06 X5 3.0 Code PO302 PO303 PO 305 and PO300 Misfire

[FREE100KSECRET]

Curious, I had first a PO303 code and PO300 which was occasional, put fuel injector cleaner and it seemed to help, but came back, and no same codes on 2.3.4 cylinder, So what would cause this suddenly, checked connections and harnesses, ordered injector when #3 acted up, but I feel it is something else. Any ideas?
Thanks,

[Effduration]

What are those codes? I am not looking them up...

[crystalworks]

Originally Posted by Effduration

What are those codes? I am not looking them up...

No kidding. So frustrating when an op doesn't post the definitions with the codes. Help us help you.

Edit: I see the "misfire" in the title of the post now. Random misfires are usually vacuum leak related as cn90 points out below. Intake bellows is a good place to start but it can be in so many other places. Smoke test would be the best way to diagnose. Otherwise you'll have to start pulling parts for visual inspections. Good luck.

[cn90]

Multiple misfire codes usually point to air leak.

The #1 culprit is the rubber boot feeding the throttle body.
The cracks are usually on the underside, which you can only see once it is removed from the car.

[cn90]

Cracked rubber boot...I posted the photos here...

https://xoutpost.com/bmw-sav-forums/...ml#post1204411

[FREE100KSECRET]

Originally Posted by Effduration

What are those codes? I am not looking them up...

PO300 is misfire code, which obviously can be caused by several reasons, and is a general code at best. The PO302 code in open circuit of injectors, so a bad connection or perhaps bad injector itself.

[FREE100KSECRET]

Originally Posted by cn90

Multiple misfire codes usually point to air leak.

The #1 culprit is the rubber boot feeding the throttle body.
The cracks are usually on the underside, which you can only see once it is removed from the car.

Thanks, agreed, but in my case it started with just #3 misfire and open injector circuit, so I discounted rubber boot as it was not a random misfire, but consistent, so I ordered new injector, but then #2, #4 came up with same codes, PO300 and PO303, 302, 304, so now I don't think all injectors would be open circuit at the same time. So I was curious if anything else could cause problem. I checked boot, no vacuum leaks detected anywhere, so I am stuck. If all cylinders had random misfires, I would agree.

Thanks,

[FREE100KSECRET]

Originally Posted by crystalworks

No kidding. So frustrating when an op doesn't post the definitions with the codes. Help us help you.

Edit: I see the "misfire" in the title of the post now. Random misfires are usually vacuum leak related as cn90 points out below. Intake bellows is a good place to start but it can be in so many other places. Smoke test would be the best way to diagnose. Otherwise you'll have to start pulling parts for visual inspections. Good luck.

Sorry, I just assumed most know most of the codes by heart, so I was wrong, the misfire code is probably the most common of all codes, PO302 open injector code is also common, so I made the mistake of assuming most would know what they are related to, will better define problem rather than codes next time.

Thanks

[crystalworks]

Much appreciated. Most of us here don't go by "P" codes anymore but use the more specific BMW codes that more capable code readers pull out of the modules.

[X5chemist]

An experienced mechanic knows those code by heart.
Did you pull the plug? I've seen individual plugs fail. You can move the coil pack to another location or ohm it with a voltmeter. Compare ohm reading between coil packs. You can do the same for fuel injectors. One cylinder miss fire will cause other cylinders to misfire even though other cylinders may be okay. The P0303 is where I would look the most for troubleshooting. MAF and air intake leaks are very common causes.