Random misfire when battery low

Ron550 · 02-10-2023, 02:27 AM

Getting random misfires on 3 cylinders on my n63 550i. Replaced coils and plugs already. Noticed that if I put the car on a charger for a few hours it would run fine for 1 to 2 starts. Battery and alternator have also been replaced since. No difference. Any idea what could cause such an intermittent misfire? Very bad misfire btw car shakes like crazy and puts me in limp mode. And maybe charging the battery has nothing to do with it and the car only runs better cause it was sitting for a few hours.

EL Jeffe 5 · 02-10-2023, 07:15 PM

I will try to help you but I need your help as well 🤣
I will go first how many miles do you have in the car have you done your valve seals is your car smoking.
I know before I did my valve seal my car was running rough.
Two it can be your fuel injectors.
If you have ista+ you can check performance if each file injector.
Three check your PCV valves on both sides make sure there not cracked.
That can cause roug running.
If I was gonna make guess I would have to say fuel injector.
You can check this but taking one spark plug at time and try to smell for fuel.
If you can smell fuel on that cylinder. You have confirmed your issue.

Now can you do me a favor since you have 550. I have 550 I’m concerned about negative pressure in my engine.
Can you start your can and open your oil fill cap and see how much pressure is being sucked back in engine. That’s called negative pressure. I guess it’s okay to have some but in my 550i it’s hard to take off cap when engine is running I just need confirm from other 550 just to make sure it’s okay.
Thanks

Ron550 · 02-11-2023, 08:33 PM

130k miles on the car and my car does smoke and smell like oil a little bit but valve seals were replaced under warranty about 70k miles back. If it was fuel injectors would it be so intermittent and would I be getting 3-4 misfires at the same time?

And about the oil fill cap I do have a ton of negative pressure and I was very concerned as well when I noticed it a while back but even when my car decides to run fine and not misfire there's still quite a bit of negative pressure so I wouldn't be too concerned. Just replaced the PCV valves on my car too cuz I thought that was causing my misfire.

Thank you for the suggestions.

02-10-2023, 02:27 AM	#1
Ron550 Registered 0 Rep 2 Posts Drives: 2011 BMW 550i Join Date: Feb 2023 Location: Los Angeles iTrader: (0)	Random misfire when battery low Getting random misfires on 3 cylinders on my n63 550i. Replaced coils and plugs already. Noticed that if I put the car on a charger for a few hours it would run fine for 1 to 2 starts. Battery and alternator have also been replaced since. No difference. Any idea what could cause such an intermittent misfire? Very bad misfire btw car shakes like crazy and puts me in limp mode. And maybe charging the battery has nothing to do with it and the car only runs better cause it was sitting for a few hours.
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02-10-2023, 07:15 PM	#2
EL Jeffe 5 Major 612 Rep 1,254 Posts Drives: CBR1000RR Join Date: Aug 2015 Location: Iowa iTrader: (0)	I will try to help you but I need your help as well 🤣 I will go first how many miles do you have in the car have you done your valve seals is your car smoking. I know before I did my valve seal my car was running rough. Two it can be your fuel injectors. If you have ista+ you can check performance if each file injector. Three check your PCV valves on both sides make sure there not cracked. That can cause roug running. If I was gonna make guess I would have to say fuel injector. You can check this but taking one spark plug at time and try to smell for fuel. If you can smell fuel on that cylinder. You have confirmed your issue. Now can you do me a favor since you have 550. I have 550 I’m concerned about negative pressure in my engine. Can you start your can and open your oil fill cap and see how much pressure is being sucked back in engine. That’s called negative pressure. I guess it’s okay to have some but in my 550i it’s hard to take off cap when engine is running I just need confirm from other 550 just to make sure it’s okay. Thanks __________________
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02-11-2023, 08:33 PM	#3
Ron550 Registered 0 Rep 2 Posts Drives: 2011 BMW 550i Join Date: Feb 2023 Location: Los Angeles iTrader: (0)	130k miles on the car and my car does smoke and smell like oil a little bit but valve seals were replaced under warranty about 70k miles back. If it was fuel injectors would it be so intermittent and would I be getting 3-4 misfires at the same time? And about the oil fill cap I do have a ton of negative pressure and I was very concerned as well when I noticed it a while back but even when my car decides to run fine and not misfire there's still quite a bit of negative pressure so I wouldn't be too concerned. Just replaced the PCV valves on my car too cuz I thought that was causing my misfire. Thank you for the suggestions.
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