Ok folks. 2003 BMW 325i.

I'm having TERRIBLE intermittent idling issues. Some days it runs and idles perfectly. Other days it runs like absolute shit when I crank it up. Most of the time if I turn it off and crank it back up, it idles/runs great. WTF. Check engine light has been on for a while now but I cant figure it out and it drives fine most of the time.

Except for yesterday/today. I couldnt make it out of my neighborhood.

It gave me a few codes:

P033 - Misfire detected w/ low fuel
P0300 - Random/Multiple Cylinder misfire
P1343 - System control ignition mis-fire cylinder 1
P1347 - System control ignition mis-fire cylinder 3

Found this thread and this guy had the EXACT same codes and he replaced his coils on the two cylinders and says it's running fine now.
http://forum.e46fanatics.com/showthread.php?t=309147

So I bought/replaced new plugs and it still ran rough. I then pulled each coil pack one at a time and tested with an extra spark plug. Each coil produced spark.

Now it's giving me various cylinder misfire codes each time I clear the codes and let it idle for a bit.

Misfires on cylinders 1, 2 and 3 now.

I'm going to check the fuel pressure in the morning when I rent a fuel gauge from Autozone. I cant find any air leaks (by sound and with the carb cleaner trick).

Some BMW forum threads suggest it might be the Crankcase Valve....I'll be pulling that all apart tomorrow too to check/clean it. 4 hour job.

Anything else you guys think it could be? I replaced the fuel filter 2 months ago, btw.

[Edited on November 30, 2012 at 7:35 PM. Reason : .]

11/30/2012 7:34:10 PM

Coils isn't the same as spark plugs. Buy a new coil (be sure what type of coil/connector your car already has before buying - triangular vs square type) and splurge for the new coil boot as well. I may have a few OEM ones still laying around but most were going bad. One may be good still if you really want it but I'm in CLT right now.

The P033 code should finish the description "w/ low fuel cutoff". The ECM is detecting a misfire condition cutting off the fuel to the cylinder(s) to keep from damaging anything in the converter and wasting unburnt fuel. Go to O'reilly's and repull the codes to verify what you've got as their reader seemed to have the full error descriptions plus a freeze frame of the car's running parameters for each code which can help as well.

Don't do the CCV yet, I did and even though I found the parts relatively cheap online it is a PITA if you've never gotten down near the throttle body or through the DISA valve before and mine was in good condition anyway once I cut open the old one. Get an inspection mirror to verify first; CCV may only be worth it if you can find oil buildup leaking from the actual CCV / dipstick connection or if you find oil/water buildup in the valve cover hose up top. One or all of those 3-4 hoses connecting to the CCV will be brittle and break underneath the manifold no matter how careful you are.

TL;DR
Buy a single coil first to swap out on a misfiring cylinder. Be sure your new spark plugs are the 4 pronged OEM stuff (Bosch or NGK only) and not fouled up; if they aren't that type then you're asking for trouble down the road as the ECM will also slowly derate the engine output if it isn't getting good combustion even without throwing a code. If you haven't already clean the MAF, too. If it's not any of those, especially at idle, then you've got a huge vacuum leak.


[Edited on November 30, 2012 at 10:04 PM. Reason : .]

11/30/2012 9:59:14 PM

Thanks for the reply.

Yes, I realize the coil is not the same as the plugs. I meant that each coil produced spark on the new plugs. I pulled the coils one at a time and put an extra spark plug I bought (yes, I bought 7...1 extra for just this purpose) into the coil and cranked up the car. I then verified I got spark on the PLUG. All 6 coils seemed to be working fine as they all produced spark on the spark plug.

I bought the correct plugs - the 4 prong NGK BKR6EQUP.

I dont think I can drive the car to O'reilly's. I do have a Snap-On Modis diagnostic tool that i'm using to read the codes in OBDII diagnostic mode. It can also produce a freeze frame. I just dont know what the parameters SHOULD be, so I wouldnt know what I was looking at/for really.

11/30/2012 11:03:20 PM

You should probably just Ohm out the coil packs. Best way to know if they are good or not.

I just had to swap out my coils on my 330 because I had 2 coils go bad.

11/30/2012 11:15:33 PM

So to be clear you bought 6 new coils as well or just 6 new plugs? I'd still buy a single new coil w/ boot if it was just plugs or even just a single boot.

^I did the same on my packs, most were I think 0.5 or 0.6 ohms on the primary coil (outer pins) and the two I ended up tossing or replacing were reading 0.4 ohms for cylinders 1 and 2. Only specs I could find on the e46 forums were 0.6 ideally and 0.4 to 0.8 range but I believe those were pulled from e36 data. Might as well check the boot resistance and inspect/clean the plug and coil connections while you've got them out; twist and pop the boot off the coil slowly and be sure they click when putting back together. Just like cracked insulators on spark plugs, the boots can crack and let the arc partially short across the insulation to the spark plug heat shield under certain temps and loads. That wouldn't have shown up during your spark check with the boot far from anything highly conductive.

In lieu of the official specs for the M54 engine I'd do a check of relative resistance readings against all 6 coils/boots instead and see if the bad ones stand out and match up to your cylinder misfire numbers.

[Edited on December 1, 2012 at 12:30 AM. Reason : damnit]

12/1/2012 12:28:27 AM

No, I bought 6 new plugs only, and "tested" the 6 old coils.

I'll pull them and check resistance today to see if I find any outliers. I hate to drop $83/piece for them at the dealership when RockAuto.com has Bosch coils for $25/piece. Might just order 6 new ones from RockAuto and borrow a car for a few days while they're shipped.

12/1/2012 9:03:33 AM

That's where I got mine from, their prices are hard to beat. Keep us (or me I guess) updated on what you find.

12/1/2012 10:33:45 AM

Just tested the fuel pressure. Getting 50-52psi (approx 3.5 bar) at the fuel rail while running...does that seem a little low? I've seen vids online where folks are reading close to 60psi while running...

Next i'm testing resistance on the coils.

[Edited on December 1, 2012 at 2:49 PM. Reason : .]

12/1/2012 2:47:55 PM

All coils read .8 ohms.

Still think it's a possibility it could be a coil?

12/1/2012 3:29:03 PM

Ok, cleared the codes again and now it's giving me P0313 and P01347 (cyl 3 misfire)...so i'm wondering if Cylinder 3 misfires are causing the other cylinders to throw codes too eventually, since Cylinder 3 is the first to show up as having issues...

I'm gonna swap the coil again, clear the code, and run it to see if it changes cylinders.

I also noticed that after I cut the car off, the fuel pressure was still at ~50psi. After about 20 minutes of sitting it had dropped down to 15psi. Is that indicative of a leaky injector?

12/1/2012 3:59:45 PM

Check to make sure the contacts are clean and are not loose. My 2 bad coils had connectors that moved around, and when they moved the it read 1M ohm. When I pressed the contacts down they read .7 ohms.

12/1/2012 5:38:15 PM

What were the boot resistances? I'd still order a spare coil to definitely rule out the coils but doing the swap should help narrow down the diagnostics. If it doesn't change then you've got something that could affect more than a single cylinder such as DISA valve, IAC valve, or MAF. No lean codes yet means it's not an external vacuum issue i.e. CCV, hoses, or intake boots.

I'm not sure you've ever mentioned the miles on it but if it's over 100k the fuel filter should be replaced, mine was chock full of black debris and I could tell it had a smoother acceleration. Be sure to check whether your filter is the regulator type with a vacuum hose or just a standard filter before buying. That fuel pressure seems normal to me, 60psi + would be normal for a e46 M3 I believe. Just to confirm as well, you are using premium gas as well? These M54's can work on regular unleaded but that can exacerbate any minor issues your engine already had.

12/1/2012 8:44:45 PM

When you say to twist and pop the "boot' off the coil, is that the rubber bottom piece that surrounds the ceramic part of the plug? Those just twist off? I tried but it was pretty tight/difficult and I didnt wanna break anything...

It's got 155,000 miles. I replaced the fuel filter 2 months ago when this problem started popping up sporadically.

I currently have the injectors out and am giving them a good cleaning with some carb cleaner. About to button all that back up and see if that changed anything. I'm going to swap the #6 injector with my #1 injector to see if my misfire changes cylinders. That should indicate a bad injector.

12/1/2012 9:13:55 PM

Yeah, thats the boot, basically if you cant spin that part relative to the top coil block then dont try it without a spare handy. I had to break mine loose by spinning it first then i could pop it away. It does feel like you'll break it but i already had a spare used coil and boot from a junkyard just in case. You're on the right track though, do the diagnosis / test on the coil swap before moving on.

12/1/2012 10:58:40 PM

Well, I swapped the coils and it was still telling me I had misfires on cylinder 1 and cylinder 3, so that's why I went ahead and took out the injectors to clean/inspect.

I took out the injectors and sprayed them with carb cleaner and cleaned the outside as they were pretty cruddy, and sprayed carb cleaner in the tops until it dripped through the port of the injectors nice and clear. I cleaned out the crud from the inside of the receptacles(?) with a q-tip and carb cleaner. I lubed up the o-rings with a little motor oil and put it all back together. Basically followed the instructions here for taking everything apart: http://www.bimmerfest.com/forums/showthread.php?t=571302
and these instructions for cleaning: http://www.pelicanparts.com/bmw/techarticles/JF-Tech/BMW_E30_3_Series_fuel_injector_cleaning.htm

Fired it up and it ran great for about 2 minutes then it started misfiring again. The CEL came on, but I dont see any codes yet??? I'll go out again tomorrow morning and run it until it throws a code and can figure out which cylinder is the culprit.

When putting the injectors back in, I reversed the order of them. (put the #1 injector on cylinder 6, #2 on cylinder 5, etc.). I dont remember ever getting codes on cylinders 4,5 or 6...so i'm hoping one of those will throw a code now and indicate a faulty injector.


***Some things I thought might be important*** - It actually runs fine/smooth for the first 30 seconds to 60 seconds or so...then it starts to misfire/sputter. This is pretty much every time I've cranked it today.

I also have the yellow oil light on for the first few seconds after startup...then it goes away. I'm almost 100% positive I have enough oil in there as I topped it up a few days ago. HOWEVER, this has been an issue for the last 2 months. I always figured it was just because I was low just a tad and didnt really worry much about it, but every time I check my oil it's basically completely full. Does this possibly indicate a bad CCV?

[Edited on December 2, 2012 at 12:00 AM. Reason : .]

12/1/2012 11:42:59 PM

Hmmm, not 100% sure on this but the misfiring only after warm-up points to closed loop control. The only thing on the intake side that I can think of to cause faulty sensing is the MAF. I'll have to rest on that one.

The other thing about the yellow oil level light is that if you're sure your oil level is good, then the oil level sensor is bad. They are known to burn out on the e46's and mine did shortly after I got my car. Very easy to swap. The cheapo replacement URO one worked for me but i read that a lot of people had to buy OEM to get their light off.

12/2/2012 12:43:42 AM

One other thing to note - when I clear my codes while the car is running (idling rough), it literally immediately starts running normally again. I know i'm probably not supposed to do that while it's running, but I did it by accident earlier today and noticed that it immediately fixed the rough idling...wtf.

12/2/2012 1:02:26 AM

I've never tried that while running but that re-emphasizes the fuel cutoff to the affected cylinders; by resetting the fault trips you're letting the ECM restart fuel and spark back to them and operate as normal again. When you did that reset did the car idle normal the remainder of while it was running until you shut if off or did the codes come back within a few minutes? Post up the freeze frame data after it throws a code. I'm interested to see the fuel trims and loop status. No problems during acceleration whenever it initially starts and idles fine?

What was the status of the CCV inspection or MAF cleaning?

[Edited on December 2, 2012 at 12:48 PM. Reason : .]

12/2/2012 12:33:46 PM

some junk

12/2/2012 2:18:48 PM

Sighhh. So, I went out today and cranked it up this morning and the bastard idled perfectly for like 10 minutes. So I took it out for a drive since it had been sitting for 4 days only idling.

I drove it up the street to get some gas (was almost empty), and it cranked and idled/ran perfectly all the way home and around my neighborhood. I let it idle for another 10 minutes in my driveway and decided that it was running good enough to attempt to drive to my dad's shop in High Point (70 miles away). I ran out of time basically, as I needed a working car this week. So I left the car with him and brought his car back to Durham. He has a commercial garage and there's a BMW shop up the street that can help him out with specifics if needed.

I did read the codes after I got to High Point and it actually read a few new ones, although I cant remember if I cleared them again after I put the injectors/fuel rail all back together, so these new codes could have been a result of it being the first time it cranked after new injectors installed (starved for fuel, etc.)

P0313
P0300
P1085 - Fuel Control Mixture Lean (Bank 2 Sensor 1)
P1343
P1347
P0174 - Fuel Control Mixture Lean (Bank 2)

So it's looking more like I have an intake leak somewhere. I'll update the thread after he gets a chance to check it out.

Thanks again for all of your help. It's been a busy/stressful couple of days. It sucks when your daily driver is out of commission.

12/2/2012 9:16:12 PM