# 3 Misfire

[Ziyadh M]

Hi Guys,

I drive a E70 BMW X5 50i N63. So was driving as normal just decided to accelerate a bit, felt a slight hesitation then huge warning in yellow reduced power malfunction and it started missing. Switched of started up again misfire gone. Got home pulled the codes showed # 1&5 combustion cylinder misfire. Cleared errors. Drove the whole day car was fine. Next morning started acting up again. So I pulled codes, now it’s #3 combustion cylinder misfire. Swoped plugs and coil packs around from #3 to #1. Went for a drive goes into limp mode again with misfire. Switch of the on again take a slow drive back home. Pulled the codes and it’s still showing #3 misfire.

So I figure it’s a faulty injector. I got a new coil pack, 8 spark plugs and an injector. Replaced all plugs and in cylinder #3 new injector and coil pack. Coded injector and test drove. Same problem. Pulled codes #3 misfire. Now I’m stumped. Any help please.

[dworthy]

Welcome to the Forum!

Have you tried a leak-down test on that cylinder yet? Also a borescope afterwards wouldn't be a bad idea either.

Next I would look at live data to see what is going on in that cylinder as you accelerate. Is your diagnostic tool capable of doing such?

[asphalt4463]

Weird. I really doubt it in this case but after decades in sw engineering, I have been burned more than once by a misleading, incomplete, or lying error log or message due to an edge case fault. I would check the resistance on the original #3 coil pack and reference against the others including the new one. Look at the results. If the original #3 is out of spec and all the others are in spec, that's a culprit plus something else. Its' a remote possibility that a combination of factors is causing the sw to report #3 when in fact it's not. I doubt it but I've seen weird stuff before. The symptoms sure sound like a coil pack went south.

[Ateyourv8]

You can check by unplugging each coil pack while running and see which one makes little to no difference in idle when unplugged.

[Ziyadh M]

My Tech has a tool that can do live testing. So will get that done and see what happens. I’m crossing fingers that my engine doesn’t have to come out. Thanks

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Just thinking if it could be DME issue reporting #3

[dworthy]

I don't think so, as it has a specific parameters to fall in before it sets the code.

[bmwdirtracer]

Here are a couple of thoughts for you:

1) The electrical plug for the newer style coils must be firmly assisted onto the coil. Gently pushing it on, and letting the lever/clip draw it into place is insufficient.
2) For this complex engine, the only diagnostic computers worth a damn are ISTA and Autologic....and I personally would use ISTA, because it will do a guided test plan.
3) Intake passages perhaps clogged with soot?
4) I don't know whether it exists where you are, but in the US, BMW has a "customer care package" for cars with this engine. It's almost like a recall, in that they do a bunch of work for free . because a bunch of stuff fails. Read this:
http://www.roadandtrack.com/car-cult...ns-bmw-n63-v8/