We are the original owners of this justa Cooper 6 speed with 95K miles. At 80K+ it developed an occasional misfire, at low (maybe 1800) RPMs under moderate acceleration, and when I inspected the spark plugs they were seriously worn and replaced with OEM which solved the problem.
Fast forward to more recently, and the occasional misfire has returned. I found oil in the number 1 and number 2 spark plug wells and replaced the valve cover gasket for the first time. I also replaced the thermostat / housing at the same time because I detected a slight coolant leak on that side and that, too, was original. Although I fixed the oil and coolant leaks, I am experiencing worse misfire. Instead of a single "bump" I am now getting more than one sometimes. It only occurs around 1600-1900 RPM and never about 2K. The engine otherwise runs great and continues to get excellent fuel economy on the order of 40mpg. I only use premium 93 octane fuel, and it seems independent of fuel vendor.
My guess is this is an ignition problem, and wondering whether the ignition coils could be weak.
There are no check engine lights or other idiot lights showing when this happens.
I'm open to suggestions.
BTW, I'm not into "lugging" the engine, but there are times when one uses the engine below 2K for a slight to moderate acceleration, which is how we've driven this for the last 95K miles, so it isn't an issue of not driving properly, this is something wrong with the engine running.

Jim

 

Make sure you are not low on oil, it will misfire like that sometimes when down more than a quart. No CEL codes yet? Could be dirty air filter or what ever part is a mass air flow sensor. And lastly, spark wires or coil - what do the plugs look like now?

 

Have the timing chain tension checked. They appear to go bad in mid-life, and can cause many other troubles.

 

I have read a couple of threads here where a coil went bad on an N14. For those examples, the misfire was bad enough that an error code was present (misfire Cylinder 2, for example). Using a scanner, it was found that the misfire followed the coil (if the coil from cylinder 2 was put into cylinder 1, the misfire would switch to cylinder 1). A fresh coil (or set of coils, depending on your budget) fixed the problem.

I don't know for sure if the coils are the same from N14 to N12, but I would see if there is a code or two in your car's memory.

Mike

 

Here is an easy thing to do. Buy 1 coil. Then swap it from cylinder to cylinder until the misfire is cured. Of course if the misfire occurs at every step, the problem is not secondary ignition unless you have a bad spark plug.

 

On my 08 Clubbie when it had this issue, they did plugs, then coils, and in the end new cables put an end to it. She was still under warranty at about 40k when it started.

 

Update on misfire problem:

I ordered 4 new coils from an online vendor. Was only around $110 total, shipped, for 4 Bosch coils. Previously, I had no CEL triggered, but after the installation I immediately had a code for misfire cylinder 2.
Turns out, I did not have the connector plugged in quite far enough. Even though these appear exactly the same, they are much more still plugging them into the spark plug holes in the wells, and more stiff when plugging in the harnesses to the metal locking devices. Once I discovered I had not made an adequate connection, and i cleared the code, everything seems great and the car no longer had misfires or hesitation.

So, in reading the Bentley manual, it suggests the coils are very sensitive to damage from oil or gas, and since I had the leaking valve cover gasket with oil in the spark plug wells, I felt that might have been my issue. Apparently it was. And seeing how relatively inexpensive the new ones were, I went ahead and bought 4 new coils. Problem solved.

Jim

 

Quick update for the record: Swapping out the ignition coils solved my intermittant hesistation / misfire at around 1800 rpm, and the car runs fantastically well and smooth now.
I dare say you'd be hard pressed to know whether this car had 10,000 miles on it or the actual 96,000 miles. It runs that well, handles that well, and if I detailed it thoroughly, would look that good, too.

 

Hey Jim.

So did you do your valve gasket cover yourself? how much was it? where did you get the part from?

 

Yes, I did the valve cover gasket myself. I can't recall the price but maybe $50 or so. I remember being shocked at the price but I bought it directly from the dealer and I suggest requesting a NAM car club discount, because I found out later when I bought the thermostat housing that my dealer does offer a significant discount and it helps!
Anyway, I took tons of pictures along the way with my cell phone and never referred to them. I did the gasket at the same time as the thermostat, so the disassembly for each job overlaps somewhat. I can't tell you how challenging it would be to just do the gasket but I would say not very much.
Ignoring the oil leak into the spark plug wells caused failure of the coils, which cost me another $100 + for replacement of all 4. Car runs great again, and no leaks. And at 97K miles, that isn't a horrible cost or maintenance experience overall. The coolant was due to be changed anyway.
Jim

 

Any tips on how to replace the VC gasket? My friend has a 2009 Justa Clubman and I was hoping to replace it for her.

 

Take a bunch of cell phone pictures in case you want to refer to them for reassembly, and refer to a good manual. I own the Bentley manual.

 

I don't have the Bentley yet, but I do have a Haynes manual which is considerably less detailed. Is it a straightforward job or will I need to familiarize myself with any parts that are tricky to remove/reinstall?

 

Honestly, I don't recall that it was a difficult job, but it has been a year. I've been a "backyard" mechanic for about 48 years, and I have a good collection of tools and a nice shop in which to work.
Just proceed logically and carefully. Keep everything clean and organized, and don't drop anything inside the engine or cylinders. Pretend it's surgery, clean and careful!
If you get stuck, post back here and somebody will try to help. If you have specific questions you could PM me.
Jim

 

...

 

Thanks Jim! Will do!

I've replaced many a VC gasket on my VW Rabbits, Cabriolets and Foxes. I've also replaced the plugs in my former ride, a 2001 GTi 1.8t.
I would expect it's not much more complicated than removing various covers and disconnecting any hoses or wires that get in the way.

 

its pretty easy, just remove all the coils and connectors attached to valve cover, pull all the 10mm bolts and the one 8mm nut that secures the ground and remove the valve cover. clean with some brake clean and a rag where the valve cover meets the head and thats it. don't forget to tighten the 8mm nut for the ground

 

That sounds easy enough! My friend was quoted $650 by her local dealer to replace the VC gasket. I was beyond shocked.

 

they over quoted her, i believe the labor time is 1 hour and the gasket isn't too much. id assume the price from a honest dealer should be around 200

 

Should I tell her to buy a gasket from the dealer or is there an OEM aftermarket brand that works just as well?

 

im not too sure, if it was me i would just use an oem gasket, but thats just me

 

2Fast2, I'm in the same situation as you were. I have 2010 N12 hardtop and experienced misfires around 75k and took it to a local shop. They found the bad coil #2 and replaced it as well as all the spark plugs. Now at 97k I'm experiencing the same misfires around 1800 rpm and got a new Bosch coil and planning to replace it on 1 thru 4 to see if one of them would cause the misfires.

Thanks for the updates and glad you resolved the issue.

jh

 

Just make sure you don't have an oil leak causing the coil to fail.
I do believe, at that mileage, if you have to replace one coil you might as well replace all 4, with 4 new plugs. But if any of the plugs come out with oil on the porcelin, then you've got a valve cover seal leak and you need to fix that or you'll risk ruining the new coils as well.
Good luck.

 

ahh… It seems I have what I was afraid of. I pulled out the coils and the #1 coil had some oil residue. I looked inside and oils all over inside. It seems there is an oil leak, possibly from the cylinder cover seal. I'm not too comfortable to open up the cover (not much experience and I don't think I have a right tool either), so I think I need to drop by to the local shop. Can someone give me good suggestions how to clean up the oils already inside without taking the valve cover out?

Thanks.

jh

 

take a paper towel and wick up around the spark plug.

The problem is oil leaking from the valve cover seals that go around the spark plug wells. If you have a misfire, I think you've damaged that coil. You need to replace the valve cover gasket and that corresponding coil, at a minimum.

This is a known problem and the dealership parts guys were very impressed that mine lasted 80+thousand miles. Same with the electronic thermostat. They said many have already gone through more than one replacement in that many miles.