Misfires only at high rpm WOT

zomski101

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Dec 28, 2019
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If anyone can help me out I am getting random misfires at WOT at high rpm on random cylinders. I am running a flex fuel tune by a very well known tuner. When I have less ethanol than e50 the car pulls all the way to redline with no misfires, but when I fill up with more than e50 I sometimes get misfires above 6800rpm and when I put more than e60 it happens sooner in the rpm all the times only at WOT tho.

Car is a 2009 335i AT, I have mmp stage 3 turbos, FBO, PR coils, helix 3x, stage 3 lpfp and BPM4.

Tuner lowered boost slightly but same thing.
I replaced ngk 97506 gapped at .022 with new ones gapped to .018
switched around coils
6 new index 12 injectors and coded
replaced valve cover, lpfp sensor, all 4 o2 sensors and battery
Compression is around 165-170

At this point, if someone has a suggestion that will solve this im willing to paypal 50 buck.

e42 all good:

e53 all good:

e53 misfire on cylinder 5 in 4th gear at 6500rpm:

e70 misfire on cylinder 1 and 3 in 3rd gear at 6800rpm:
 

NoGuru

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Jan 9, 2018
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.018 is pretty tight unless you think you are in the 700+ range.
Might have to inspect the plug boots. Also make sure the plugs are still tight. I have heard of them coming lose depending on which plugs you run.
 

zomski101

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Dec 28, 2019
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.018 is pretty tight unless you think you are in the 700+ range.
Might have to inspect the plug boots. Also make sure the plugs are still tight. I have heard of them coming lose depending on which plugs you run.
Reason for going from .022 to .018 gap was strictly to rule out if that was the issue, plus put dielectric grease on the ceramic part of the plug and inside boot. I doubt the boots are the issue, I made sure they were clicked in and put a good portion of my weight on them. Also, misfires happen on multiple random cylinders, today I did a pull and got a misfire on cylinder 6.
 

NoGuru

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Reason for going from .022 to .018 gap was strictly to rule out if that was the issue, plus put dielectric grease on the ceramic part of the plug and inside boot. I doubt the boots are the issue, I made sure they were clicked in and put a good portion of my weight on them. Also, misfires happen on multiple random cylinders, today I did a pull and got a misfire on cylinder 6.
Okay, this one is going to be hard to track down. I would make a list of things you can rule out for sure and see what is left.
And the tuner has no idea?
I don't know that much about the BMP4 but does that get tuned?
 

houtan

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Nov 2, 2017
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Look at your rail pressure. It’s drops as your rpms go up. Is this what the tuner is telling the tune to do?

I’m early n55 but when my rail pressure dips like that, even though it’s not below 2k, I get misfires.
 

zomski101

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Dec 28, 2019
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Your bank 1 and bank 2 stft at 6500 seems to have too much of a diff...
Yeah, bank 2 stft seems to go to max at higher rpm as ethanol content increases. Bank 2 also seems leaner, but I get misfires on bank 1 consistently now, sometimes on cyl 5 or 6 when I filled up on e70 today.
 

zomski101

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Dec 28, 2019
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Decided to pull injector 6 today and put teflon tape and found this. Any thoughts on what this means, obviously it's not normal.
 

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iminhell1

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Jun 17, 2018
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Put Teflon tape?
As some kind of hobo gasket? Don't do that. No good will come of it.


So, the way spark plugs work is they have to remain hot enough after ignition to burn off contaminates but cold enough as to not overheat (which raises resistance and can cause pre-ignition if very hot). There is a time variable her also, the more time between ignition events, the longer the plug has to bleed excess heat. And the closer, higher RPM, the less time there is to bleed heat.
This is where the hot and cold plug comes into play. Pull plugs and see if they are overheating, and double check the gaps.
The ground strap discoloration with indicate ignition timing. You want the color change to be near the bend.
The color change on the threads will indicate the plug temp. Generally 2 threads should show color change.
Yes you can mix and match heat ranges. It's not common, but on engines with some age it'd be more common.
 

zomski101

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Dec 28, 2019
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Pulled the plugs, I see timing marks on the last pic which is cylinder 1. Pics 2 and 3 are from cylinder 6.
 

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iminhell1

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Jun 17, 2018
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Pull 1* from the top end, timing.
The bottom plug in the of 6 pic, has been sitting in water / was wet at some point. I'll bet that's #6 and you have BMS filters and no engine cover. Carwash/rain will drip into #6 and cause havoc.
Heat range looks OK.
 
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Torgus

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Nov 6, 2016
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Pull 1* from the top end, timing.
The bottom plug in the of 6 pic, has been sitting in water / was wet at some point. I'll bet that's #6 and you have BMS filters and no engine cover. Carwash/rain will drip into #6 and cause havoc.
Heat range looks OK.

My thoughts exactly.

Also, that injector looks f'd. Could that crap be the coolant from inside the injector?
 

iminhell1

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Jun 17, 2018
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My thoughts exactly.

Also, that injector looks f'd. Could that crap be the coolant from inside the injector?


No that's the teflon tape he wrapped around it for who knows why.
Might have nicked the seal or scared the bore and now it's leaking a little compression.
New seal would be a good idea ... I do new seals any time I pull my injectors.
 

zomski101

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Dec 28, 2019
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No that's the teflon tape he wrapped around it for who knows why.
Might have nicked the seal or scared the bore and now it's leaking a little compression.
New seal would be a good idea ... I do new seals any time I pull my injectors.
I did not put any teflon or material on the injector. That is what I found when I pulled it out. Injector only had 2000 miles on it. The reason I was going to put teflon tape was to create a better seal, considering the engine has 175k miles on it. Just ended up putting it back in.

Pull 1* from the top end, timing.
The bottom plug in the of 6 pic, has been sitting in water / was wet at some point. I'll bet that's #6 and you have BMS filters and no engine cover. Carwash/rain will drip into #6 and cause havoc.
Heat range looks OK.
That was from cylinder 1 I still have the cowl and engine cover. Pulled 6 degrees of timing and it's still misfiring.
 

chrisuan

New Member
Nov 14, 2020
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Have you solved this issue? I'm running into the same problem. Random misfires only on WOT. So frustrating! Ive got new plug, coils, injector index12, lpfp sensor, etc...