[Fallenangel123]

Hey everyone,

I recently had cold start rough idle / misfire issues. Injector 1 was leaking fuel on to the spark, and the valve cover gasket was leaking. As a result I changed the following:

Bank 1 (3 x Index 12 Injectors, Coded using INPA)
6x OEM Spark Plugs
6x Eldor Coils
New Valve cover, gasket, and screws
New crank case hose
This fixed the cold start misfires.

A week or two later I began to notice the car shaking at idle / hiccups, since then I have done and verified the following:
MHD Reset Adaptations
HPFP Rail Pressure is healthy at idle and WOT
WOT Logs seem healthy : Log here for reference: https://datazap.me/u/fallenangel123/...og=0&data=3-21
Checked the spark plugs for any sign of fuel / oil
Verified the sparks are torqued correctly, and the coils seated correctly
Inspected ignition wiring
Car runs great at WOT, but terrible at idle
Car is throwing no codes

I have also created some logs under regular driving with idle conditions when the car was misfiring, viewable here: https://datazap.me/u/fallenangel123/...0&data=2-14-15
Are these spikes in AFR normal?

Could anyone please advise if they can see anything obvious in the logs that could help diagnose the issue? It is driving me crazy!

Thanks

[CarAbuser]

The spikes in AFR coincide with you letting off the accelerator pedal. It's normal for fuel injection to stop on overrun. Both banks seem to follow each-other tightly which is a good indicator of healthy injectors.

I think it's probably the wrong terminology to call them misfires but I know what you mean. These shakes at idle are common. Have a look through this thread: https://www.e90post.com/forums/showthread.php?t=571344

As I said on the Z4 forums, it's most likely plugs. When BMW did all my servicing this was an issue that seemed to crop up after spark plug changes and only really go away after they were changed again. The most recently service I changed to NGK 5992 plugs and fastidiously gapped them myself and the problem is not present.

[Fallenangel123]

Originally Posted by CarAbuser

The spikes in AFR coincide with you letting off the accelerator pedal. It's normal for fuel injection to stop on overrun. Both banks seem to follow each-other tightly which is a good indicator of healthy injectors.

I think it's probably the wrong terminology to call them misfires but I know what you mean. These shakes at idle are common. Have a look through this thread: https://www.e90post.com/forums/showthread.php?t=571344

As I said on the Z4 forums, it's most likely plugs. When BMW did all my servicing this was an issue that seemed to crop up after spark plug changes and only really go away after they were changed again. The most recently service I changed to NGK 5992 plugs and fastidiously gapped them myself and the problem is not present.

Hey mate, thanks for the input once again.
Edit: I see what you mean regarding users complaining of this after changing plugs. Where did you get your NGK spark plugs from, Struggling to find them anywhere in the UK atm
Second edit: Car is "shaking" at idle of 650rpm, goes away when idle is @ 750rpm with ac on.

[Fallenangel123]

So I have just been out for a long drive, the car does seem better. How ever I also noticed this

When the car is idling @ 650rpm, it feels shaky
If I turn AC on and it idles @ 750rpm it feels silky smooth

Any ideas on why this might be guys?

[Antetokounmpo]

Originally Posted by Fallenangel123

So I have just been out for a long drive, the car does seem better. How ever I also noticed this

When the car is idling @ 650rpm, it feels shaky
If I turn AC on and it idles @ 750rpm it feels silky smooth

Any ideas on why this might be guys?

I actually kinda had the same issue on mine.. not kidding when I went to catless downpipes the car idled MUCH smoother. Not saying it's your issue but it could be a multitude of things.

[Fallenangel123]

Originally Posted by Antetokounmpo

I actually kinda had the same issue on mine.. not kidding when I went to catless downpipes the car idled MUCH smoother. Not saying it's your issue but it could be a multitude of things.

Hey, well hopefully they help! Having catless downpipes fitted next week so will report back any change

[Jeff@TopGearSolutions]

3 index 12 injectors? What are the other injectors? If not index 12 that may be your issue.

Also, I noticed no fuel low pressure psi seems to be reading.

Any other codes?

[Fallenangel123]

Originally Posted by Jeff@TopGearSolutions

3 index 12 injectors? What are the other injectors? If not index 12 that may be your issue.

Also, I noticed no fuel low pressure psi seems to be reading.

Any other codes?

Bank 1 has 3 index 12 Injectors
Bank 2 has 3 index 07 Injectors

My car is a Z4 35is, which has no LPFP

Unfortunately no codes have been logged, checked via MHD

[Fallenangel123]

Further update:
Car is misfiring at idle still, especially when starting warm or cold. I have embedded some pictures of the piston heads below, I am not to familiar in what I should be looking for on the piston heads, but I am hoping someone on here is, and perhaps could provide some clues.

Thanks!

Pictures below:
Piston 1

Piston 2

Piston 3

Piston 4

Piston 5

Piston 6

[JuniorB]

By looking at these, it looks like the oil deposits are on the intake side. I can't see the arrow,,and I don't have a piston in front of me, but by looking at this, you need a walnut blast, and possibly your intake cleaned of all the oil that's in in. The oil deposits would be diluted and cleaner by burning off , if you had a bad injector. I'd pull the intake and look inside everywhere.

[RoughKnight]

Yo, same thing is happeneing with my car kinda. Flash the 7.1 and try it again, see if you dont get the throttle cut. Your logs look exactly like my 8.0 logs and I get the throttle cut up in the rpm range like you. Put it back to 7.1 burble on and poof back to normal and full power.

[CarAbuser]

Have you taken a look at your intake valves?

[NoGuru]

Could be your O2's.

[dpaul]

Originally Posted by NoGuru

Could be your O2's.

Could be the phase of the moon

[Fallenangel123]

Originally Posted by CarAbuser

Have you taken a look at your intake valves?

I have some NGK 95770's on the way. I am going to gap those at 0.022 and install them tomorrow. I am hoping that cures the issue, if it does not I will be moving on to the intake valves / walnut blasting. Will report back

Originally Posted by RoughKnight

Yo, same thing is happeneing with my car kinda. Flash the 7.1 and try it again, see if you dont get the throttle cut. Your logs look exactly like my 8.0 logs and I get the throttle cut up in the rpm range like you. Put it back to 7.1 burble on and poof back to normal and full power.

I have gone back to V7 as I was overboosting on V8. I have also turned off the burble so the car doesn't run so rich.

Originally Posted by NoGuru

Could be your O2's.

Possibly, but given that this only occurs at idle, surely if it was 02's I would also see problems at WOT / all through the rev range?

Originally Posted by dpaul

Could be the phase of the moon

lmao

[Red_Tears]

Try cleaning your VANOS solenoids, I had an 07 328 that did the exact same thing and I went through spark plugs, coils, even a MAF sensor before I figured it out.

Cleaning is generally not a cure-all though so if it does seem to run better afterwards you need to get your hands on some new ones.

Nathan's BMW workshop has a video where he had the issue on a 328 as well, for reference.

Good luck I hope you can figure it out!

-R

Edit: Cleaning may not solve the issue so if you have a local salvage yard or a very nice buddy with a similar car you can swap them with those to check.

[CarAbuser]

Originally Posted by Fallenangel123

I have gone back to V7 as I was overboosting on V8. I have also turned off the burble so the car doesn't run so rich.

The burble is something which occurs on the stock map with the Z4, all MHD will do is allow you to reduce timing further to make louder pops. It doesn't enrich anything.