Misfire, no compression on cyl 4
 

Folks,

I think my N14 engine on the R56 MINI just bought the farm.
Massive misfire started out of the blue on I-78, car limped home on three remaining cylinders. No forewarning of any kind. Just check engine light on the way home, then loss of power, then intermittent stalling.

Read the codes - there is a TON, but all point to massive misfire all around, and particularly on cylinder 4.
Pulled the plugs - the one in cyl 4 was missing its electrode altogether! Reset all codes.
Put new plugs in, still misfire on cyl 4, car runs on three cylinders. Reset all codes.
Swapped coils around hoping that one is bad - still misfire on cyl 4, car runs on three cylinders.
Ran compression test on cyl 4 - gauge read ZERO compression. I tried on other cylinders to make sure gauge is not broken - sadly, gauge and other cylinders are OK, cyl 4 is not. Could be stuck/bent/etc valve, could be something more dramatic.

Can anyone suggest ANY scenario from the above description that does not end up with me rebuilding the existing or buying a new N14 engine?

TIA,
alex

Seen a couple when visiting the local shop that are similar...
Usually carbon....
Gets so bad...the valve gets stuck....

Guess the damage plug muddies the water....but did it look fresh...like from impact...or possibly from age/defect?

Miss fire
 

Take it to a reputable shop and have them run a leak down test on cyl #4. Because of the damage to the plug I suspect a piece of one of the valves is bouncing around in there. The leak down test will till you if it's intake or exhaust. Also because the miss fire was instant with no warning, I suspect a broken part. At any rate if this is the case a rebuild would be required. :grin:

Next stop, leakdown test.

X2
Do a leakdown test, check to see where its leaking from. Hopefully the valves and not the rings/bottom.

Check for intake valves carbon buildup and clean of needed. If the valves look with no carbon buildup and you still have low compression, the head will probably need to be removed and inspected.

My vote is a blown piston/ring

Plugs were fresh: new set per-emptively installed 6K ago and at 50K.
The electrode is complete missing. The rest of the plug is intact, but fouled-up badly.

May well be the NGK defect. That electrode had to go somewhere ...

a

How would I test whether the root cause is carbon build-up on the valves vs. dropped valve ?

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I'm betting on a cracked exhaust valve. At minimum, you're looking at removing the head and getting a valve job..

That's also my first guess, but really you should get a leakdown test to narrow down the diagnosis.

Could be a broken piston ringland.

http://i156.photobucket.com/albums/t.../piston4ii.jpg

OK, it's definitely an issue with exhaust valves on cyl 4. 100% leak down on cyl 4, all hissing out the exhaust pipe.

What exactly the issue is, I will get to find out myself once I start taking the head off tomorrow. Could be broken valve, could be stuck valve, could be massive amounts of carbon build-up, could be broken spring, could be anything else.

At $135/hr, it would have been cheaper for the dealer to drop in a new engine without looking. I may end up doing the same anyway, but have to take a look first.

After initial shopping around, BMW-rebuilt long blocks with factory 2 year warranty can be had for ~$3,400 + shipping + core deposit. Local NJ-area dealers quote them at between $4,350-4,600 (+ tax + core), so shopping around is mandatory.

Engine valve failure on a non-abused 56K engine is highly disappointing. Dealer not willing to do much to help out (we will charge you only $135 warranty vs $150 regular labor rate) is not surprising, but not much better. Oh, and this is from the best of the 3 dealers around (don't ask me what makes other 2 even worse) !

a

Cracked exhaust valves on these cars is not uncommon, but you should have gotten more the 56k miles. You could still get lucky on this, and only need to replace a couple of valves and some machining. Be sure to post up what you find out and what you plan to do about it. A learning moment for all of us..

I just had a similar failure on my mini... Only both 3rd and 4th cylinder is dead and no compression pressure. The shop that I brought the car to have tested 0 compression pressure on those 2 cylinder and suggested me to bring the car to dealer. The shop said they suspect the rocker arm broke and there was a service bulletin covers it.

The only service bulletin I know of was for the tensioner, am I missing something? My car is at 110k after 6 years, is replacing the engine my only option? Do you guys have any recommendation?

Doesn't mean to hijack the post... But I have been searching online for the last 2 days trying to find similar issues and just ran into this post with a similar problem 😑

I had low compression on two cylinders on my 2006. As a point of reference, I spent $3200 for a valve job at an independent shop (BMW/MINI specialist).

I'm surprised the rate is that low in NYC. Last time I checked about 2 years ago, the labor rate at SF Bay Area dealers was $180/hr.

odobo,
Sorry to hear about your engine letting go. This is clearly a highly disappointing state of N14 reliability.

Given the rocker arm reference, I assume your shop concluded that the issues is also with the valve train. If there is a TSB for N14 valve-train that would apply in my case (suspected exhaust valve issues on cyl 4), my dealer was not aware of it. I doubt they were holding back as it would make the difference between them doing the job and billing MINI USA vs. loosing the revenue.

It would seam a bit to coincidental for two sets of rocker arms to disintegrate at the same time and leave 2 sets of (exhaust?) valves open on 2 separate cylinders. I'm not arguing that that is not the case, but there probably is something else going on.

My dealer claimed to have broached the subject with MINI USA, and got nothing back. I somewhat trust this shop as they were the only one (out of 2 others in the area) to correctly diagnose and execute timing chain job a year ago.
Even with the offer to use discounted warranty labor rate on engine rebuilt (25 hours of labor plus parts = $9.1K) vs. replacement (20hr labor and overall slightly cheaper), it makes little financial and strategic sense not to buy and install a "new" (BMW rebuilt) engine. There are too many issues with N14s, from carbon build-up, to abuse from 15K factory oil changes, to valve-train weakness, and it would suck a lot to rebuilt valves only to see something else give out a few thousand miles later.

If you want to fix-and-dump the car, do what's cheapest.
If you want to keep the car, consider buying and installing a new factory rebuilt engine with 2-year warranty and getting the car a new lease on life.

In my case, I have spare cars and space in the garage, and can afford to tinker with R56 for my own amusement. I am leaning towards pursuing option #2 (will likely cost me ~$4K out of pocket, plus own labor). Time is a luxury I can ill afford to dedicate to this experiment vs. work and family, but even if it takes me a month or two to get through it, it has a certain educational value for the kids. We just finished building a mechanized Lego-Technic F1 car with them, so now it's time to go to play with full scale model ;-)

a

Last year, our '08 Clubman S bent the intake valves on #2 due to chunks of carbon being ingested. symptoms: destroyed #2 sparkplug and zero compression on #2 ($4200 @dealer to fix) No warranty @111,000 mi.
This year, a cracked crankcase vent hose caused a lean condition which sent the engine into a tizzy(technical term for erratic running and CEL). $839 later, a new hose and a new thermostat housing(and a multi-point inspection). It ran fine on all four until (on my way home from the dealer) I accelerated on an on-ramp in 4th gear and a major tizzy reoccurred. Made it home on three and had AAA take it back to dealer. Dealer now says burnt valve on #3 due to lean running condition. I'm expected to pay them another $4200 since it is "not related" to previous experience. I'll be damned...

Hi Afadeev,thanks for the advice. I figure that after 110k miles the dealer probably won't help much except trying to charge me a arm or a leg. I do like the car and intend to keep it... I just cant find a replacement that can give me the gas mileage as well as the fun to drive in the market. Can you share me some info on where can I look/buy the BMW rebuid engine you were talking about? I tried looking online but only saw 1 place that sell a mini rebuild engine... Otherwise I can only find them on eBay which I don't know if I can trust them.

O

OK, the 56K mile old engine had been removed, and is now sitting on a dolly. The new one is bolted to the tranny, and is now sitting inside the engine bay, getting all wired up. I wont be 100% certain about what went wrong until I take the head off, but something unnatural happened in cyl 4, most likely resulting in terminal damage to the exhaust valves, piston rings, or both.

Once I took out the intake manifold, all intake valves were gummed up beyond belief. I'm surprised they were sealing and passed leak-down test. Except for cyl 4, where intake valves were shining clean. I tried taking a few pics, but it's surprisingly hard to focus the camera and get correct exposure through the intake ports in the head. I will post more pics once the head comes off (I'm more interested in getting the new engine to fire up right now).

On the exhaust side, the valves looked OK all around. The only thing that gave away trouble in #4 was excessive amount of oil all over it. I am enclosing a few pics of the exhaust ports and valves to give an idea.

Oil was present in the intake manifold and throughout the intake piping. It took me a while to take everything apart an clean it all, but I believe I got 95% out. The rest will get trapped by the oil catch can that will be joining the engine bay.

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What happens when the valves have carbon deposits on the head of the valves (in combustion chamber) the carbon starts to glow and absorb heat eventually weakening the valve to the point that part of the valve breaks off (link). If one can maintain the carbon buildup by having valves blasted every 30k-40k miles and use BG 44K to keep carbon at bay all of these problems go away, I run a can every other month. Nothing can match BG's 44K clean up of carbon in combustion chambers, it's pricey though, but then again so is the cost of a new engine!

The only carbon buildup I've seen is on the intakes, and not in the combustion chamber but on the intake side of the valve itself. It's conceivable that a chunk could get loose and block open an exhaust valve causing it to burn. The remedy there would be to do a valve job - I can't image a valve job costing $4K.....anywhere!


OP, did you ever have the walnut shell blast done on the intake valves? I did it on my 56K mile car recently and mine weren't too bad, I did it as a maintenance/preventative measure.


I would have pulled the head before agreeing to a new engine, just to see what was up.


I would definitely contact MINI USA yourself to ask for goodwill or help on this repair, since you're so few miles out of warranty. However if you decide to do this you need rec'ts showing you changed the oil regularly and used the correct oil and filter for your car, otherwise they won't be inclined to help.

Well, it's sorta nice to see I have company. My '07 MCS N-14 engine with 79,000 miles just failed (out in the middle of nowhere). Drove 450 miles on 3 cylinders to the SLC dealership. Bore-scope shows broken #2 exhaust valve, damage to piston top and cylinder walls. Elected to go with a new engine, new clutch package, trans seals, coolant hoses to create a zero-mileage 8-year old car, since I plan on keeping it long term anyway. A new engine was about $2K more expensive than repairing the original motor.


This car is an early '07 model when we had to wait in line to order one. The engine was clearly not ready for prime time - 4 timing chain/tensioner replacements, HP fuel pump, both water pumps. I had the walnut-clean treatment done to the cylinder head at 60K - which really improved the engine performance. Pre-clean photos were truly ugly to see! Aside from engine issues, the rest of the car has been flawless since new. Truth be told, I'm happy to get rid of the old engine - it's been a pain.


The service rep sez this crate N-14 engine was assembled last year, so hopefully has all the latest N-14 mods and improvements. Includes all accessories and new turbo. Also 2-year warranty. Wife is OK with the expense since I had planned to keep the car forever, but sez if it breaks one more time, I'm trading it in for a Miata ...

You'd have to like the car a lot to put that kind of $$$ into an 8 year old unit. Unfortunately, its still an N14 with all its inherent problems. Trying not to be a downer, just doesn't make sense to me...

Good Luck

Run the #s, it may start making sense.
Brand new (and/or factory rebuild) N14 can be had for ~$3.5K from select MINI dealerships. If you can DIY, with a few extra tools you will have a brand new engine for under $4K. And that buys you a new water pump, oil pump, thermostat, spark plugs, removal of all oil leaks from your current engine, and removal of any and all carbon deposit on the intake valves. Basically, around ~$1.5K worth of goodies that your current N14 already needs, or will need real soon now.

The alternative is to ditch the R56 for scrap metal, to part it out, or sell it to someone else who is willing to repair it. Figure $500-$3K at most.

As long as you R56 is worth more than $4.5-$7K, you are way better off fixing the car and enjoying the brand new engine for at least another 60K miles.

Even bare bones clean first-year '07 MCS still go for around $10K these days.

Add a bit of curiosity, and a tinkering bug, and a dropping in a new engine becomes an obvious course of action for any DIY guy.

If you can't DIY, or are sick of your car, than the decision tree branches differently.

a

Thanks for the comments. Since I elected to go for the new engine, I also replaced all belts and rubber hoses, "renewed" the transmission (clutch, seals, etc) since it was already in parts on the shop floor. I have nothing but applause for MINI of Murray (Salt Lake City) for working with me. Just turned over the 1,500 mile break-in point and the car seems to have seriously more zip than the old motor had - or maybe it's just all that money talking ...:wink:


I sent off a nasty-gram to BMW-USA, mentioning that today's auto consumers expect modern engines to last more than 80,000 miles - even if it is a British motor. I requested they "participate" in the engine repair as a matter of loyal customer good-will (I've owned 2 MINIs) even though the car is way out of warranty. They sent back a check to cover 25% of the cost!:thumbsup:

Wow I wouldn't have thought they had it in them. :eek:

I had the same problem. I changed the number 4 and number one ignition module. This solved the problem. The connection was a bit corroded. Just swapping probably scrapped some of the stuff off. Then I cleaned it and it ran about the same. Pretty darn good. For the brave of heart. Take out the number four plug before the next oil change. Use one of those long skinny auto transmission funnels and pour a whole can of seafoan down into the the piston and let it sit overnight. Replace the spark plug and crank it up the next day. It seemed to get rid of most of the carbon though it did smoke like hell for a few minutes. Before the next oil change do the number one piston the same way and be sure to change the oil afterwards. Continue to go through all cylinders until you've done them all. Make take a year of so. Or you can take it and have the walnuts shot into the manifold and pay a few hundred. Can only say it worked for me. 141,00 and still going strong.

ThumperMCS wins the brownie points on this one.

I finally had time (a year later!) to pull the head on the old engine, and to my surprise, all valves on cylinder 4 looked just fine (pic #1 below). However, pistons didn't look as pristine (pic #2), and piston #4 in particular seams to have a piece missing (pic #3) with some cylinder wall scarring to go with it.

I still do not understand what happened in cylinder #4, but the residual damage is that the spark has lost its electrode, and a piece of cylinder #4 has gone missing without a trace, and scarred the cylinder head.

Weird.
Any ideas on what could have transpired?
Any thoughts on whether the block can/should be salvaged?

TIA,
a

Interesting I wonder which happened first, the electrode falling into the cylinder or the piston failure. Depending on how big the broken piece of piston is it's possible it made it into the exhaust manifold, hope it didn't come into contact with the turbo compressor. I think your alright cylinder wise if you machine the cylinders, you might as well replace all the valves and pistons and rebuild your engine. I'm assuming you'll do most of the labor, now is your chance build it with stronger pistons and rods.

This entire causation sequence remains a mystery to me.

The fact that the piston would loose a chunk, even if there was excessive detonation, is extraordinary. I have to assume it went first, as I can't imagine a scenario where a broken electrode would take out a piston. I could see it bouncing around and damaging one of the exhaust valves on the way out (not present!), but taking out a piston - that would be remarkable.
My present working assumption is that excessive denotation, causes unknown, was not properly mitigated by the knock sensor + DME, and that produced enough of an explosion to both take out the spark plug and the chunk of a piston.

The one remaining mystery is where the chunk of that piston went. It is too big to have exited out the exhaust valve hole without causing some damage to the valve (again, exhaust valves are not damaged!!), the only other place to go would be down past the crankshaft to the oil pan, but that path is not viable as only the top portion of the piston is damaged (there is no through hole).

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same thing happened on my car around 75k. #3 died. unfortunately, they didn't let me keep the old engine, so i couldn't tear it down to see if the valve or the piston died (couldn't see a hole in the piston with the boroscope i had before i took it in).

I asked the tech the same thing when he was replacing my engine "well, if something broke off and shot out...it had to go somewhere right??" he actually let me inspect the turbo once he got it out and it looked fine. from reading many of the failure analysis threads on here, seems like 50/50 chance either a valve broke, ring broke, or piston melted (although, my engine finally failed under a steady cruise while still getting up to full temp, so i doubt that).

Forgot to comment on this bit - when I replaced the engine last year, I did inspect the turbo and there wrtr zero signs of wear on the blades. It is working just fine with the new engine.

It is hypothetically possible that the piston chunk did not break off in one piece, but in multiple shards, that made it past the exhaust valves and were routed straight into the cat (if the waste-gate was closed).

I would be doing most of the labor, but if I proceed with the rebuild of this engine, it would be a spare / fun project. The rebuild engine would go into one of the N14 donor cars that are popping up with blown engines with a disturbingly increasing frequency. :eek:

Does anyone have a lead at a shop in NE that could machine the block?
Some experience with MINI's would be plus.

TIA,
a