[raj55]

My E91 320i from 2009, with a N43 engine started to have low rpm stutter (at 1500 to 2000rpm) during load and acceleration which got worse as the engine warmed up. The dealer on hooking up the code reader diagnosed it as fault in the cylinder number three and changed spark plug, coil, and injector on that cylinder and charged a hefty sum. The car has only done 50000 Km, yes a low milage car. BMW quality??? That did not completely cure it since the stutter was back after one day. Called the dealer again and he wanted to do another diagnostic and repair (for another hefty sum I guess!), but he had no time for at least three weeks, he said. So what does one do? Started to google for ideas and came across this thread and it convinced me I had the same problem.
https://www.bimmerforums.com/forum/s...eleration-323i

But my car did not have a replaceable coil boot but the whole coil had to be changed instead. So searched for a you tube video on how to replace coils in N43 engine and came across this.

Bought three coils and got going, using the video to guide me. Took out the coils from cylinder 1, 2, and four and replaced them with NGK coils and the engine is running smoothly without stutter at all speeds. Wow!
Now comes the interesting part, on close inspection the rubber like covering (boot?) on the coil number 2 and 4 show a burnt black mark at exactly the same spot on both coils. See the picture. Coil number one has no burnt marks. This has been described as the arcing ignition coil.
Skimming through the internet, the cylinders in number 2 and 3 have the most problem. So what is going on here? Is it the heat that is causing our coils to fail because these engines like to run quite hot compared to other cars. Cylinder number one runs cool since it is closest to fan in front of it, the last cylinder (4) has also a free wall to dissipate heat but the 2 and 3 are the worst off. I know they are water cooled but perhaps there is a temp difference after all between cylinders. Or are the coils by Bosch and others of bad quality? There have been multiple superseding coil designs since then in these cars. Better insulation of the succeeding coils? Yet another reason for the problem may have been the way BMW engineers have angled the spark plug tunnel since the long axis of the spark plug and the long axis of the tunnel in the engine block do not align (needing a special hinged key to remove spark plugs), leading to one side of the coil pressing more against the engine block in that tunnel and there by leading to heating and arcing. Another example of bad design. What ever the reason the engine is eating up coils almost every 30000 to 40000 Km. The Japanese car manufacturers would not have released the engines with such faults in them and certainly not without extensive testing. I did not change the spark plug this time since I wanted to know where the specific problem was.

The dealer had actually changed the spark plug and coils in this car after 3 years of guarantee time had expired in 2014 (for a hefty sum) some years back. It had no symptoms of stutter then but I believe there was an indication from the manufacturer that there was a problem with these engines and their ignition,( but why charge me money for that change then!). BMW is not taking responsibility for their cars and their bad design and poor components. For me this is the last BMW.

[Phil325i]

The fault you've found may be why the latest version of the BMW OE coils (made by Delphi) now have a metal heat shroud wrapped around the outside of the coil...

http://www.e90post.com/forums/showthread.php?t=927664

[Dormermike]

I've had a similar fault with Delphi metal shrouded coils bought from ECP. A black zap mark right through the plastic bit making a connection back to the metal shroud.

[Phil325i]

Originally Posted by Dormermike

I've had a similar fault with Delphi metal shrouded coils bought from ECP. A black zap mark right through the plastic bit making a connection back to the metal shroud.

Oh dear - so looks like the re-design didn't work...

[Dormermike]

I'd say not unless it was a dud. I bought three and the other two are working. I don't hold much hope for the index 11 injectors being all that long lived either...

Was speaking to a BMW service manager who seemed to think the n53 had timing chain problems during 2012 and 13 too. Mine is 2012. Not heard of anthing on forums though.

[IanS100]

There was a time, before manufactures started adding one coil per cylinder, that a coil was expected to last the life of a car, and they did, but even if they didn't it was just one coil and was fairly cheap. So much for progress and state of the art manufacturing

[Dormermike]

Originally Posted by IanS100

There was a time, before manufactures started adding one coil per cylinder, that a coil was expected to last the life of a car, and they did, but even if they didn't it was just one coil and was fairly cheap. So much for progress and state of the art manufacturing

Agree. These engines run very hot though plus all that sound proofing insulation doesn't help.

I think these engines are very intolerant of stuff older engines would be fine with. I notice if mine has done a lot of short trips it will judder occasionally when cruising (stratified running). I think it is a low battery from the short trips.. The coil packs take a wack of poweron their own but the injectors are 250v / 20amp each I believe plus add in the fuel pumps and vacuum pumps and so on and a low battery and the alternator might struggle to keep it all going.

[IanS100]

Originally Posted by Dormermike

.The coil packs take a wack of poweron their own but the injectors are 250v / 20amp each I believe..

I'm not an electrician but surely that can't be right, have you seen the size of cable needed for 240v 13 amps?

[Dormermike]

Originally Posted by IanS100

I'm not an electrician but surely that can't be right, have you seen the size of cable needed for 240v 13 amps?

Yes good point. Perhaps the driver is 20 amp total and the 250v is low current. I know it's variable too, something like 100 to 250v. Tbh I couldn't find much info specific to the n53 injectors but diesel's use piezo injectors too.