[thechao]

2006 325i. The car is idling rough (feels like a misfiring cylinder). When I give the car gas, the skip increases with the RPMs. If I let the car idle for a few minutes, the skip does *not* go away. Here's my theory:

1. MAF would have constant shuddering so it is not that.
2. Leaky injector would burn off after a few minutes.
3. Bummed ignition coil ... or spark plug.

I was thinking of getting a spare ignition coil and doing a swap-out. I had the *exact* same problem a few months ago, and the problem was a bad ignition coil (which the dealer replaced). I want to know if it is likely to get a second bad ignition coil? I am under the impression from PenskeParts/etc. that the ignition coils for my month/year were spectacularly bad & had to be modified several times.

Should I just be prepared to slowly replace every coil as they go bad? What is the possibility the dealer put in a bum coil for the replaced coil?

[325high]

my first ignition coil just went at 60k miles. i have no idea if they're duds and only last about that long but i'm just planning on replacing them as they die. They cost about $40 at getbmwparts.com and they are SIMPLE to install. there's a DIY here somewhere. Anyways, my point is I would just get a couple of coils and try swapping each old one out until you find the dead one. it takes about 20 mins. Worst case is it's not a coil and you'll have some spares lying around for when the do die.

[thechao]

This was my exact thought. ThePartsBin has the OEM part for 34$+5.5$S&H. (If anyone else reads this: there are *two* Bosch parts, labeled by date, get the most recent, i.e., "4/01/2006-" and *not* the "-3/31/2006".)

When messing around with the coils, how clean do I need to be? It looks like most people are using unpowdered latex gloves? My daily is beat-up ol' Contour which runs fine with sawdust in the engine ... so I don't this sort of thing.

Also, I could just unplug the coils serially to figure out which coil is bad, correct? That is, if I unplug the bad coil, the engine will run the same. If I unplug a good coil the engine will run *really* badly?

[325high]

im not sure how that would work but i would just get a new coil before you get cracking. it's a simple DIY but it's a big enough pain that you don't want to dismantle everything just to figure out if that's the problem then have to reassemble and then disassemble again once you have a coil. just get a new coil; it's cheap and you'll need it soon anyway. if you have a new coil, just swap each existing coil with the new coil until the car runs normally. i didnt use gloves or anything. the coil surrounded by rubber so i didn't see any need.

fyi, once you do replace the correct coil, the service engine light might not go off for a couple of days. mine took a while to finally leave me alone.

[thechao]

I just ordered a new coil. Going to put off taking the car to the service center b/c I'm 90% certain it is the coil.

p.s. also going to be changing the brake pads on the front. I couldn't find a sticky DIY for this on the forum ... should I take pictures & post?

[fdriller9]

Is your car throwing codes? You can scan your car and pull the codes.....they should tell you which cylinder is misfiring/bad.

Your local autoparts chain should scan for free.

And there are a couple brake change DIY guides....

[arctic330i]

This just happened to me "cylinder 3 misfire" it was just a bad ignition coil

[thechao]

I ordered an OBDII tool but it won't be in for a few days. I can take the car down to O'Reilly's and use theirs.

@arctic330i: have you had to replace all the coils or just a few?

[325high]

my SA told me the codes don't tell you which coil is burned. they have to figure it out by trial and error. and i'm sure a generic OBDII scanner won't tell you which coil. at the least you'll need a BMW scanner

[fdriller9]

My BT scan tool can tell me which cylinder is misfiring.

http://www.e90post.com/forums/showth...linder+misfire

Looks like some other people have had problems with cylinder 3 as well.

Something I picked up skimming through that thread.....you can swap coil packs, and narrow down the one that is faulty. While you're waiting for the new coil pack to arrive, you can do this and determine the faulty one ahead of time.

Good luck!

[thechao]

Does anyone know a place where I can buy the Bosch part (ignition coil) in Portland, Oregon, that is *not* the dealer. I find it irritating to pay $60+ for a <$35 part.

[mildon77]

Every car built from 1996 and on are OBD 2. Which is a generic system of mandatory coding for emmisions and fuel related systems. If you want to sell your car in the US you must obide by this rule.

Your car will have generic po301 To po306. In order 1 to 6 cylinder numbering. Misfire on that hole. Havent had this issue myself but normally dont want to reuse coil boots because they form aaround the old plug and wont do the same for new plugs. Not sure if you an purchase just the boots. VW eventually had to start warrantying thier ignition coils because of the high failure rate.

Dielectric grease might help a lot of guys droppings cylinders after tune ups.

[thechao]

@mildon77 Okay. Since my OBD2 won't be in for a few days it will probably be quicker to just to play hunt-the-bad-coil than to drive down to a shop which has a scanner. 1/6 chance to find it on the first try!

[Chriztofor]

Originally Posted by auger330

my SA told me the codes don't tell you which coil is burned. they have to figure it out by trial and error. and i'm sure a generic OBDII scanner won't tell you which coil. at the least you'll need a BMW scanner

OR see my sig.

[ninesixtwo]

just replace all of them.

[thechao]

I got my OBDII tool in and the misfire is on cylinder 4. I believe the layout is:

window
6
5
4
3
2
1
bumper

Between 3/4 is a large metal cylinder -- LMC -- (too lazy to figure out what it is). Do I have to remove LMC to get the coil out? Or should I pull harder?

[shibikot]

just replaced all my coils this weekend. I had a #6 one go bad, but decided to get them all changed since my car is about 62K miles old. I had a #1 coil go bad about 2 months before this.

I'd change them all if i were you - its not that expensive, and it takes time to disassemble all the cabin air filter components. Consider changing the spark plugs if they're due soon.

The metal cylinder shouldn't be a problem, i was able to pull the coils out and put them back in without much hassle.

[thechao]

@shibikot Okay. I was hoping to be able to pull #4 without having to disassemble the air filter components. Looks like I'm going to have to do that, then: I simply cannot get the leverage to pull the coil, elsewise. Thanks!

Holy crap. Found txusa03's post on sparks; there was a comment about using a screwdriver+block of wood. Finally got enough leverage to pop the coil out. Of course, in all the excitement I've drained the battery... sigh.

[arctic330i]

Originally Posted by thechao

I ordered an OBDII tool but it won't be in for a few days. I can take the car down to O'Reilly's and use theirs.

@arctic330i: have you had to replace all the coils or just a few?

Sorry for the late reply. They only replaced cylinder 3, I used my OBII Scanner to find out which one it was.

[thechao]

Okay. So lessons learned:
(1) don't try to do a "coil swap" to find out which coil is bad (I'll explain in a bit);
(2) don't constantly try to start the car with a misfire.
Basically, the problem is the car is running both lean (every cylinder but the misfire) and rich (the cylinder with the misfire). The result is that you will effectively flood the engine, making it crank hard/longer. This is bad for a number of reasons; luckily for me, the most immediate "bad reason" is that it drains the battery. Even with a good battery charger the epically-sized BMW batteries take a while to start.

Anyways, after I recharged the car I let it idle for a bit until the engine smoothed out. I'm not sure this is the best way to do this (it sounds pretty rough on the engine). However, once I took it around the block the engine began to purr!

[AlB]

in 5 BMW's never had one, I suspect its the plugs that never get replaced under BMW maintenance program that burn the gap wider which in turn takes more voltage to spark which in turn fails the coil. Moral of the story change your plugs every 30K despite the LIFETIME BS that BMW says

[thechao]

Maybe. The car only has 50K on it, on its original sparks. Even a little research shows that the OEM is on the 4th revision of the coils (about one a year every year since the car was made), so I suspect there is something else (fundamentally) wrong.