Multiple Misfires!!!!!
 

I have a 2003 BMW X5 that is giving me multiple misfire codes (P0201, P0363, P1343, P1345, P1353, P1357, P1355, P1349). After sitting overnight, I can start the car and drive 30min to work without any codes or CEL. When I get in to go home, the CEL will flash, engine power will be reduced, and will come and go intermittently. Upon pulling the codes I will get any variation of the multiple cylinder misfires. I've changed the crankcase vent valve (CCV), intake manifold cover vent valve, sprayed carb cleaner looking for changes in idle, and changed both valve cover gaskets. I do get oil on a couple spark plug wells on both sides which is why I changed the gaskets. I've checked for pressure when removing the oil filler cap and there is none. I'm down to changing spark plugs and then the fuel filter. Other than that I'm am scratching my head and tired of throwing parts at this. Do any of you have any insight into what else to check for or how to check the fuel filter before I spend money changing it? :dunno:

You can check the fuel pressure at the fuel rail and if it not up to spec., the next thing to check will be the fuel filter and finally the fuel pump. But you will need to have a fuel pressure gauge and know how to tap into the fuel rail.

No such thing as a cheap fix for a BM Trouble U.

Do you have a 3.0 or a 4.4?

Could be a coil if the plugs are not the remedy...

What is your mileage?

I think he has a V8 since he changed the valve cover gaskets on BOTH sides. Not unless someone threw in a V6.

Yes, he did say that, did not read in depth enough...

Check if you have oil leaks, you did valve cover gasket both bank and all O ring changed i presume Check also your cam sensors ...you have 4 on the V8 ..those will generates misfire if you have leaks (creating some ground bad contact) ...although you would get a code for them..i would put fresh plug also.

Ps add your X model, engine in ur signature ...

coils?

If you didn't change the plugs when you had a bad VCG, I would replace those first. Then check the fuel filter/pressure. Having failed that, coils.

I changed my plugs at 92k and it started throwing codes around to different cylinders. Replaced the coil it said was misfiring but it didn't solve it. Jumped to another cylinder, including both banks.

Replaced all the coils and 10k miles later, still good.

You will get a lot of different answers but all good advise, especially if its never been done or is unknown to you.

I went with the cheap URO coils $32/each for trouble shooting purposes. Since it seems to have solved it, looking at replacing with Bosch brand when the issue comes back.