2011 X6 Misfire
We have a problem x6 from another shop. They put spark plugs in it and replaced one coil before sending it over. We scanned for codes found codes for number one cylinder misfire and random misfire. When monitoring data misfire is mostly on number one cylinder. Swapped injectors and misfire did not follow. Installed vacuum gauge and checked and found engine vacuum within specifications. Checked fuel pressure on scanner and low side with mechanical gauge and it is in spec. Removed spark plug to check valves for carbon build up not able to get clear picture of valves with camera but some carbon can be seen on intake valves. Removed intake, walnut blasted valves and did all the necessary resets after the procedure. Also noted wrong plugs were in the car so we changed them to the bosch plugs should be in it. When the car is cold it is misfires much worse than when it is warmed up. When warmed up it only misfires hard on 1 and 6. Smoke tested and found no vacuum leaks. Thank you in advance for any help!!
We recently had a BMW 3.0 N/A motor come in with a misfire on #6 cylinder, the camshaft was broken between cylinders 5 and 6, so the valves were not opening, great compression and leak down test because the valves were closed. I also had a BMW another time with a broken valve spring.
Out of interest, what year was the BMW with the broken cam? We’ve got a Roll-Royce Phantom coming in with similar symptoms. I know it has poor service history and has definitely missed a number of oil changes...doesn’t bode well :/
Have you scoped current to coils? You should be able to clamp the common supply upstream and display all in parade. If you have a low peak then you can introduce another channel for cylinder identification and move on to checking power / ground for a volt drop etc.
We have not scoped current to the coils yet but that is a good idea.
How are fuel trims looking? What about VVT system? Do a compression test and cylinder leak down test with mechanical gauge or scope. If fuel trims and VVT systems are looking good. I'm not familiar with the VVT on BMW so I can't give you specs.
Fuel trims look fine on the scanner but it does smell lean. Compression and leak down are in spec.
is this misfire only at idle or is it underload as well? if the misfire is at idle only i would look at the valvetronic deviation %. any deveation of 12% or more will cause a misfire. you can rule out if the valvetronic system is your issue you can set the valvetronic set point to maximum lift via scan tool. if the cold start misfire goes away you have narrowed it down the the valvetronic…
It will misfire worse at idle but it still has a pretty decent skip off of idle. The valve tronic system was relearned after the carbon cleaning procedure was done. The scanner wont display fuel trims in % but lambda is staying right around 1. The coils in there do not have a brand on them. The dealer it came from swears they only replaced one coil.
Put BMW plugs in it, Bosch plugs are a known issue. Also have you checked for TSBs?
world pac had bosch listed as oe but ive been burned listening to them before. there really was no change when we replaced the plugs. yes we have checked tsbs and didn't find anything relevant unless we are overlooking something. Is there a specific tsb that comes to mind?
As other has said here set the valvetronic to maximum lift if misfire goes away that is your problem. most likely the intermedía levers are damage on 1 and 6. if all you test were done correctly. Good luck
Buy BMW plugs and install them and go from there. There‘s no point in speculating before then.