SOLVED Misfires on cyl 6 on heavy load - Z4 35is MHD 2+

[Peter55]

Hey guys, I'm trying to solve misfires on cyl 6 on heavy loads.

My car is Z4 E89 35is with DCT and around 80k mileage.

Problem started to show after stage 2+ from mhd, it appears on continuous heavy load (flooring) and higher gears. I noticed it more often on hot day.

I've done the following since then:
1. NGK 97506 spark plugs with 0.020'' gap
2. New Delphi coils
3. Walnut blast intake port cleanup
4. Injector check for leaks - no leaks, new seals and replaced cyl 6 with cyl 2 - still misfire on 6
5. Walbro 450 lpfp
6. EKP with additional themopads (didn't know walbro 450 overheats ekp)
7. 3.5 bar map sensor with flashing

I plan to go with single turbo setup, so I'd done those things either way.

Additional mods:
1. Wagner Evo 3 IC
2. Catless downpipes
3. DCI
4. MHD + xhp
5. Vrsf charge pipe with HKS bov
6. Golf tee mod, exhaust flap can't close so I've plugged the vacuum hose for now

I've checked the compression on cold motor, here are the results:
1. 159.5 psi
2. 181.3 psi
3. 181.3 psi
4. 159.5 psi
5. 177.0 psi
6. 181.3 psi

Logs with pulls (no missfire errors): log1 log2
Log on stationary with small load increase: log

My suspision is hpfp, in my opinion repeating misfire on 6 cyl could be caused by the lack of fuel pressure.
I wanted to ask - is there something in logs to support that? Or something I should have check before hpfp change?

Another issue are high LTFT on idle, around 20% on bank 1 and over 20% on bank 2 - here I also suspect hpfp or walbro 450 messing with EKP settings. That one came recently.

May I ask for some help from you?

 

[Peter55]

@Peter55 hi did you ever get this situation resolved? I recently did a bolt on with 14T Turbo upgrade and now if misfire on cylinder 6 at heavy load. Error code are 29D2 and 29D9.

Hey, right now I'm doing rebuild and I bought flywheel from M4 - as I thought mine was in very bad shape - I hope that'll resolve the issue!

 

[longjonsilva]

Should prob check condition of rod bearings too at some point.

 

[Peter55]

DCT has a dual mass flywheel and the bushing tend to wear out and create vibrations in the higher RPM's.

I had this issue and installed an M4 single mass and it resolved the misfire.

UPDATE
After replacing flywheel car no longer missfires on cylinder number 6, old one was indeed worn out.

Thanks to all for suggestions!
Switching injectors, plugs and coils plus compression test with correct rail pressure should have been enough evidence that flywheel was faulty.

Right now I'd like to sort out high LTFT, but I'll start another topic for it.

 

[pbondar]

UPDATE
After replacing flywheel car no longer missfires on cylinder number 6, old one was indeed worn out.

Thanks to all for suggestions!
Switching injectors, plugs and coils plus compression test with correct rail pressure should have been enough evidence that flywheel was faulty.

Right now I'd like to sort out high LTFT, but I'll start another topic for it.

Great to know…I have a new one sat on my bench awaiting being brave..