[Solved] Cylinder 2 misfire after fixing oil leak

lynn · 09-11-2023, 05:51 AM

Hi there, long time lurker, first time poster.

Picked up my E92 back in March this year with 160k kms. Only had a few wheel speed issues up to now. I had some mates over on Sunday to help me tackle an oil leak from the oil filter housing and valve covers. I thought that since we had to pull the valve covers off, now would be a good time to do the spark plugs as they were last changed in 2016.

After putting everything back together, filling up the engine with new oil and coolant. Starting the car the first time since Sunday threw a check engine light at me and reduced power output

.
My scan tools shows 3 fault codes from the engine management, they are as follows:

2B57 Air-mass sensor, plausibility
275A Ignition circuit, cylinder 2
2796 Throttle actuator-test, lower stop

I swapped the coil pack between cylinder 1 and 2, cleared the codes and still got the same result above. Tried swapping the spark plug for one of the old ones, the same again. I also tried retorquing the spark plug thinking it just wasn't seated correctly but that didn't do anything different either.

Lastly I tried swapping the coil plug for cylinder 1 into cylinder 2, leaving cylinder 1 disconnected. This produced more fault codes that related to cylinder 1 misfiring, but also cylinder 2 and 3. The cylinder 2 code was also different to above.

I'm out of ideas here, I doubt my throttle actuators have suddenly gone bad all of a sudden. I struggle to get the plenum seated correctly sometimes as well, and I've had a misfire on cylinder 8 before after seating the plenum. But that was only at redline so like 8k rpm and I was hesitant to fix it asap (it did get fixed by either me or a shop who diagnosed my oil leak).

I'm curious if anybody has any paths they can point me to before I give up and have a mechanic to take a look.

Cheers

Update: I posted below what the problem is. tldr; fuel leak caused low fuel pressure, and reseating the coils was enough to fix the misfires.

lynn · 09-11-2023, 05:58 AM

I've also checked the ground terminals for the cylinder bank and confirmed that they're grounded and secured. I read another forum post that mentioned misfires of an entire bank of cylinders because of the ground terminals, but only one cylinder misfiring wouldn't point to that being the problem.

gh0stE92M3 · 09-11-2023, 08:41 AM

So I had this same issue not to long ago, there’s some ground wires behind the valve covers closer to the firewall that might be loose, mine was slightly loose and that fixed the issue. I was getting the same codes. I was getting cylinder 2/3 misfires. Pretty much went through the same thing you did swapped coils around and new spark plugs. But it was literally one of the ground cables slightly loose.

lynn · 09-12-2023, 01:30 AM

Got an update on this,

Took the car to a shop since I'm out of ideas, tried ghost's suggestion above but the ground terminals look fine. Turns out my injector's were leaking, o-rings were shot and need to be replaced. 3 day wait on the parts since they have to ship them up from Sydney to Brisbane (Australia). The tech doesn't know if this will fix the misfire or not, maybe it will since it could be a fuel pressure problem?

kolosy · 09-12-2023, 10:23 AM

i'd scope the block and check for cylinder scoring. depending on how the injectors leak, they could wash out cylinder walls.

charliev68 · 09-12-2023, 11:48 AM

Valve Spring. Do a leak down test and bore scope the cylinder

lynn · 09-17-2023, 06:07 AM

Forgot to update this thread sooner, for anybody paying attention for the fix. The fuel leak from the injectors were the main culprit, as was the fuel hose that connects the left and right banks. The shop wasn't able to order the hose as a new part, BMW only sells the entire fuel rail assembly and I wasn't going to pay 1300$ for a new rail. They replaced the rubber part with a metal piece so the fuel rail is all metal now.

After fixing the fuel leaks, cyl 8 started throwing misfire codes as was cylinder 6. So the shop played around with the coils, reseating them. That did it and the engine runs smoothly.

So my recent work fixing the oil leak cost me an extra 1200$ I didn't budget for haha.

09-11-2023, 05:51 AM	#1
lynn New Member 21 Rep 11 Posts Drives: M3 E92 Melbourne Red Join Date: Sep 2023 Location: Brisbane iTrader: (0)	[Solved] Cylinder 2 misfire after fixing oil leak Hi there, long time lurker, first time poster. Picked up my E92 back in March this year with 160k kms. Only had a few wheel speed issues up to now. I had some mates over on Sunday to help me tackle an oil leak from the oil filter housing and valve covers. I thought that since we had to pull the valve covers off, now would be a good time to do the spark plugs as they were last changed in 2016. After putting everything back together, filling up the engine with new oil and coolant. Starting the car the first time since Sunday threw a check engine light at me and reduced power output . My scan tools shows 3 fault codes from the engine management, they are as follows: 2B57 Air-mass sensor, plausibility 275A Ignition circuit, cylinder 2 2796 Throttle actuator-test, lower stop I swapped the coil pack between cylinder 1 and 2, cleared the codes and still got the same result above. Tried swapping the spark plug for one of the old ones, the same again. I also tried retorquing the spark plug thinking it just wasn't seated correctly but that didn't do anything different either. Lastly I tried swapping the coil plug for cylinder 1 into cylinder 2, leaving cylinder 1 disconnected. This produced more fault codes that related to cylinder 1 misfiring, but also cylinder 2 and 3. The cylinder 2 code was also different to above. I'm out of ideas here, I doubt my throttle actuators have suddenly gone bad all of a sudden. I struggle to get the plenum seated correctly sometimes as well, and I've had a misfire on cylinder 8 before after seating the plenum. But that was only at redline so like 8k rpm and I was hesitant to fix it asap (it did get fixed by either me or a shop who diagnosed my oil leak). I'm curious if anybody has any paths they can point me to before I give up and have a mechanic to take a look. Cheers Update: I posted below what the problem is. tldr; fuel leak caused low fuel pressure, and reseating the coils was enough to fix the misfires. Attached Images Last edited by lynn; 09-17-2023 at 06:08 AM..
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09-11-2023, 05:58 AM	#2
lynn New Member 21 Rep 11 Posts Drives: M3 E92 Melbourne Red Join Date: Sep 2023 Location: Brisbane iTrader: (0)	I've also checked the ground terminals for the cylinder bank and confirmed that they're grounded and secured. I read another forum post that mentioned misfires of an entire bank of cylinders because of the ground terminals, but only one cylinder misfiring wouldn't point to that being the problem.
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09-11-2023, 08:41 AM	#3
gh0stE92M3 Second Lieutenant 159 Rep 210 Posts Drives: BMW E92 M3 Join Date: May 2020 Location: California iTrader: (1)	So I had this same issue not to long ago, there’s some ground wires behind the valve covers closer to the firewall that might be loose, mine was slightly loose and that fixed the issue. I was getting the same codes. I was getting cylinder 2/3 misfires. Pretty much went through the same thing you did swapped coils around and new spark plugs. But it was literally one of the ground cables slightly loose.
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09-12-2023, 01:30 AM	#4
lynn New Member 21 Rep 11 Posts Drives: M3 E92 Melbourne Red Join Date: Sep 2023 Location: Brisbane iTrader: (0)	Got an update on this, Took the car to a shop since I'm out of ideas, tried ghost's suggestion above but the ground terminals look fine. Turns out my injector's were leaking, o-rings were shot and need to be replaced. 3 day wait on the parts since they have to ship them up from Sydney to Brisbane (Australia). The tech doesn't know if this will fix the misfire or not, maybe it will since it could be a fuel pressure problem?
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09-12-2023, 10:23 AM	#5
kolosy Colonel 1493 Rep 2,022 Posts Drives: over potholes Join Date: Dec 2008 Location: Chicago iTrader: (2)	i'd scope the block and check for cylinder scoring. depending on how the injectors leak, they could wash out cylinder walls. __________________ Current '21 DG X5MC, '22 X5M50i, '11 E90 M3 Recent Past '12 E92 M3 ZCP, '08 E93 M3, '18 F80 ZCP, '04 E46 M3 I think I have an M3 problem.
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09-12-2023, 11:48 AM	#6
charliev68 Second Lieutenant 204 Rep 203 Posts Drives: bmw m3 Join Date: Feb 2020 Location: CA iTrader: (1)	Valve Spring. Do a leak down test and bore scope the cylinder
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09-17-2023, 06:07 AM	#7
lynn New Member 21 Rep 11 Posts Drives: M3 E92 Melbourne Red Join Date: Sep 2023 Location: Brisbane iTrader: (0)	Forgot to update this thread sooner, for anybody paying attention for the fix. The fuel leak from the injectors were the main culprit, as was the fuel hose that connects the left and right banks. The shop wasn't able to order the hose as a new part, BMW only sells the entire fuel rail assembly and I wasn't going to pay 1300$ for a new rail. They replaced the rubber part with a metal piece so the fuel rail is all metal now. After fixing the fuel leaks, cyl 8 started throwing misfire codes as was cylinder 6. So the shop played around with the coils, reseating them. That did it and the engine runs smoothly. So my recent work fixing the oil leak cost me an extra 1200$ I didn't budget for haha.
	Appreciate 0 Quote