Hello all, I will try to keep this short but also want to give as much info as possible in order to solve this problem. I have a 2007 Cooper S automatic with 84000 miles. I bought the car used almost three years ago and about 6 months after that I noticed that when i drove the car in stop and go traffic it would Idle really bad. When i came to a stop the engine would rev from about 7000 up to 9000 a few times then quiet down till i came to the next stop. It stills does it till this day and its driving me crazy. One very important note is that i have never gotten a CEL the whole time ive had the car. Ive tried a few things that have been suggested by two different well reviewed Mini mechanics. First shop suggested a carbon cleaning with just a chemical solution and told me to add Chevron with Techron every 3000 miles. This did quiet the problem for about 6 months till it came back. Next shop suggested a possible fuel pump problem but said i would have gotten a CEL by now. They kept it over night and ran some test but only ended up catching a slight misfire in cylinder 3. They replaced the coil and said hopefully it fixes the problem. It didn't .
So ive done some searching and have found people with the same problem but the threads are never resolved. I bought a OBDII and Torque app and have been logging some drives. I did notice under The vehicle test results that i had a red/not OK O2 Bank 1 Sensor 1. Is it possible i have a bad O2 senor? Also this problem only happens when the car is warmed up and driven kinda hard. Thanks for any help and sorry this post was so long.
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The chemical carbon cleanings don't really work. You need to media blast with walnut shells. Independent shops should do this for under $400.00. If you have never done a real carbon cleaning then you are way overdue. It's worth taking a look at the valves.

Have you pulled your O2 sensor and looked at it? I'm not an advocate of just replacing parts but the O2 sensor is not really that expensive. If you think it is your HPFP, I believe that some apps can log fuel rail pressures. MINI did increase the warranty on them for some model years.

Also have you looked at your spark plugs?

 

Both shops have told me they don't want to do a walnut blasting till a CEL comes on. I actually insisted on the chemical cleaning back then for peace of mind and when i picked the car up the shop told me there wasn't that much build up. I don't know if i have a rare r56 s but mine doesn't go through any oil. I went 8000 miles in between my last oil change and never had to top off the oil. I was even so paranoid that i was checking it wrong that i dropped $80 bucks on the Craven aftermarket dipstick.

I'm not mechanically inclined to pull the sensor unless i was shown exactly where to find it and then how to see if its bad. Is it easy?

The last shop said they didn't think it was the fuel pump either because it didn't show any symptoms when it was cold.

 

Removing the O2 sensor is simple. It's the thing that it protruding out of the heat shield. It would be nice to look at the condition, same with the spark plugs.

It does require a special $10 tool available at any auto parts store. If you're not comfortable doing this then don't do it. Murphy's law will kick it and you break something and it will cost you a small fortune.

 

Do you have a mini dealer close by? The mini lots a lot of computer codes that not all shops are equipped to read. Have you had the timing chain recall done? That could be a good reason to go to the dealer and have them work on the car and have them look at the idle issue while they're at it. They have diagnostic tools for seeing if the HPFP is failing (it's a common failure).

Unfortunately it doesn't seem like you have a bad enough issue that we can really track down the root cause. Certainly not over the internet based on some descriptions and a few phone screenshots. It could be any number of things so it's hard to do anything but suggest replacing parts until we happen to stumble upon the solution.

 

In the past when my last BMW told me I had a bad O2 sensor (twice), I replaced it and all was good. Not sure why the hesitation in replacing that part? Go with OEM part.

 

To echo what was said above. A chemical cleaning doesn't work, you have to media blast it. You won't necessarily get a check engine light when you are in need of valve cleaning. Also, if you HPFP is going, you most likely will get a check engine light, typically for random misfire codes.

Lastly, unless it's physically damaged (as in broken wires going into it), you're not going to be able determine that your O2 sensor is bad by looking at it.

 

+ carbon build up.Often does not cause the CEL and common cause-and-effect is defective O2 sensor because fuel/air mix. goes bad.Just clean the valves and replace a new o2 sensor.

 

O2 sensor is as good a place to start as any. But get the oem one not the aftermarket.

Maybe your car is a unicorn, but there are a lot of problems with that N14 engine and oil changes are the cheapest thing you can do to keep that car running.

 

I have always leaned towards the carbon blasting given it being a common problem and the cars milage. Does anyone know how much it cost to physically take the head off and verify if I have dirty valves? I Dont have the car fax anymore but I'm 90% sure that the fuel pump was already replaced under warranty by the previous owner, I know for sure the timing chain was. Has there been any cases of the replacements going bad as well?

 

To look at the valves you need to remove the intake manifold not the head. This is a fairly easy thing to do. Maybe an hour of labor.

 

My MINI dealer charged bout $850 for walnut blasting (2 years ago).

Most independent MINI shops are bout $400 for the same.

To inspect it you remove the air box and then the intake which is below the air box. The ports face away from you so you need to use a snake camera or a mirror and flashlight to check the buildup.

Post up what area you are from and someone may be able to tell you of good place for that service

 

I got the same issue with the idling whenever I stopped. I change both O2 Sensors, Camshaft Sensor, Vacuum Pump, cleaned Intake, No CEL, No Code.

However, everytime I the idling starts to gets crazy I did below but I need some advise to analyze it.

The Idling settles down when:

1. I lift the oil dipstick
2. Release the PCV hose
3. Open the Valve cover cap
4. Detached the connector of the Camshaft Sensor
5. turn off the engine and start again (sometimes)

Hope anyone can help me.

Thanks

 

You have a bad PCV valve. The pressure is being released through the openings you are providing. Time to price out a new valve cover before you blow engine/turbo seals.

OP, you may want to try one or two of the above and see if it helps and go the same route.

 

Thanks a lot shreksbrother, by the way my mini just came out from the dealer and can't resolved this issue. The BMW service adsivor said that they test the car with the new PCV or valve cover but runs with the same idling issue (if it's true. It's already a backjob when they change the valve cover gasket only because of oil leak in the cover). This happens when the dealer overfills my mini when they change oil.

However, I agree with your analysis and see how it works.

 

I dont think its the PCV valve because he's not using any oil between changes.

Might be related to the transmission maybe its time for some new atf fluid. With the car in neutral are the revs stable?

 

When in neutral, the revs plays a lot. Almost stalling and then revs up to 2000rpm at the highest sometimes. I didnt mention the oil leak in the cover came up again. The oil leak is like a mist in each of the valve cover screw . I change oil every 10,000km but I didn't have that much oil usage. And btw, as per my service advisor they dont change the transmission oil.

But I also notice one thing again, the air filter pipe connected to the turbo is getting loose, and Im afraid of over-tightening it. Is it also because of the pressure blocked from PCV?

My Mini cooper is jcw 2009. (Manual)

 

Sorry should have replied with a quote.

 

Sorry Guys, replacing Valve Cover doesn't solve the my idling issue....Next move is to replace the SOLV/Vanos and Non return Valve

http://www.ecstuning.com/Search/Site...692/ES2675959/

I Will update you soon as it works.... wish me luck

 

IT WORKS after replacing the Non Return Valve and SOLV......Its my 3rd Day now and it seemed OK idling issues settles down.....however I still noticing some slight playing on idle but not so much, so I might change the Fuel Tank Breather Valve

http://parts.miniofkennesaw.com/prod...537543285.html

Done during when the engine idling is slightly playing
Anyone I need your advise about the Fuel Tank Breather Valve I pulled the breather hose from the PCV or Valve cover and cover the breather hose then it started runs rough like its building up some pressure.

However;

IN NORMAL CONDITION when engine is on idle (idle not playing) when I cover the Breather Hose the idling revs up and get stable.

I read in the other forum that the fuel breather valve can cause this idling because its directly connected to the intake manifold together with the Intake breather hose from PCV.

Regards to all

 

Latest, after changing the fuel tank breather valve purchased from ECSTUNING http://www.ecstuning.com/ES33695/, the idling issue is gone...now running smooth and I have noticed as well the big difference in fuel consumption......Regards to all.

 

Thanks for the update: Here the pic of the item. This is the version for the N14 Cooper S / JCW engines . 13537543285

http://www.ecstuning.com/Search/SiteSearch/13537543285/

 

update..Update..again after experiencing surging during idle again, I fnally decided to replace the Throttle Body...ordered from ECS Tuning great deal https://www.ecstuning.com/Search/Sit...918/ES2587103/....it works. Cleaning TB is just a temporary solution after all...it's the spring that worns out inside not the gears.

new Throttle Body performance after running and stopping to idle; RPM stabilizes from 1200 down to 800 slowly...unlike before when stopping; RPM drops down 500 and bouncing.... Just an observation...

 

Looking inside the Throttle Body.....Just openning it, is way too difficult and definelty sealed, so dont even bother cleaning it. Any cleaning agent will not even reach the gears or the spring....

 

Thanks for the update , glad it worked.