Pulled Codes After X5 Started Misfiring - Confusion Ensues...

[Bayerische E53]

Yes, I've read about the vacuum problems. As soon as I have a chance I will start there. Being that the vacuum and CCV stuff is the easiest to do, I'll do that first. I'll probably clean the MAF and check the DISA/ICV just in case (but there are no codes showing faults with those units so those will be the last I do). If that doesn't work, I'll have to try the pre-cat 02 sensors. What a pain.

[sockethead]

Originally Posted by Bayerische E53

Yes, I've read about the vacuum problems. As soon as I have a chance I will start there. Being that the vacuum and CCV stuff is the easiest to do, I'll do that first. I'll probably clean the MAF and check the DISA/ICV just in case (but there are no codes showing faults with those units so those will be the last I do). If that doesn't work, I'll have to try the pre-cat 02 sensors. What a pain.

Defective DISA shouldn't give you the codes you are seeing. The DISA merely changes plenum/runner volume at around 4000 RPMs. That being said, they do fail and when they do, parts can enter the intake and travel down into the engine.

Here is some good reading on the DISA issue and when the time comes, I strongly recomend this kit. It cured a stumble I had at around 4000RPMs in my e46 even though the DISA didn't appear to be defective.
DISA Valve Repair Kit

[Bayerische E53]

Originally Posted by sockethead

Defective DISA shouldn't give you the codes you are seeing. The DISA merely changes plenum/runner volume at around 4000 RPMs. That being said, they do fail and when they do, parts can enter the intake and travel down into the engine.

Here is some good reading on the DISA issue and when the time comes, I strongly recomend this kit. It cured a stumble I had at around 4000RPMs in my e46 even though the DISA didn't appear to be defective.
DISA Valve Repair Kit

Thanks for that post - pretty cool. I'll look into that in the future when the DISA does need replacing.

Any idea what the codes, then, may be? I'm starting to think that if it's not any of the vacuum stuff, it must be the pre-cat 02 sensors. But the thing that keeps throwing me off are the misfires - and the fact that only one cylinder isn't misfiring. If both 02 sensors are causing misifiring, wouldn't ALL cylinders, as opposed to just 5, be misfiring? And what about the fact that the GT1 only showed two cylinders misfiring as opposed to the 5 my Peake Tool is showing?

I'm not amused.

[sockethead]

I'd still check everything else before changing the O2 sensors. I've seen too many e46s where the O2 sensor code was caused by something else BUT if you have over 100K on the car then you should change the pre cat O2 sensors anyway per BMW maintenance schedule...

[bastereo]

Oh my goodness guys!

You have codes for control limit reached (the GT1 I would think could tell you lean or rich)
More likely lean, and soo lean its causing misfires.
And not setting a code for #6 by random chance. To explain: the DME has a threshold for how severe a misfire needs to be to set a code, so the other cylinder are missing bad enough to reach that, #6 is not. (would be a very slight difference) None of the cylinders would be complete and total misses at this point.

You have an intake/vacuum leak, search here for the common ones and check them out. (I should mention that on these cars a failing maf will act the same as a vacuum leak and not set a code for the maf)

Also, the DISA valve often fails, always in ways that it does not set a code for itself. But they are on my common vacuum leak list.

[Bayerische E53]

Originally Posted by sockethead

I'd still check everything else before changing the O2 sensors. I've seen too many e46s where the O2 sensor code was caused by something else BUT if you have over 100K on the car then you should change the pre cat O2 sensors anyway per BMW maintenance schedule...

Car has over 150,000 miles - maybe I should do this anyways. Thanks for that.

Originally Posted by bastereo

Oh my goodness guys!

You have codes for control limit reached (the GT1 I would think could tell you lean or rich)
More likely lean, and soo lean its causing misfires.
And not setting a code for #6 by random chance. To explain: the DME has a threshold for how severe a misfire needs to be to set a code, so the other cylinder are missing bad enough to reach that, #6 is not. (would be a very slight difference) None of the cylinders would be complete and total misses at this point.

You have an intake/vacuum leak, search here for the common ones and check them out. (I should mention that on these cars a failing maf will act the same as a vacuum leak and not set a code for the maf)

Also, the DISA valve often fails, always in ways that it does not set a code for itself. But they are on my common vacuum leak list.

Thanks for the informative post. As I said, yes, I'll be checking for leaks first. If I don't find one, I'll check the MAF and the DISA.

It's interesting that a failing MAF/DISA won't always trigger a code. That's annoying.

I'll let you guys know how I get on...

[bastereo]

The computer is dumb, you have to be smarter.

Sent from my SGH-i917 using Board Express

[Bayerische E53]

Hi guys,

Just a quick update with a potentially obvious discovery. The car started nearly stalling on me again so I had enough - I started poking about. Here's what I've found/done:

1. First I did a quick check of the CCV system. A cursory check of the CCV system (I removed the engine covers and intake scoop for better visuals) revealed no obvious cracks but it's impossible to tell without a smoke test. Not being able to perform a smoke test, I moved on to the next bit.

2. I figured I'd check the DISA valve. Got it removed and, low and behold, the flap was completely torn from the pulley. Not having a spare, I just took the flap off and reinstalled the body to seal the manifold. Obviously, that didn't help anything. I'm still throwing the same codes so this doesn't really tell me anything at all. I'm going to need to get a new one. Regardless, I'm betting that a failed DISA doesn't really have anything to do with a nearly stalling engine. Sure, you'll lose low-end torque, but I don't think your engine would suffer just to stay at idle. If someone knows otherwise, please let me know.

3. I checked the MAF. I did the tap test when the engine was not misfiring and the engine did not stutter so I think it's good. When I unplug the MAF, the engine does stutter and when I plug it back in the engine stutters again, leading me to believe that all is well with the MAF. Can anyone confirm?

4. Here's the "fail" moment. I figured I'd do one last and probably time-wasting check: the air filter. "It couldn't possibly be a dirty air filter," I thought. HOLY HELL. When I pulled it out a bunch of dust just fell out. Not having a replacement, I just gently hit it against my outside wall to let as much of the dirt come out. Jesus, it was like a dust storm. When I put it back in and sealed the airbox, the engine actually started running better and HAS NOT thrown any codes since. That said, the engine still does not run perfectly. Although it doesn't idle nearly as rough as before, there is a very faint feeling that the combustion process is missing a bit (the engine is almost, but not quite, as smooth as my other M54 cars). I'm hoping that the air filter is so damn clogged that it's still causing a mildly rough idle. I'll try to replace the filter and see what happens. I hope it's not something more serious like an 02 sensor or vacuum issue.

In case you guys were wondering, I have no idea when the filter was last changed. This is not my car (family car) so I have no clue. I started maintaining this car when it had just under 90,000 miles and it now has just under 150,000 miles - I just realized today that I haven't changed the filter since I've started maintaining it and god only knows the last time the filter was changed. That said, the filter easily has at least 60,000 miles on it. Now, I have taken it to the dealer on a number of occasions, but I don't think we've done any maintenance (it went for a faulty compressor a couple of times - that's it - and I doubt they changed the filter).

I feel like enough of an idiot for not changing the filter - I do all my damn oil and oil filter changes, all my pad and rotors changes, all my fluid flushes, and somehow I forgot the AIR FILTER? For Christ's sake! I'm going to replace this thing on Monday. If this causes the misfiring to completely go away, I'm REALLY going to feel stupid.

Is "Whoops?" a good enough excuse?

As you can see in the OP, I've been consistently getting 02 trim and misfire codes - would a really dirty filter cause the engine to run lean/rich and misfire? If the MAF is working properly, I would assume not as it still registers how much air is going through the system and that therefore it would have to be a vacuum leak, ignition coils, or O2 sensors - but maybe I'm wrong?

One more test I'm going to do is the following - the next time she starts misfiring like crazy, I'm going to unplug the electrical connector from the DISA and see if that changes anything.

[Bayerische E53]

I fixed the problem. It was none of the fears I mentioned above; it was the damn DISA valve.

I ordered the G.A.S. DISA repair kit and installed it - haven't thrown ANY CODES AT ALL. Well, here's what happened - my DISA flap LEVER broke in half. What I didn't realize was that the lever is hollow (has a hole running through it from outside the manifold to inside the flap. Well, this means that when you remove the DISA flap, the lever effectively becomes a hole on the side of the intake manifold (i.e. a vacuum leak). It was this that was throwing all the codes in my car; the DISA itself was the vacuum leak that I was trying to chase around.

Problem solved. So, the next time one of you have any sort of lean/rich, misfire, or 02 sensor codes and a rough idle, check your DISA valve first; especially because it's the quickest and easiest thing to check. If the DISA is broken, it's more than likely the reason your car is throwing those codes.

I am so impressed with the build quality and obvious durability of the G.A.S. kit that I'm ordering two more kits; one for each of my other M54 cars. Brilliant.

[sockethead]

Good detective work! who would of thought...
That air filter... LOL

Yea the GAS part is a work of art isn't it?