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2003 325i m54 automatic. In short, it started with cylinder #5 misfire, has now progressed to #1, #2, and #5 all misfiring together when I start the car.
Stepson took the car uptown a month ago and the main belt tensioner pulley assembly failed(it was squeaking) somehow completely snapped off and disappeared on the road somewhere while he was driving. When that happened, it broke the fan, the fan shroud, the radiator, the power steering pulley, snapped and twisted up both belts, and cracked the tensioner pulley mounts on the oil filter housing.
I went on eBay and ordered all of those parts I mentioned which came new except for the oil filter housing which was used but "working". Installed everything and also replaced the valve cover gasket because the car had a serious oil leak which was causing oil to pool in the plug holes and around coil boots. The coils are all relatively new(the old ones were deteriorated from the oil sitting in there) and I've swapped them around to see if the misfire changes, it stays on 1, 2, and 5. Swapped plugs around and even bought 3 new spark plugs and replaced 1, 2, and 5 with the new plugs, no change still misfiring.
I took the valve cover back off and put everything back together today to recheck my work, the 02 sensor lines are not burned, they're in their proper clip holders and routed the right way, I see 2 grounding straps for the 6 coils that connect via a nut to the posts on the valve cover and they're connected both the first time and reconnected when I checked everything. I checked the breather hoses all connected, electrical connectors for sensors all look connected.
I thought it could be a fuel starvation issue like maybe a plugged injector? The car sat for about a month before I could get all the parts in but I dont have a code for anything injector related. There was a bank 1 or 2 lean "something" code in there before I cleared everything out between doing a recheck of my work but it hasn't resurfaced. On my OBD 2 scanner I did pull up the Live Data setting and it said Fuel SYS 1 OL fault Fuel SYS 2 OL fault but I'm not sure if it was telling me that was a fault or if its just showing it can be a fault as in there'd be a check mark or some type of confirmation "mark" there.
Is it possible the head gasket could be blown? Could that cause these cylinder misfire issues? I don't know if the car ran hot on him when it messed up he says he pulled over when it happened and cut the car off but who knows.. I know these m54 engines can be delicate when it comes to their cooling systems and such, I replaced the water pump/radiator/expansion tank when I bought the car.
The car has had a check engine code for the air intake camshaft position sensor prior to all of this work and it breaking down and still had the code until I cleared everything out, it didn't come back up but I think that sensor could be bad as the car has stalled once or twice in the past but never had a serious misfiring issue like this and I know I should have already replaced it by now.. I know all of this sounds bad but it's my wife's car, she loves it, it has 205k miles on it and I've always kept up with the oil changes and as much maintenance as possible with it over the years. The inside of the valve cover was remarkably clean for a high mileage car when I took it loose to replace the gasket the other day. This car has me totally stumped I don't know what to do with it now though.
 

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the main belt tensioner pulley assembly failed(it was squeaking) somehow completely snapped off and disappeared on the road somewhere while he was driving. When that happened, it broke the fan, the fan shroud, the radiator, the power steering pulley, snapped and twisted up both belts, and cracked the tensioner pulley mounts on the oil filter housing.
Broken tensioner will lead to no working water pump and this caused engine overheat if he continued driving. I think you may have coolant inside the combustions which caused misfire codes.
Do you need to add coolant often?

Do this: drive car to operating temperature, then park it overnight. Next cold morning, remove each spark plug and look careful at the tip for any condensation.
 

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Okay, so your misfires seem unrelated to plugs and coils. You have misfires on both banks 1 & 2.

I would do a compression test on all 6 cylinders just to rule out a bad headgasket or burnt valves. Easy enough to do.
Do it warm if you can, pull all plugs, pull fuel pump fuse or relay, screw in tester and crank engine for 6 revolutions on each cylinder.

As for checking for coolant in cylinders, you can use Sapote's method, but I prefer to swab each cylinder. cut a q-tip in half and tape it securely to a 1 foot section of hose and swish it around each cylinder.
 
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