I get it. The "Ignition off then on immediately solves the problem" symptom means nothing. I understood this after your original replies. In hindsight, I should've gone back and edited my posts to remove this.

I agree. After reviewing the fuel trim data again, it does not seem to be all that bad. Sure, I could work to get the long term value on Bank 1 closer to 0, but +5.5 should be just fine and not throw any codes.

Through an unfortunate turn of events last night, I may have stumbled upon the cause of this: Leaving work, I get into my X5 and turn the key. Dash lights up momentarily then all goes dark. No click of the starter, no dash lights, no 12V, nothing except a faint airbag light and the light from the LED on my cigarette plug phone charger. Key won't even unlock doors remotely. After initially fearing the worse, I calm down enough to think through it and come to the conclusion that I either blew a main fusible link or there is something wrong with the battery connections. I've seen this behavior before on severely corroded battery terminals. Worst case I had a catastrophic failure with my battery. I get the last employee left at work to give me a jump through the engine compartment so I can open the rear hatch. Upon inspecting the fusible links I notice that the positive cable is loose. Tighten it down and, voila, all is good. I purchased this car in December and, although I have disconnected the negative cable to replace the stereo, I never had a need to check the positive. On my way home I begin to wonder if this could be the cause of the misfire so I let it idle in my garage for almost 2 hours. No SES. Cold start this morning and idle for 20 min. No SES. Its only been 1 day, but the misfire's came on quicker than this before. I will monitor for a week and post back on this site if this fixes it.

Well, after only one day the misfires are back. So much for an easy fix.

Same as before, SES came on while driving, but computer didn't turn off the injector until car was at idle at a stop light. I'm assuming this is happening because all the misfires are happening at low RPM's. My X5 is a manual transmission so this seems plausible.

I'll be doing cylinder compression tests, fuel system pressure tests, and checking for possible intermittent vacuum leaks this weekend as well as reading live data with BMW laptop software.

Really don't want to go through the "replace and wait" method of repair without knowing more so any additional advice would be helpful.

I would remove the DISA valve and inspect the flap.

Upallnight,

Thanks for the quick response. I already did this and, although the valve looked absolutely fine to me, I ended up rebuilding it anyway with the kit from German Auto Solutions.

So I finally got around to getting some live data with INPA. The first pic below shows the 'Rough" screen which, from how I understand it, gives an indication of how much adjustment is needed per cylinder, in idle, to compensate for a 'rough running' condition. Lower numbers are better. In my case, it seems that cylinders 2, 3, 5, and 6 are running rough while cylinders 1 and 4 have an acceptably low value. You can actually see cylinders 5 and 6 in the below pic crossing over the red line which, I assume, is the misfire condition. I have been consistently getting cylinder 2, 5, and 6 misfires with 5 and 6 the most common.

The next pic is of the O2 sensors page. Unless I'm reading this screen wrong, both pre and post cat O2 sensors show full heating and this doesn't change after the engine warms up, which seems odd to me.

The final 4 pics show the analog values of various sensors. The first 2 pics are at idle and the last 2 are at around 3700 RPM. I posted the pics at 3700 RPM because that's when "ignition timing" seems to have an issue. You can see it at full value (33 degrees advanced) and with the 'exclamation point" in the 5th pic below.

So, a couple of more clues came from the INPA data:

1. Rough running of cylinders 2, 3, 5, and 6
2. All four oxygen sensors are at max heating when engine is cold and warm.
3. Ignition timing goes out of spec at higher RPM's

The ignition timing I would peg to a failing camshaft or crankshaft sensor, but the O2 sensor data is throwing me. Again, any insight into this issue would be greatly appreciated!

After some more research after I posted my last post with pictures, I am heavily leaning towards bad upstream O2 sensors.

I think the max heating is correct for the sensors because the screen grab I posted above was taken at idle and there probably wasn't enough exhaust flow to keep the sensors at operating temperature.

However, both downstream sensors are indicating a highly lean mixture while both upstream sensors are indicating a highly rich mixture. From my understanding, this is basically impossible. If the upstreams are rich, the downstreams should also be rich, albeit by a slightly smaller amount, therefore, either the upstreams or the downstreams are giving false information.

My thinking is that the upstreams are toast and are sluggish. They're constantly giving a rich signal which is causing the ECM to go lean and, in turn, causing the random misfires and rough running cylinders.

Can anyone confirm my analysis?

In case anyone is interested, I finally found the issue. After checking into every possible system in the vehicle, it ended up being the first thing I thought of and the last thing I wanted to fix: the head gasket.

Actually, the issue was related to both the head gasket and the fuel filter. I was getting codes for multiple misfires on cylinders 2, 5, and 6. Cylinder 2 was much less frequent than 5 and 6. During a fuel pressure test, I noticed that the fuel pressure was quite jittery while the engine was running. After finding out that the fuel pressure regulator was integral to the fuel filter, I replaced the fuel filter. During replacement, I noticed that the vacuum hose at the fuel filter was completely shot and the fitting was corroded. Tracing this back, the hose in the engine compartment that goes into the intake manifold boot was also shot. Replacing the hose and the filter took care of the misfire on cylinder #2 but not cylinders 5 & 6.

On to a compression test and leak-down test which gave a strong indication of a a head gasket leak between cylinders 5 and 6. After kicking myself for buying this car, I took the plunge 2 weeks ago. Pulled head and, sure enough, head gasket showed a channel between 5 and 6. Reconditioned the head, replaced some other things while it was out, and put it all back together. Been 2 weeks now and no misfires. "Rough" page of INPA shows all cylinders normal. On to other, less challenging, issues.

Thanks for the follow-up with the solution.

Having two problems at the same time always makes debugging tougher.

Fuel regulator aside, knowing what you know now, if you had another car with the same symptoms, how would your debugging sequence be different? How early would you go to the compression and leakdown tests?

Always go with your gut....

I really didn't want to tear the engine apart of a car I just bought no matter how much I liked the car. That's what made me look everywhere else except compression.

I'm not sure if I would do anything different if I could do it over again. Typically, a misfire doesn't come from a blown head gasket. It can, but there are usually other symptoms involved. I.e., loss of coolent, blue smoke, oil in coolent, rough running at all RPM's, etc. So, this one had me stumped. With that said, had I performed the compression test right away, I would have known something was wrong in the cylinder and not gone through the trouble of other tests.

A decent PPI with a compression and leak down would have pointed out a problem at the very beginning. Who know, if you like the car still you could have brought this to the attention of the seller and could have gotten the car for a lot less. With modern day car it's best to be knowledgeable about inspecting used cars prior to purchasing. I always carry a bluetooth scanner with me when I inspect a used car. If the readiness is not complete, I know that the seller had recently reset the trouble code. I normally walk after this.