Hey guys, I can really use your help! To provide some background, this is regarding my wife's 2010 MINI Cooper base, ~91K miles. The car has been throwing a P0420 code on and off for over a year, but it has always run fine. A couple of months ago, she took it to the dealer for an oil change, who sent her home with a laundry list of work to be done, including a new valve cover, though the reason for this was not specified.

I took a look at the VC and it looked fine, although I did notice some slight oil leakage at the gasket. I figured it just needs a new gasket, and the dealer (who has proven to be criminally dishonest in the past) was just trying to rip her off. Before I got around to changing the VCG, the car started running a little rough, hesitating slightly during acceleration. There were no misfire codes but it felt like that might be the problem. When I went to try swapping out the coils, I noticed that there was some oil in two of the four spark plug wells. Clearly, the VCG needed to be changed without further delay!

Yesterday I changed it. Process went smoothly and I was super-careful to ensure that the VC was properly seated during the reinstall. Now, the car runs substantially worse. It idles roughly, with RPMs swinging between 600 and 1900. When driving, it often stalls when the car stops, and then doesn't always go when I give it gas. I tried swapping out all the coils and all the spark plugs--makes no difference.

Two thoughts come to mind. First, is it possible that despite how careful I was during reassembly, the gasket is not properly seated at some point? Anything's possible, but I inspected the perimeter with a mirror during and after the process, everything looked and felt fine, and the VC was properly torqued in the correct sequence. Still possible of course, but I'd be surprised.

The other thought--and I don't honesty know if this makes any sense at all--but perhaps there was a ventilation (PCV?) issue that was made worse with the new VCG, now that there's an airtight seal between the VC and cylinder head. If it helps at all, I'm now getting--in addition to P0420--P0303, C342D, P0055, and P115G.

I have some temptation to replace the VC like the dealer advised, but I hate to throw nearly $400 at a problem with no strong reason to believe that it will solve it...

Thank you, and I'd be grateful for any advice you can provide!

 

So, in my humble opinion, you have a vacuum leak, either from the cover not being sealed correctly (did you put sealant on the rear right corner angles?) or you have a damaged PCV hose, the one which goes from the cover down under the intake (the one that is a b***rd to get to and check). Your O2 sensors are being upset by high emissions going by the codes.
On another tack, 91K miles is way beyond where I would be comfortable without a timing chain being replaced as when they elongate it puts the timing into retarded and can cause rather nasty guide rail breakages and pretty much eats your valve stems. Running a while with a retarded engine will damage the O2 sensors and cat - but that is not a sudden thing, and your symptoms appear sudden... Look for a damaged hose but since it is sheathed it is hard to tell without taking it out (and that is a b*tch)

 

I think Scudder44 is correct. The breather hose is made of thin plastic that is very easy to break when moved. It is difficult to tell if is damaged due to its location and any small cracks will throw off the engine managment calculations as unmonitored air is venting through the cracks. I would double check your chain tensioner bolt too. If it was somehow loosened during the VC replacement, it too could cause some issues. Replace it to the upgraded part if you have not already to limit potential timing chain issues. If you have not replaced the breather hose yet, it is time to do it anyway.

I am beginning to realize that after about 10 years, these are all basically maintenance items: valve cover gasket, breather hose, chain tensioner... and I would add to that the crank case oil seal / maybe pulley. Good luck and let me know if you need help. I just replaced mine a few months ago.

Make sure you connected the mass airflow sensor and intake correctly too.

 

One more thought: There is a “flapper” in the valve cover gasket. It is basically a red/orange rubber disk. I have not replaced this yet. Mini-is-for-me recently replaced hers. Take a look at those posts. This may be a component to your issue as well.

 

Thank you all for the responses! I'll definitely take a closer look at all these things, especially the breather hose--I've had this break on another car while doing a VCG change...

Do you have any strong reason to believe that the VCG (or PCV system) has failed? Would a better VCG seal exacerbate a PCV problem, making the symptoms drastically worse?

Thx again!

 

It sounds like you know what you are doing, so I would not assume a a VCG seal issue. Usually you would see a significant leak were it not sealed correctly. You inspected for one and did not find any. I would remove the small cover and inspect that “flapper” as something may have happened to it during the VCG work.

I do not know the correlation between VCG seal (if indeed now better) and PCV function.

 

OK, thanks again!

 

Ive been searching for information on my wife's 2013 Mini Cooper S that is exhibiting the same problems - rough idle, stalling, big check engine light (don't know the codes yet). The PCV hoses on the car have oil residue on them. Sounds like I might be dealing with the same problems. This Mini only has 60k miles. Going to trade it in once it's fixed before th $%#@! thing bankrupts me.

 

Hey guys, I took another look--hoping to find a damaged breather hose--and here's where I'm at:

-- No visible damage to breather hose. While I only inspected the top part of the hose that's accessible, it seems solid, there was no give or sound if I (carefully) squeeze it, it can move around a bit, but seems to be attached at the other side,and when I move it around with engine running, the movement doesn't seem to correlate with the roughness of the idle. Can't rule it out, but no conspicuous evidence of failure.

-- I inspected the perimeter of the valve cover. Everything's clean and dry; the VC gasket and seal seem to be intact.

-- About checking the flapper, I saw the thread about removing the cover for an N18, but the N12 is a bit different... Any advice on how to remove this? Also, is it risky to remove this and risk breaking it without a replacement on-hand? One other question about this: If this were a PCV issue, would there be a strong vacuum when trying to remove the gas cap with the engine running? If there is NOT a strong vacuum, would that suggest no PCV issue?

Thanks for your advice; I'm seriously not sure what to do next...

 

Almost impossible to remove the diaphragm cover without breaking at least one tab as you can only get to one tab and they are very fragile. Unless you are sure there is a leak leave it alone. Time to move onto some other cause. Choice is yours but I would now be looking at the timing chain. If you can get your hands on the timing chain/cam tools there is a dummy tensioner in the box which you can use to measure the chain stretch and see if you are out of tolerance. More than 68mm and time to replace. I am presuming the chain is original.

 

Thanks again, Scudder... I'm definitely not sure (and not even that confident) that there's a diaphragm leak...) I'll look into timing chain tools--you're right that the chain is original!--though it seems unlikely that this would cause my sudden, severe symptoms. Let me ask: If I wanted to more-fully inspect the breather hose and possibly replace it, do I need to remove the intake manifold? (This is on an N12.) If so, are you aware of any good DIYs? (I looked but couldn't find any.) Thx!

 

If you have an issue with the PVC diaphragm, it’s the oil cap that will be difficult to remove while running, not the gas cap. From what I’ve seen the N12 diaphragm isn’t very much different. It can totally be done without breaking the tabs if you are careful and take your time. Check the oil cap to see if it’s under vacuum.

 

My bad--I meant to say oil cap! There's a light vacuum but not strong at all, which is why I'm skeptical of there being a diaphragm issue... Thanks!

 

I had a feeling, but I’m a smart aleck and couldn’t resist pointing it out..... if it’s not difficult to remove the oil cap while running, and when it is, if the idle doesn’t really change, then it’s probably not the issue, unfortunately.
Good luck!

 

Arb63: Yes you do need to remove the manifold, but it is not too bad. To the best of my recollection, there are 6 nuts holding the intake to the head, then there is the intake filter assembly and a few wires to remove from the top. From the bottom, there are i think 3 bolts and one or two electrical connections. All are pretty visible. One was a PIA with my fat hands. It took me about an hour to get off and maybe 20 minutes to put back on. Finding the right breather hose was difficult for my year. But I think you will be fine.

 

OK, great, thank you!!

 

Yeah, the manifold is pretty simple. A few nuts up top, and remove the charge pipe from the throttle body, then there is one 10mm (irrc) bolt down below the throttle body. I have to find it by feel every time. Remove those and the purge valve and pressure converter will slide right off of their mounts. And that’s about it.
good luck
Pelican parts has a few really decent diy guides too

 

Thanks!

 

Here's an interesting new development... I took (yet another) look around the perimeter of the valve cover looking for any evidence of a leak, and noticed today that there was some oil pooled in that little U-shaped dip on the left side (passenger side), near the front! Obviously I will need to remove the valve cover and try to address this, but could that small leak be the cause of these significant symptoms??

Interestingly, it was this same location where the previous gasket was leaking the most... Makes me wonder if the valve cover is slightly defective or became warped in this area? Still doesn't explain, though, why the symptoms weren't there with the old leaky gasket...

I'm thinking that I'll place a healthy dollop of RTV sealant at that location, when I reassemble.

Two other questions: (1) Do you see any issue using the same gasket that's just a week old? (2) While driving the car in its current state, my wife believes that there's more white smoke in the exhaust than usual (though she's not certain.) Does this indicate anything?

Thanks!!

 

I would get a new one just incase it moved or reformed due to heat. Makes sure everything is sealed up. Once the valve cover area gets a pressure drop the engines start to stumble, like when you remove the oil engine cap which its running on the Gen 2 MINI.

That might just be the colder temps outside.

 

Thanks, and yes, a new VC might be the solution... Just hoping to avoid the expense if possible, or at least have a high degree of confidence that that will fix the problem!

 

...Scudder44 for his diagnosis of "vacuum leak"! (Plus honorable mention to Lancaster, who quickly agreed, and followed up with some great addition info!)

Here's the situation, in case this is helpful to others... I mentioned a few days ago that I noticed some oil collecting on the wrong side of the gasket, in that little U-shaped dip on the left side. My plan was to remove the cover again and apply some RTV on that spot. Yesterday, when I removed the valve cover, I noticed something else that was interesting... While I was loosening the bolt in the front left corner, it didn't unscrew easily... Rather than using a tool to loosen it and then using my fingers to unscrew it the rest of the way (as I did with the others), I needed to use a tool to remove almost the entire thing. Clearly, the threads weren't clean. Which made me wonder if that could have been the problem. While the install looked fine visibly, perhaps some debris on the threads prevented the bolt from completely fastening the cover to the cylinder head, even thought it was properly torqued. As this is very close to where the oil was collecting, this seems like another plausible explanation.

Anyway, when reinstalling the valve cover, I did two things: (1) I thoroughly cleaned all the bolts, making sure they were free of all debris and dried Loc-Tite, and that the threads were undamaged. I also blew out the "receiving threads" and made sure they were free of debris, and finally, I did a "dry-run", screwing a bolt into each hole making sure they all screwed-in smoothly and easily. (2) I also applied some RTV to the "dip".

The result? Problem completely solved. Runs smoothly, accelerates smoothly, no stalling or stumbling. I may never know which tactic (thread cleaning or ATV) actually solved the problem, but I can live with that.

The only possible issue I now have is that I noticed a very small amount of oil at the gasket, along the front. (It's only visible when shining a bright light on it.) Perhaps the gasket didn't like being uninstalled and reinstalled, and I need to get a fresh one. I'll monitor it closely over the next few days...

Thanks again to everyone for their help!

 

Glad you got it figured out and it was an easy fix.

 

+1 glad its figured out. Happy motoring now.