Misfiring at 5,500 rpm or higher with little to no engine load - Page 2 - BMW M5 Forum and M6 Forums
E39 M5 and E52 Z8 Discussion 1998-2003 Advertiser's Forum

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post #11 of 47 Old 29th March 2019, 03:12 PM Thread Starter
SupercarFreak
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Thanks for all of the great recommendations guys.


Just ordered 4 02 sensors, 2 MAFs, fuel filter and 1 bottle of fuel system cleaner. We'll start there.



Fuel tank levels in the cluster are 8.1 L on the left and 10.8 L on the right.


Will keep everyone updated.


Thanks again
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post #12 of 47 Old 29th March 2019, 03:13 PM Thread Starter
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Originally Posted by M3Fan View Post
FWIW I used this guy for my injector cleaning and he did a great job. Very thorough and knowledgable, quick, easy to deal with. http://roschfuelinjectorcleaning.com/place-orders/

Thanks for the info!!!
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post #13 of 47 Old 29th March 2019, 04:14 PM
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Garage
I'm betting on fuel filter and/or pump. Those other items should be done anyway as PM.

Keep us posted!

Tim

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post #14 of 47 Old 29th March 2019, 04:47 PM
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No load higher RPM misfires are probably going to be vanos or air measuring related. The DME swings pretty lean in no load off throttle cases.

I had a similiar issue a while back, nice and warm engine off throttle at about 4k it would start missing and drop into cut out, playing around was able to correct it by adding a hair more fueling and it went a way. So I started down the fuel air path, instead of spark, decided to run the vanos test and it failed. Turned out to be problem.

At the very least I'd run the vanos test before throwing parts at it.

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Last edited by Ferris; 29th March 2019 at 04:47 PM.
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post #15 of 47 Old 29th March 2019, 05:28 PM
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Quote:
Originally Posted by SupercarFreak View Post


Fuel tank levels in the cluster are 8.1 L on the left and 10.8 L on the right.

Here is a free test. Problem is my memory, the details might not be right but you will still get the concept. I am assuming what I quoted was with the car off, if it was running you might have problems. Look at the same function in the OBC, start the car the and let it idle, you should see the fuel transfer from the left to right tank at a rate of 2l/min(???). I wrote about the rate and tested this many times, but I am not sure I remember the correct numbers.

That test gives you a ton of info and the rate is easy to confirm by others if need be. Not only does it test the jet pump system, but it also tests how strong your fuel pump is and if your filter is plugged up. It does not tell you specifically what is wrong, you will need more tests but it is a great place to start.
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post #16 of 47 Old 29th March 2019, 05:41 PM Thread Starter
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Quote:
Originally Posted by Ferris View Post
No load higher RPM misfires are probably going to be vanos or air measuring related. The DME swings pretty lean in no load off throttle cases.

I had a similiar issue a while back, nice and warm engine off throttle at about 4k it would start missing and drop into cut out, playing around was able to correct it by adding a hair more fueling and it went a way. So I started down the fuel air path, instead of spark, decided to run the vanos test and it failed. Turned out to be problem.

At the very least I'd run the vanos test before throwing parts at it.

Thanks Ferris. Ripped all the old parts out of the car this morning. Once the new parts are in, if it misfires again I'll take it to the dealer to perform the VANOS test and if it fails that I'll rebuild the units myself with the Besian kit.


On a side note, KW Variant 1's are AWESOME.


My thrust rod bushings are leaking so I have Moosehead spherical bushings mounted in new Lemforder arms on the way. I don't have a hydraulic press and the ball joint boots are torn so figured I'd replace the arms as well.
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post #17 of 47 Old 29th March 2019, 05:46 PM Thread Starter
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Quote:
Originally Posted by Sailor24 View Post
Here is a free test. Problem is my memory, the details might not be right but you will still get the concept. I am assuming what I quoted was with the car off, if it was running you might have problems. Look at the same function in the OBC, start the car the and let it idle, you should see the fuel transfer from the left to right tank at a rate of 2l/min(???). I wrote about the rate and tested this many times, but I am not sure I remember the correct numbers.

That test gives you a ton of info and the rate is easy to confirm by others if need be. Not only does it test the jet pump system, but it also tests how strong your fuel pump is and if your filter is plugged up. It does not tell you specifically what is wrong, you will need more tests but it is a great place to start.

Thanks Sailor, that is a great idea. I will do this once the car is drivable again
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post #18 of 47 Old 29th March 2019, 06:36 PM
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post #19 of 47 Old 29th March 2019, 11:37 PM
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I am gonna use Occam's razor here and call it all (at least most) due to a dying fuel pump which will be worse at lower tank levels, give you the misfire with empty tank code, misfire codes, and O2 sensor codes (reporting lean).
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post #20 of 47 Old 30th March 2019, 07:11 PM Thread Starter
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Great looking beast, and a nicely appointed garage!

--Peter
Thanks Peter I really appreciate it 😎
Been here for about a year now and I pretty much have it set up just how I want. Took a lot of time and money but I’ve always dreamed of having a shop at my house!

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I am gonna use Occam's razor here and call it all (at least most) due to a dying fuel pump which will be worse at lower tank levels, give you the misfire with empty tank code, misfire codes, and O2 sensor codes (reporting lean).
Thanks for the input. What you said makes perfect sense and I wouldn’t be surprised if it ends up being the fuel pump. I will keep everyone updated.

Last edited by SupercarFreak; 30th March 2019 at 07:12 PM.
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