I once had a total PITA with TWO bad coils...nothing made sense. However if you are having running issues/misfires due to air leaks or other 'global' problems (ie not cylinder specific) it can manifest as a few misfire codes. I think based on how the DME decides where it is in the firing order it can look like a fixed pattern...

All this has totally messed with my motivation. Was gonna tackle at least one of the DISAs this morning. Now I'm not so sure I should yet. It definitely idles and runs like it has multiple misfires now. I installed these coils in December 2015 following another totally confusing and mystifying episode of multiple codes and misfires. Studying fuel trims didn't seem to clarify much for me at the time, but I did speak with the local BMW service manager then, and he put the bug in my ear to just replace all the coils. I did, and it purred like a kitten. I know, I'm throwing parts at this thing, but I'm gonna go ahead and replace these 8+ year old coils. Seems like it couldn't be a bad thing since the originals only lasted 6 years anyway. I'll go ahead with the new A/F sensors but will wait until I've tried the new coils before tearing into the DISAs.

Installed six brand new Bosch coils last night. It sure smoothed out the idle, with a very steady and smooth exhaust stream coming out the tailpipe. No evidence of a misfire at all now, except that it still gives me the P0301, P0303, and P0305 codes, as well as the P0420 & P0430. Took it down the road and it did fine until it warmed up after a couple of minutes, and then it started "lurching" and chugging whenever you put the pedal down for power or go uphill, same as before. Maybe not as bad though. The CEL had come back on and stayed on after I swapped the 1 & 3 coils a few days ago, but now with the new coils it is off.

Guess I'm back on track now to move forward with changing out the after-CAT sensors, then ripping into the DISAs. I think changing the coils was a good thing to do, given their propensity for failure on these models. Seems like a weird thing that they decided to go south just now in the middle of all this, though. Go figure.

I dont think the coils were totally bad.


I think you have unmetered air coming in- as discussed above, when the motor is running rich during cold start, the 'rich running' and 'lean due to air leak', balance out and it is fine. Once it warms up and the DME tries to run closed loop, it is too lean and you get rough running and misfires.


Something I have seen before- an apparent 'pattern' in misfires, atrributable to specific cylinders, where you would expect a 'global' issue to cause misfires on all cylinders. I believe this may be due to how a DME 'senses' a misfire... the DME only sees crankshaft position..a steady stram of tic tic tic coming in. When it seems a tic tic ....tic (in other words a slight pause or more accurately not the expected acceleration of the crank due to a firing) it says 'misfire. I belive the DME may use a single 'pin' on the crnk to reset with each revolution, so when you see 'its always 1 and 5' it may be in fact due to the algorithm for detecting a misfire. My pet theory.


Good luck man!

I can totally buy that. Still, incredibly weird I was only getting a misfire on 5, until I swapped the 1 & 3 coils and then got "misfires" on 1, 3, and 5. Then, swapped the 1 & 3 back and continued to get misfires on 1, 3, and 5. And even more so when going with all new coils and continuing to get misfires on 1, 3, and 5. I could understand a DISA issue or vacuum leak generating all those codes. But why now, and not before I swapped up the 1 & 3 coils?? Makes no dang sense.

Finally replaced the after-CAT A/F sensors last night. Looks a little cleaner, since the old ones were drenched in oil from the now-repaired valve cover leak. However, it didn't change a darned thing with the way it runs. It's on to the DISAs and maybe the PCV hose now. Lots of new parts have been installed. Maintenance, right?

I do have 3 oh-by-the-ways, a couple of them which I'm thinking may have some remote chance of affecting the way this thing is running:

#1 is my 7+ yr old, battery. Voltage checks good (~12.3 V w/ car off) but we are starting to get more & more notices of "Low Battery". Might get it checked for capacity, or just replace it, at this age. I have known of BMWs doing really weird things with weak and/or aging batteries.

#2 is a modest whistling/whining noise sometimes when I first start the vehicle. Goes away after a minute or so. Almost sounds like a rusty pulley bearing or slipping belt but a video I saw made me realize it's more likely some sort of vacuum or PCV related thing. I get the same sound by removing the oil filler cap while the engine is running. And, we've talked about vacuum leaks, right?

#3 is that I have an annoying slow coolant leak. I'll replace maybe a pint in the reservoir anytime after the wife goes on a day trip around town. Have not seen any clear signs of where the coolant is going. I did however see a video pointing out that a seal or gasket under the oil filter housing is commonly the culprit. Not sure if there is anything vacuum related with that seal. I can see a good bit of crud caked up under the filter housing, possibly from a chronic slow coolant leak.

#1- almost surely no relation to the issues. 7 years in heat is about it. Might get thru summer, then when temps drop it will die. But if you are getting battery low warnings, likely sooner


#2. Yes. sucking air in can be the issue. HOWEVER, does your car have a secondary air pump? Sounds like a rusty hair drier on cold starts.


3# - Doubtful. Still annoying tho. Assume your oil looks fine, no brown crud/foam?!?

Did replace the battery this past weekend. It was 7 years & a month in the vehicle, about 8 years old from the manufacture date. Had the store bench check it anyway, and it was good but at about 60% capacity. It was time for a new one, no matter, but it hasn't fixed the way the car is running. Chasing vacuum leaks and DISAs, etc., will have to wait for a couple of weeks b/c I'm getting ready to leave on a cruise out of Port Canaveral, down to San Juan, PR. Pina Colada, here I come!

Cheers, mate.



Ive got a few weeks in Hawaii coming up....


:thumbup:


:plane:



:dancing: