[tpoddar]

Hey guys,
I'm having a ton of issues with my B48 320i. A short timeline -
2020 - Tuned Car with bm3
August 2022 - Start having extreme misfires on my car. Tested compression (all good), plugs and coils. Two coils were bad and all 4 plugs were fouled. Plugs and coils were replaced with brand new OEM parts brought from the dealer. Issue resolved and sticking to stock tune. (KMS - 64xxx)
Jan 2022 - I tune the car again. After a couple of hundred kms, same misfiring and all 4 plugs are black and wet (pics below). I clean the plugs, check the coils and switch back to the stock tune (just to test) it no longer misfires. (KMS - 65xxx)



Now, (1/8/23) my car is still misfiring 1.5k-2k rpms under low loads and it feels like it's bucking. It also occassionally shakes on startup. There are absolutely no codes which is making diagnosis impossible. Any help would be appreciated. Here are some logs that I have collected -
WOT Logs:
Stock (Dec) - https://www.bootmod3.net/log?id=63ac...729b5993cc32fa
Stage 2 (August) - https://www.bootmod3.net/log?id=62e4...729b2d5d51d863
Part Throttle Logs:
Stock (Jan) - https://www.bootmod3.net/log?id=63b5...0b43b9c3cb1c8b
Stage 2 (Dec) - https://www.bootmod3.net/log?id=63ab...0b43b638c3fdd4

[jcdub]

Run the engine at idle and open the oil filler cap. Check if there is pressure coming from the rocker cover...

[tpoddar]

Originally Posted by jcdub

Run the engine at idle and open the oil filler cap. Check if there is pressure coming from the rocker cover...

If there is pressure, what does it mean? If there's no pressure, what can be the issue? My compression test is good btw just tested yesterday. I also have zero oil consumption between changes (5k miles) and no other mechanical issues other than the misfires and shaking.

[hEllberg]

Originally Posted by tpoddar

If there is pressure, what does it mean? If there's no pressure, what can be the issue? My compression test is good btw just tested yesterday. I also have zero oil consumption between changes (5k miles) and no other mechanical issues other than the misfires and shaking.

So the car runs fine for a while after changing plugs/cleaning, and then they become black and wet? Does it looks like oil on the plugs? Your compression test being good kind of kills the theory of worn rings. Was there any oil on top of the plugs when you removed them, could be that the rocker cover gasket is shot?

[tpoddar]

UPDATE: I ran a misfire test on ista and this was the result -


I'm gonna inspect the plug in cylinder 4 and replace the coil. I'll run the test again and if the result stays the same, I'll switch the cylinder 4 injector. Car is running fine for now.

[tpoddar]

I Moved coils and cleaned plugs before running the test again. The test passed with no problems. Cylinder 4 plug had a bit of fuel on the tip. There was a bit of oil on the threads too. A mixture of oil and fuel seems to be fouling plugs without reason. Any ideas?

[tpoddar]

Originally Posted by hEllberg

So the car runs fine for a while after changing plugs/cleaning, and then they become black and wet? Does it looks like oil on the plugs? Your compression test being good kind of kills the theory of worn rings. Was there any oil on top of the plugs when you removed them, could be that the rocker cover gasket is shot?

There was oil on the threads but not on the outside of the plug. Compression is good and the fouling is occurring across all 4 cylinders which makes me question what it could be. Ideas?

[tpoddar]

I had the valve cover changed but still there's oil fouling on plugs. Cylinder 4 is most affected. Compression was tested by the dealer and it's still good at 220psi (15 bar). The dealer neither has a borescope nor does he have leak down testing equipment. Is there any other way of testing if it's the rings/valves or maybe scored cylinders?

[tpoddar]

UPDATE: I did a leakdown test and all cylinders had less than 5-6% leakage. Injectors were taken out and also tested for leaks, no issues found. What else could it be?

[Eddamoo]

One message says fuel on the plugs and your latest days oil fouling. Can you confirm which it is, as fuel would clean off oil.

If it's oil fouling, I would be looking at the pcv as a possible culprit. With oil vapor being relatively heavy, it may have an easier path into Cyl4 dependant on the inlet manifold and throttle body position.

Did you check the crank case pressure with the oil cap off?

[tpoddar]

Originally Posted by Eddamoo

One message says fuel on the plugs and your latest days oil fouling. Can you confirm which it is, as fuel would clean off oil.

If it's oil fouling, I would be looking at the pcv as a possible culprit. With oil vapor being relatively heavy, it may have an easier path into Cyl4 dependant on the inlet manifold and throttle body position.

Did you check the crank case pressure with the oil cap off?

Hey, it's 100% oil on the plugs. I got the valve cover changed suspecting a PCV issue but that's about all I did. Crankcase pressure seems okay, maybe a bit high. How should I check the other PCV components?

[tpoddar]

Hey guys,
I've had the valve cover, piston rings and valve seals replaced but the car started to misfire again after 200-300kms. I'm now looking at fueling components since oil shouldn't be a possibility post so many repairs. Except for injectors and o2 sensors, is there anything else that I should check?

[Zrob]

tpoddar any updates?

Im having a very simiplar problem with my 320i 2016. Changed sparkplugs ,coils, vanos solenoids, tank breather valv, cleaned MAF and MAP.
Sometimes having code P0301 , p0304 and p0300 then they dissipears. But always small misfireing and a bit strutter on idle, weak under 2000rpm.

[tpoddar]

Originally Posted by Zrob

tpoddar any updates?

Im having a very simiplar problem with my 320i 2016. Changed sparkplugs ,coils, vanos solenoids, tank breather valv, cleaned MAF and MAP.
Sometimes having code P0301 , p0304 and p0300 then they dissipears. But always small misfireing and a bit strutter on idle, weak under 2000rpm.

Did you check your spark plugs? Can you share any pictures? Is your car tuned?

[Zrob]

I changed plugs for the second time this weekend, I suspected that I did overtorque last time - had no torquewrench. So now - new oem Ngk plugs at 23nm. Still same problem.
Plugs look rater good I think!? Or?

[Zrob]

I did a live capture by a friends budget obd scanner and got some values both when no errorcodes are present and when i got P0300, P0301, P0304.
Did a summery of the values that does differ.

Does this tell you guys something?
Could it be a 02 sensor that is bad?

[sqwinny]

A 2016 320i should be an n26.

If you did plugs and coils, the only thing left is fuel injectors. If you replaced those and didn’t code them to the car, that’s a high chance where your issue is.

first I'd clean the MAF sensor and ensure the upper oxygen sensor isnt giving false readings.

Very rare for the high pressure fuel pump or low pressure fuel pump to be the issue here.

As always, check for boost leaks as well

[MagnusAG99]

Originally Posted by sqwinny

A 2016 320i should be an n26.

If you did plugs and coils, the only thing left is fuel injectors. If you replaced those and didn’t code them to the car, that’s a high chance where your issue is.

first I'd clean the MAF sensor and ensure the upper oxygen sensor isnt giving false readings.

Very rare for the high pressure fuel pump or low pressure fuel pump to be the issue here.

As always, check for boost leaks as well

LCI F30 320i only came with the N20/N26 in the US, in all other countries the LCI has the B48. I have no idea why BMW decided to keep the N20/N26 in the F30 LCI only the US market.

[sqwinny]

Originally Posted by MagnusAG99

LCI F30 320i only came with the N20/N26 in the US, in all other countries the LCI has the B48. I have no idea why BMW decided to keep the N20/N26 in the F30 LCI only the US market.

Perhaps. Confirmed you are right by typing the part number off the spark plugs above.
Either way all the issues TPodder had was clogged/leaking fuel injectors. Unfortunately they didn’t want to change/check the fuel injectors and took their entire motor apart. After all the $$$ and time and effort, it was the fuel injectors.