[GeorgeThe4th]

Good morning all, wondering if anyone with the N55 has dealt with a misfire on a warm start. Car starts and idles fine when hot and cold. If there is a delay in time between me last shutting it off while hot and starting it then it will misfire on multiple cylinders when it comes down from its high idle. The missing only lasts for 10 seconds or so before the car heats up again. Even then sometimes I will throw it in gear and it will misfire again but harder since it is under load. Seems to correct itself pretty quick and has not stalled yet. I do not have a CEL or codes. I have replaced plugs and coils recently, hasn’t made a difference. I’m thinking upstream o2 sensor because of the symptoms. My thought is on a cold start it doesn’t do it because it’s running open loop for a longer time and not reading off the semi faulty o2 sensor until it’s warmed up. On a hot restart, it doesn’t because the sensor is still hot. Warm start motor is warm but sensor is cold, car reads off the o2 sensor earlier than cold and gets a false reading and misfires until the exhaust warms it up again. Just my thoughts and would appreciate any insight anyone has. Thank you!

[mwat]

I thought the N55 was notorious for acting weird on warm start at idle for a few seconds.

[Dekero]

I'd say check your fuel injectors for a leaking one...

[FranzX3M]

Was it doing this before you changed the plugs and coils? Could still be a cause. A bad or lazy O2 should trigger a code. Could be carbon deposits or dirty injectors. Try some quality fuel injector cleaner. That will address dirty injectors and combustion chamber but will not address carbon on intake valves which can cause bad idle.

[tastefulX3]

My x3 35i was acting like this too. Did you have any success with fuel injector cleaner? is this something that might require walnut blasting?

[GeorgeThe4th]

I have tried fuel injector cleaner in the past but another bottle of Liqui moly jectron can’t hurt. I think I’m also gonna pull some plugs after letting the car sit and see if I can smell gas on any of them.

[mwat]

I can tell you all that I just changed my plugs and coils, plugs dry as a bone when I took them out leading me to believe there's no issue with the injectors and have no other weird issues and on warm start my car can idle a little funky for the first two seconds. Nothing profound. Once you shift into D it completely stops.

[jkwhar]

Not x3 but came across this thread from google. I have a X5 N55 that has the same issue where I let the car sit for about 10 mins after driving, and the engine would misfire for about 2 seconds at start up and then its fine.

Also, it would randomly misfire when I'm cruising on a highway but this is once rare. I've only noticed it maybe 2 times.

I did get the oil filter housing gasket replaced so I'm wondering if its a boost/vacuum leak from the intake manifold. I wanted to try doing a smoke test but it wont be for awhile when I can get to it.

[solidsnake227]

Originally Posted by GeorgeThe4th

Good morning all, wondering if anyone with the N55 has dealt with a misfire on a warm start. Car starts and idles fine when hot and cold. If there is a delay in time between me last shutting it off while hot and starting it then it will misfire on multiple cylinders when it comes down from its high idle. The missing only lasts for 10 seconds or so before the car heats up again. Even then sometimes I will throw it in gear and it will misfire again but harder since it is under load. Seems to correct itself pretty quick and has not stalled yet. I do not have a CEL or codes. I have replaced plugs and coils recently, hasn’t made a difference. I’m thinking upstream o2 sensor because of the symptoms. My thought is on a cold start it doesn’t do it because it’s running open loop for a longer time and not reading off the semi faulty o2 sensor until it’s warmed up. On a hot restart, it doesn’t because the sensor is still hot. Warm start motor is warm but sensor is cold, car reads off the o2 sensor earlier than cold and gets a false reading and misfires until the exhaust warms it up again. Just my thoughts and would appreciate any insight anyone has. Thank you!

Did you figure it out what is the issue, I have same exact issue on my N55 and I changed new OE injectors, oem plugs, oem coils, valves intake cleaned and all seals replaced , oem vanos solenoids, OEM O2 sensors, OE HPFP, OEM airflow, OEM valve cover, replaced throttle body with a used one, car updated, new adaptation, new engine body power control, used fuel module and programmed to the car, smoke test twice and no leak and I sill have this issue.., any update would help, Thanks

[GeorgeThe4th]

Originally Posted by solidsnake227

Did you figure it out what is the issue, I have same exact issue on my N55 and I changed new OE injectors, oem plugs, oem coils, valves intake cleaned and all seals replaced , oem vanos solenoids, OEM O2 sensors, OE HPFP, OEM airflow, OEM valve cover, replaced throttle body with a used one, car updated, new adaptation, new engine body power control, used fuel module and programmed to the car, smoke test twice and no leak and I sill have this issue.., any update would help, Thanks

I have not found a solution yet. I just replaced spark plugs once again and am afraid didn’t make much of a difference at all. All the them looked bone dry when taking them out and the black stone oil analysis came back with no fuel in the oil. That rules out the injectors. My next step was the o2 sensors but I think I would get a code for it. I would like to do a smoke test if I can get my hands on a machine or through other means of finding an intake leak. This problem is on the back burner for me currently because I am about to replace my control arms to fix a drivability problem and vibration.

[solidsnake227]

I replaced the O2 sensors on mine with OE and didn’t make any difference…. No code is the worse.

I saw some YouTube uses this machine and sounds really good and worked well
https://www.autolinepro.com/products...-smoke-machine


Keep me posted please if you find the problem and best of luck keeping your car healthy!

[Dekero]

My bet is on leaking injectors....

[jkwhar]

Originally Posted by Dekero

My bet is on leaking injectors....

Wouldn't a leaking injector fail the ISTA fuel pressure test plan? I'm almost tempted to buy a BM3 license so I can use the data log for diagnostics lol.

[mwat]

Originally Posted by jkwhar

Not x3 but came across this thread from google. I have a X5 N55 that has the same issue where I let the car sit for about 10 mins after driving, and the engine would misfire for about 2 seconds at start up and then its fine.

Also, it would randomly misfire when I'm cruising on a highway but this is once rare. I've only noticed it maybe 2 times.

I did get the oil filter housing gasket replaced so I'm wondering if its a boost/vacuum leak from the intake manifold. I wanted to try doing a smoke test but it wont be for awhile when I can get to it.

It may not be apples to apples as I believe (depending on the year of your X5) that you have an EWG N55. Not sure if this issue occurs with them or not. Just something to think about.

[Houranimd49]

This has been happening to my 2011 535. But it comes and goes. I’ve isolated it to cylinder 1. I have one new injector in cylinder 1 from maybe 20k miles ago and all the plugs and coils are maybe 40k miles ago.

I also have a 2012 X3 with the N55… same deal. My 2011 135 with the N55 also did it once in a while when I had it. Again, all 3 cars have/had their plugs/coils done in a timely manner.

I think that’s just the way the N55 is. Temperamental. It is what it is. I’ve even heard B58s hiccup here and there. But this doesn’t mean I intent to say there aren’t any underlying issues. It could vary per car. Although in my experience over 4 different cars with all routinely maintained N55s, that’s just how they are (I presume).

[MSport_Jon]

You have a leaky injector. I had this same problem where if I could start the car, t would run smooth and nice and idle nicely as well. When the car was warm and i would go to the mall and come back, I would get misfires as soon as I start the car warm. Replaced injectors and the problem was solved. You can also buy an ultrasonic cleaner and blast your current injectors and see if the problem goes away. That would only cost you an ultrasonic injector plus a few hours of work.

[GeorgeThe4th]

Still to this day doing the same warm start issue, learned to live with it so far. Just scanned the car and had a shadow code 118401 - Mixture control fuel air mixture too lean, large deviation and 11CF30 - Mixture control: multiple fault.
Looked it up and found this video on a failed valve cover that doesn't fail in the typical way by a crack on the outside but rather an internal crack in the vacuum tank portion of the valve cover. In the video it states you can find out if there is a crack/failed valve cover by removing the vacuum line from the valve cover coming from the vacuum pump. If there is oil in there then it has cracked/failed. I am skeptical about this and would like to know what you guys discover. Mine has a good amount of oil when sticking a screwdriver in the tip comes out wet. A while ago I replaced the valve cover gasket and for some dumb reason I didn't replace the valve cover. Hindsight is 20/20 I guess. But I would like to know what you guys find in the way of if it is bone dry or if there is supposed to be some oil in there. Here is the video for reference. Thanks!

[GeorgeThe4th]

Also the car has over 140,000 miles on it and the valve cover has not been replaced to my knowledge so double shame on me