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2008 BMW 535xi
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Discussion Starter · #1 ·
Hello everyone,
I am wondering if the crankshaft sensor relate to my engine misfire on cyl number 4. Engine code p0304 on Innova scanner and on Carly scanner 0029D0 (misfiring cyl 4)
I have BMW 2008 535XI with 213,000 km. Recently I had a code 002A94 and 003100. The engine was running fine as far as idling goes and there was no misfiring. I replaced crankshaft sensor myself but not the o-ring because it didn’t come with one and since there is no oil leak so I decided to use the same one. After replaced the crankshaft position sensor, the car ran fine . I drove for few blocks without any issue. Car ran perfectly! I was happy and called it done with issue resolved.

The following morning, the engine ran rough upon startup with misfiring in cylinder #4. I pulled the spark plug and it was wet with fuel. I cleaned with brake cleaner and swapped the spark plug from cyl# 3 to cyl 4. Clear the code and re-Started the engine. Code came back with still cyl #4 is misfiring . I swapped the ignition coil too between cyl# 3 and cyl# 4 as well. So now I have spark plug and coil from cyl# 3 and cyl # 4. Still cyl # 4 is misfiring ! I am scratching my head on this one.

Could cranfshaft position sensor installed could cause one specific cyl 4 misfiring ? It is not the spark plug and not the ignition coil because I already swapped the the problem is not following .

Any help on this would greatly appreciated.
Thank you
 

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Under the lift arms
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13,166 Posts
yep...

cam and crank and knock are what i call primary inputs... everything else is secondary

even mis fire codes are just related signals not primary inputs

your having a timing issue... thats being detected as cylinder 4 misfire..

keep on mind that a cam and crank position error can flip flop and report the other depend on what side of the sine wave *if you where looking at it with a scope
 
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BMW CCA 69606
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A bad crank sensor wouldn't cause misfires on only (1) cylinder. Is cyl 4 still wet w/fuel? Leaking fuel injector seems more likely and N54 injectors are problematic. What is the index number on your injectors?
 

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Under the lift arms
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there are two sides to this theory...

yes injector failing or failed will cause a solid misfire but the injector is a device that gets a signal... not gives a single

thats the two sides of the story (*i would not chase a secondary before a primary)

there is also a code block for injectors po250's ish if i remember

a bad crank sensor is a simple term : the wave fourm that is generated by the crank sensor is def capable of making single and random misfires
 
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I'm under the impression that the misfire isn't triggered by a lack of a signal to the coil, but to other parameters (way more complicated of course, since this is a BMW). So a bad plug or bad injector or bad valve (etc.) can cause a misfire code. I'm betting that a leaky injector won't throw a code (it would be a neat trick, but that would require monitoring the actual fuel moving through each injector, which sound too complicated even for BMW). ;-)

I kind of ruled out the crank sensor based on prior experience with them (which was kind of a "running fine, or running like dog poo or not at all" kind of device), but, BMW probably does it different.
 

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Under the lift arms
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Its not more complicated because its a bmw... its basic obd2 *it was standardized in 1996

bad plug
bad coil *kinda the same category (all being fuel injection election timing)

bad valve.... different chapter

your correct.... a leaky injector will just waste fuel and smell bad and possibly blow you up *again no big deal


Its always crank or cam... the timing signal can be viewed in live... but unless you know what it looks like normally..

it messed up would look normal


the problem is electronic timing here....

I put that shit on everything
 

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2008 BMW 535xi
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Discussion Starter · #9 ·
A bad crank sensor wouldn't cause misfires on only (1) cylinder. Is cyl 4 still wet w/fuel? Leaking fuel injector seems more likely and N54 injectors are problematic. What is the index number on your injectors?
Thanks for the responses.
Sound like everyone think I have new problem that is leaking injector. Can that be repaired or only replace it? The plug is wet with fuel when I removed it (from #4)

So I m still thinking about crankshaft sensor not installed properly. I m about to put my old crankshaft sensor back on the car since I did not have misfiring . All cylinder was running. It was running a bit erratic and low power (engine run at reduced power) with old CS.

I just want to rule out injector. If you think that is waste of time and I should go straight to injector.

I need to add one more thing. When engine run warmer. There was no misfiring in cyl 4. Only on cold start.

So:
Do I bother try old CS ?
Do I take new CS and reinstall it with new o ring?
Remove injector number 4 and swap with 3?
Thanks for your time ,
 

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The cheapest approach IS to swap a couple injectors, and see if the misfire follows the suspect injector or not. I wouldn't put the old CS back in, personally... sounds like it fixed another problem, and as others have guessed, it's probably not the source of your single cylinder misfire.
 

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Discussion Starter · #11 ·
I did a bit of research about leaking injector. A simple check is to remove spark plug to see if it wet with fuel. If it is, that is leaking injector . I guess cleaning is not possible. Replacement is the only option.

Questions:
-is it wise to swap the injector to see if the misfiring follow?
- Should I try to clean the injector tip with carb cleaner?
 

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The cheapest approach IS to swap a couple injectors, and see if the misfire follows the suspect injector or not. I wouldn't put the old CS back in, personally... sounds like it fixed another problem, and as others have guessed, it's probably not the source of your single cylinder misfire.
Thank you! I will do the injector swap and will report back tomorrow evening
 

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No harm or cost in swapping the crank sensor, I don't think it will fix the problem though. The fact that you don't have misfires warm also points to an injector problem based on my experience.
Not sure if you are aware, but N54 fuel injectors have unique calibration numbers that need to be programmed into the DME. Swapping injectors is a good test but it upsets the DME's fuel calibration. You should return them to their original positions if you're not going to update the DME with the new positions. When my index 9 injectors leaked I had rough cold starts and the DME would disable the cylinder so car was running on 5 cylinders only.....very noticeable. With the injector disabled and after idling for 15 seconds or so, I could shut down and restart and all would be normal until the next cold start. It seems that after running with injector disabled, the air passing thru the cylinder would remove the excess fuel allowing misfire free running on the restart. BMW says all injectors on a given bank need to have the same index number. The currently sold injectors are index 12 I believe, and they're about $225 each. You need to check your index numbers. After my most recent failure I bought (3) index 12 injectors. I do have (2) good index 9 injectors I'll part with. PM me if interested. I hear some horror stories about cost to ship to Canada though. Used injectors can be found on ebay.
 

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No harm or cost in swapping the crank sensor, I don't think it will fix the problem though. The fact that you don't have misfires warm also points to an injector problem based on my experience.
Not sure if you are aware, but N54 fuel injectors have unique calibration numbers that need to be programmed into the DME. Swapping injectors is a good test but it upsets the DME's fuel calibration. You should return them to their original positions if you're not going to update the DME with the new positions. When my index 9 injectors leaked I had rough cold starts and the DME would disable the cylinder so car was running on 5 cylinders only.....very noticeable. With the injector disabled and after idling for 15 seconds or so, I could shut down and restart and all would be normal until the next cold start. It seems that after running with injector disabled, the air passing thru the cylinder would remove the excess fuel allowing misfire free running on the restart. BMW says all injectors on a given bank need to have the same index number. The currently sold injectors are index 12 I believe, and they're about $225 each. You need to check your index numbers. After my most recent failure I bought (3) index 12 injectors. I do have (2) good index 9 injectors I'll part with. PM me if interested. I hear some horror stories about cost to ship to Canada though. Used injectors can be found on ebay.
I pulled 4 spark plug out and it is wet with fuel . You are all right that injector is leaking . I can’t tell what index number is . Is it 10? I don’t have anything that I can program injector change unless Carly app allows me to do that .
Here is the picture of my injector .
Ps . I am not pulling CS back out . Look like it is not the issue anyway

1031523
 

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Thanks .
i just pulled the injector 4 out to check the injector and want to see how easy to pull it out. It came out fairly easy without extractor tool. The fuel line that feed injector 4 has enough residual fuel pressure even I haven’t start the car for two days. I know this won’t do much but I do have a bit of carb cleaner to I decided to clean the tip a bit.
So I do have a question.
  • do I have to buy injector with index 8 to match?
  • what if I don’t program the injector , will it damage the car or just fuel economy or performance is the issue ?

thanks everyone for your time,
 

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Yes, 08 means index 8. I would check all of the other injectors index numbers. You should be able to see and photo w/o removing. If the others are not all 8's, then maybe you can buy a replacement and rearrange to make them the same on a given bank. I'm surprised to see index 8 injectors. In the US, BMW had a recall campaign to install index 9 injectors. 581 & 227 below the bar code in the second photo are the calibration values that need to be entered into the DME. There is only one pre-cat O2 sensor for each bank, so it's important that each injector supply the exact same amount of fuel for a given opening duration. The codes allow this to happen.
 

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Perhaps finding an 8 on eBay makes sense. Always a gamble, but it isn't real hard to replace if you have to later.
 
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