135i misfire when high boost

[awesomexy135]

Hi, everyone, I am having weird misfire with my 135i, the car is 6AT, when the boost is over 15psi, the car will shake and give me the code cylinder 3 and 4 misfire. and I swapped coil and changed plugs, still having this problem. right now it is using MHD STAGE 1, I have upgraded intercooler, downpipe, intake, charge pipe and BOV.
I checked logs and the target boost and actual boost are very close.

need help, thank you everyone.

[Soterios]

What fuel are you running?

Can you log? What are your injectors/fuel pump doing?

[HyeWarrior]

Similar thing happened to me not long ago on MHD stage 2. I was also on fresh coils/sparkplugs. Turned out that 2 of the coils were defective.

[awesomexy135]

Originally Posted by Soterios

What fuel are you running?

Can you log? What are your injectors/fuel pump doing?

https://drive.google.com/file/d/1W9t...ew?usp=sharing

this is the link to my data logging,
index 12 injectors
Fuel-It Stage one pump

[awesomexy135]

Originally Posted by HyeWarrior

Similar thing happened to me not long ago on MHD stage 2. I was also on fresh coils/sparkplugs. Turned out that 2 of the coils were defective.

i have ever swap the coil around each cylinders, but it doesn't change anything, still cylinder 3 and 4 misfire

[dizzy619]

Originally Posted by awesomexy135

i have ever swap the coil around each cylinders, but it doesn't change anything, still cylinder 3 and 4 misfire

Take a plug out on those cylinders and see if they are wet..

[iminhell1]

Your fueling is waaaay off.
Lambda is all over the place, even before your 15psi limit.

#36 is your exit of "lean spool", after that look at your 'short term' fuel trims. See how they are negative numbers, that's the car pulling fuel because it's overly rich.
This could be something within the tune or (and more likely) a boost leak.
Pressure test the intake and find/fix the leak.

Also have to ask if the injectors where coded properly, where seals installed correctly, did they seat?

[awesomexy135]

thank you everyone.
I think I just fixed the misfire. I just tested it, right now it is 20psi without misfire. turns out, there is a round plastic thing on the charge pipe and it hooked to power source, I don't know what it is, after I unhooked power source from it. the misfire was gone.

again thank you everyone for the help.

[iminhell1]

Well,
That is a Hobb's Switch.
It's used in conjunction with that braided hose on top of the throttle body for Methanol Injection.

Now seeing that, you should have some knowledgeable local look the car over. Seems there is more done than you know about. Best to find out before any more problems arise.

[Soterios]

Originally Posted by iminhell1

Well,
That is a Hobb's Switch.
It's used in conjunction with that braided hose on top of the throttle body for Methanol Injection.

Now seeing that, you should have some knowledgeable local look the car over. Seems there is more done than you know about. Best to find out before any more problems arise.

Agreed.

"Unplugged unknown thing" isn't a great solution. (even if it ends up being the solution, if that makes sense)