Im paid to sound convinced....


;)


But in all serouslness, on the E39M5 this was an absolute certainty: you did this, You had to.


Also, since those motors run at the edge of AFR control, the maf was hyper critical. bad mafs (ie non-OEM) would hose AFR response


Good luck!

Got home from work just a little early yesterday and with daylight savings time on my side, got the impulse to pull out both VANOS solenoids. It was probably easier than removing a couple of spark plugs. Realized I didn't have any brake or carb cleaner around so very cautiously used my 89 octane cleaning formula (no, kids, don't try that at home!). They actually looked very clean to the naked eye, but nevertheless rinsed, cleaned, and shook on them best I could. Never saw any sludge, metal bits, or other debris, except for all the greasy grit on the outside portions. Took a 6 volt lantern battery and exercised the plungers several times. They both moved, although only a mm or two.

Oiled them up liberally and reinstalled. Cranked up the X and it purred like a kitten. The CEL was not lit for the first time since I don't recall when. Not sure if that's due to me cleaning the VANOS, or if it just coincidentally decided to turn off now, after so many cycles following my replacement of the CATs (I still haven't manually cleared any codes).

Drove it, and it ran beautifully for the first couple of miles. Then, as it warmed up, it increasingly acted "more and more badly", with symptoms hitting their maximum at about 5 or 6 miles, and continuing at about the same level thereafter. This was about the same pattern as before, except that the symptoms I'd say are about 60% improved, and the CEL never came on. Maybe the weather was a factor, IDK.

Thinking to proceed with the A/F sensor replacements, and pull all the spark plugs to see if any are burning differently from the others, or are maybe gunked up with carbon from when the VANOS or CATs were malfunctioning - if they were. Also might consider a way to clean the VANOS more effectively.

A side thought: I also have a very annoying oil leak. It's bad enough that it runs down onto the CATs and makes a very bad smell which really ticks off the wife. I have purchased the valve cover gasket kit and plan to install as soon as I figure out the engine performance issue. Wondering if a break in the valve cover gasket seal could result in a vacuum leak which could cause all this.

OK, updating. The X is still running like crap, particularly after it warms up after 2 or 3 minutes, and especially when you gun it for power after pulling out in traffic, or if going uphill. Sometimes after gunning it, it seems to start missing and running even rougher. I pull over, shut the engine off and restart, and it smooths out some.

So, I've changed out before-CAT O2 sensors, the CATs, the MAF sensor, and removed & cleaned the VANOS solenoids. The CIL has stayed off since cleaning the VANOS, but it still runs bad. I cleared all codes and rechecked. I get a P0305 (Cyl 5 misfire) ("Pending") and a P0420 & P0430 (CAT Bank 1 & CAT Bank 2) (both "Permanent").

The Cyl 5 misfire is weird. I hadn't been getting that until recently, and it doesn't seem to miss at idle, at least not most of the time. Maybe a coil issue. I'll try swapping a couple of coils around to see if the code moves with the coil. (If I remember right, the code doesn't always indicate the correct cylinder, sometimes maybe the one next to it.) Pulled all the plugs, they're not fouled, but all have gaps now of about 0.055 - 0.060. Spec is 0.044, so I got all new ones and will probably install them tonight.

I also have new after-CAT A/F sensors, but haven't installed those yet. Will probably do those this weekend. Was gonna do this past weekend but all my free time went into replacing the valve cover gasket, which was leaking badly. At least that seems fixed.

I've recently learned that these engines have these "DISA" valves in the intake manifold that often cause havoc. I've ordered new ones, along with the Y-configured PCV or whatever kind of vacuum hose it is. Not sure if I'll have to pulll the intake to do any of those, so those will probably be last on my list to try.

Don't know anything else to try, except maybe try doing a better job of cleaning the VANOS. I keep praying though, cause I gotta solve this! Arrrrgh!

One thought- when a car is first started, the DME has it running quite rich.


If, when you start the car it runs great, BUT then as it warms up and the DME dials back the fuel it may indicate it is running lean. (not that the AFRs in the computer will show lean, but 'there's an air leak and the DME doesnt realize it is lean'.)


Are your AFR (aka fuel trims) looking ok?

The saga continues. Replaced all 6 spark plugs last night. Sure fired off briskly, but took it out for a short spin and after a couple of minutes, it ran like the same old crap. Cleared all the codes again and I got P0305 (Cyl 5 misfire) three ways: freeze frame, pending, and permanent. Also got the P0420 & P0430 CAT codes, both of them pending as well as permanent.

I had even swapped the coils on Cyl 1 & 5, but the Cyl 5 misfire code still showed up, with no codes for Cyl 1. I'll try swapping a known good coil with the #4 & #6 coils as well, just in case it's picking up the misfire from a neighboring cylinder and incorrectly reporting it as #5 -- I know it does sometimes happen.

That, and I still have new parts on hand to try swapping out the 2 DISA valves and the PCV(?) vacuum hose. Surely I will get lucky eventually.

I actually haven't hooked up my other reader recently which shows fuel trims. Guess I need to get out all the Blue Tooth adapters, etc., that are involved with it and do that. Right now have just been reading the codes from my cheaper gadget which is simpler and quicker to use but doesn't show all that additional data. Oh, and I have to chase down the app again and reload it on my phone since I'm not sure what happened and it disappeared. Sure it's no big deal but another box to check.

You may be on to something with the DISA valve. When they fail they can let un-metered air in, causing all sort so lean conditions. Search around for 'bad disa' and see if it lines up wiht your symptoms....

Yes I've read several things and watched a few youtubes on it. It makes a lot of sense to me that it could be the culprit, so much so that I just went ahead and ordered the DISAs. I can envision when I really romp on the gas that the valve could be moving or getting sucked around in some sort of an imperfect manner, and then not operating or being intact enough to go back into position until the engine is shut off and restarted. Only thing is most of the stuff I have read/watched talks about the presence of some kind of noise, like a grinding, whistling, rattling, flopping/thump, something, which I'm not hearing. I could see where that wouldn't always be the case, though.

Gonna first try switching out coils 1 & 3 (either side of #5 in firing order) to see if the P0305 moves or goes away, and also install the new A/F sensors. Thanks

OK, officially about to scream! I'd already swapped coils 1 & 5, and the P0305 (cylinder 5 misfire) didn't move. So, swapped coils 1 & 3 about 30 minutes ago, to see if maybe the issue was with either one of those (which are on either side of cylinder 5 in the firing order), but possibly being picked up incorrectly as a cylinder 5 misfire. NOW I'm getting P0301, P0303, AND P0305! :confused::(:mad::banghead:

Clearing all the codes and re-reading doesn't change anything. Reversed the 1 & 3 coils back to where they were before I started this, but I'm still getting P0301, P0303, AND P0305! Crazy!

Wondering if these coils, which are about 8 years old, are so fragile that my handling them once more this evening was just too much?? This is crazy.