. Thanks!!
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