SES + Rough Idle = Cracked Plugs

[TUDM]

The 3 has been sitting in the garage all week. Hopped in it this morning, fired it up and UH-OH ... could tell right away that it was misfiring on at least 1 cylinder. Let it idle for 30 seconds and up pops the SES light. Turned it off. Started it again and the exact same symptons ... noticeable misfire and SES light.

Climb in the Xterra and go to work. Think about all the ignition coil problems I've read about. So I call the dealer, explain the problem and schedule an appointment.

Go back to the house at lunch to pick up the 3 and "limp" it to the dealer. I'm expecting the worse ... a coughing, stuttering, "I can barely make it" trip. To my surprise, the 3 fires up and idles smooth as silk! The SES light is on; but otherwise runs just fine.

So I drop it at the dealer and here's what they tell me: Faults 242 and 238 ... cylinder 1 and 5 ... check all coils passed ... remove plugs 1 and 5 cracked. WTF! In 20 years of driving and motorcycling (also doing a lot of the maintenance on bikes and autos) I've never encountered a cracked plug! I asked the service manager about this and he said it wasn't common, but he had seen it before ... mainly with the older 30000 mile plugs.

Live and learn. Oh well ... at least I got to take a few hours off of work for my favorite activity ... driving the 3 !

 

[Akakubi]

That is indeed wierd. I've never heard of cracked plugs on an E46.....[???1]

But them saying "older" plugs at 30K miles is funny. BMW claims that they should easily last 100K miles before requiring replacement. [fake] So much for their own claims.

I just swapped my plugs yesterday at 28K miles. The OEM NGK's were looking fairly worn. I had a slightly unstable RPMs at parking speeds and hesitation between 1500-2000 RPM when the car was cold. The dealer had no fault codes showing....

So I swapped the plugs for the Denso Iridium. And wow, it's like having a chip installed. Throttle response is much faster and no more hesitation. The car feels like never before.

 

[TUDM]

I didn't mean to imply that my plugs were "old" ... the context of the conversation was (my thoughts in italics):

Me: I've never seen a cracked plug?

Service Advisor: It's not common, but I've seen it before. Not in the newer 100,000 mile plugs (he was referring to the 100,000 mile interval on spark plug replacement for E46s) , but in the older 30,000 mile plugs (whatever they used before the 100,000 mile plugs).

I'm not sure why the plugs cracked ... some of my random thoughts:

• technician accidentally cracked the plugs when he removed them
• faulty ignition coil zapped the plug with way too much energy

I'm pretty sure faulty coils caused the plugs to fail. But I've got no way to prove it. No big deal, just glad to have the 3 back on the road.

 

[Akakubi]

I didn't mean to imply that my plugs were "old" ... the context of the conversation was (my thoughts in italics):

Me: I've never seen a cracked plug?

Service Advisor: It's not common, but I've seen it before. Not in the newer 100,000 mile plugs (he was referring to the 100,000 mile interval on spark plug replacement for E46s) , but in the older 30,000 mile plugs (whatever they used before the 100,000 mile plugs).

I'm not sure why the plugs cracked ... some of my random thoughts:

• technician accidentally cracked the plugs when he removed them
• faulty ignition coil zapped the plug with way too much energy

I'm pretty sure faulty coils caused the plugs to fail. But I've got no way to prove it. No big deal, just glad to have the 3 back on the road.

Oops, my bad. Misread your post.

Coils may be the culprit. Hearing about several guys complaining about them, that could be very much the reason.

Glad they fixed it under warranty.

 

[bmwrocks]

That is indeed wierd. I've never heard of cracked plugs on an E46.....[???1]

But them saying "older" plugs at 30K miles is funny. BMW claims that they should easily last 100K miles before requiring replacement. [fake] So much for their own claims.

I just swapped my plugs yesterday at 28K miles. The OEM NGK's were looking fairly worn. I had a slightly unstable RPMs at parking speeds and hesitation between 1500-2000 RPM when the car was cold. The dealer had no fault codes showing....

So I swapped the plugs for the Denso Iridium. And wow, it's like having a chip installed. Throttle response is much faster and no more hesitation. The car feels like never before.

Naturally cracked plugs, yeah right. Never seen or heard of it. I think they cracked em geting em out, or else they are just flat lying which is more likely.

There is no such thing as a 100K mile plug contrary to anyones claim.

Good move Akakubi, I say get em out of there at 30K, reinstall better ones using plenty of anti-seize, so you won't have to break them off later.

I have never heard of Denso Iridium, I am guessing they are high quality?

 

[Akakubi]

Yeah, Iridium is the new "thing". There are two companies that manufacture them: NGK and Denso. I was reading up on both and decided to get the most extreme (though priciest too). There are minor differences between the two brands with more performance going to Denso and a bit more longevity to NGK.

Here's one write-up I found interesting comparing the two:

http://www.spark-plugs.co.uk/pages/technical/iridium_spark_plugs.htm

 

[jonnyz16]

Thanks for the link man . The strength and temp thresholds are amazing..I'm coming up on 30k myself.maybe I should change the plugs already ..

 

[Akakubi]

Thanks for the link man . The strength and temp thresholds are amazing..I'm coming up on 30k myself.maybe I should change the plugs already ..

Yeah, at 30K I bet it's a good call to swap them.

The two most inner plugs are a bit PITA to extract. The wrench will not clear, so I used a magnet to "fish" them out.

You'll need a 10mm socket for the coils and plastic engine cover and a Plug wrench.