[TheFSoundguy]

Hello guys! After reading and searching too many post to find a solution. I finally decided to get help! Seems like a wierd issue… sorry in advance for the big text but I want to be clear and not miss anything

First of all, I bought a 535i like 2 month ago (220k km/136k miles). When I bought it the guy told me the plugs had to be replaced. Car was going into limp so I replaced all plugs NGK97506 SILZKBR8D8S (didn’t know until today that they where one step colder), flushed all fluid and car was running great! Until now. Intermitent multiple missfire. Mainly cylinder 3-6. A couple on other cylinders too but from what I saw on ista they are less frequent. Also throw a rich fuel mixture code

So when it begun I just filled my tank. Was completely empty and running with a quarter tank maximum in the last 3-4 weeks. Car started to vibrate gradually within a 2-3km range. It was intermittent but then started to be constant so all this happend really quick. Car went into limp mode. Restarted the car and was still missfiring hard. I was able to get home and run ISTA. I had a multiple missfire with the rich fuel mixture code. First of all I tought I’ve put bad gad in it because I went to a little gas station (maybe a bit of water in tank). I then bought 2 water removed bottle and put them in the tank, went for a 30min ride and car seemed to get a little better. Finally after 15min it was running great.
I ran the fuel grade test on ista just to confirm the gas station haven’t put regular gas. Test was okay

Went to work the next day. Morning ride was good. But when I came back from work it became terrible for a couple of second then came back to normal. It never falled back into limp but had hesitation some some on low acceleration. Its been 3 days and right now car seems to run better BUT sometimes still run wierd and also takes longer to crank. At this point I was thinking maybe injectors was going bad but it looks intermitent and it all begun at the same time so it would be a big coincidence if more than one fail at the same time. Also monitored the rail pressure when turning off the car and pressure seems to stay there. This morning on cold start I had 70missfire on cylinders 6 and not much on other one. In the end of the day no missfire on 6 but 50 on 3. It runs super great without any missfire when at operating temperature! This is wierd.

I just want to precise that I work at literally 1km from my home. Here right now in canada its pretty cold (-10,-20C/-4F) so the car never get to temperature. Doing alot of idle the morning to get a bit of heat. Oil has a strong gas smell too probably from unburnt fuel and cold idle (Oil have 2000km/2month on it).

So I’m pretty confused!

-Could it be the colder plug mixed with all those cold driving? (Carbon build up?)
-Could it be injector 1-2-3-4-5-6? (All cylinder missfiring)
-Could it be HPFP even with a rich mixture condition and good pressure?

I’m really lost and planning doing my oil change sooner and try putting new plugs. If you guys could help me understanding this I would love that

Thank in advance

[TheFSoundguy]

Forgot to precise that I swaped coil pack also! At the moment missfire were staying on their cylinders

[Hoa]

Run a test on the throttle body with ISTA. It sounds like it is not getting enough air.

[TheFSoundguy]

I’ll take a look on this. Didn’t chek the air filter. I’ll try the ista test but I don’t think its an air issue since it starter to go bad real quick and went back to « normal » within a day or 2. It would have been more gradual?

Thanks for your answer if someone else have any idea would be appreciated

[TheFSoundguy]

Anyone?