2007 Cooper S Auto. ~23k miles. My car's check engine light went on Fri, Dec 12th. Didn't drive it over the weekend. I brought it into the dealer on Mon, Dec 15th. Oh, tire pressure light went on; got a nail in the rear right tire while driving to the dealer. Turns out there's excessive carbon build-up in the 4th piston, which was causing rough idle upon cold starts. Was supposed to be ready in a few days, then Fri, then Mon, now it won't be ready until Wed the 24th. Anyone else having issue of excessive carbon build-up? Dealer says it's starting to pop up more often. The BMW engineers recommending a thorough cleaning and want to use my car a test subject for a full battery of tests. I only use premium gas at the name stations (Shell and 76). All under warrantly. Love my car, but not sure how much I'd love it if I had to pay for this if it happens again after the warranty is done. Any similar situations out there?

 

Sorry.. didn't read over the site first... looks like there's plenty of talk about this subject already.

https://www.northamericanmotoring.co...-database.html

Thanks.

 

You provided a link to the "cold start issue" database but your carbon buildup and rough idle doesn't necessarily imply the same issue.

 

I add a bottle of Techron fuel system cleaner to the fuel tank every 5000 miles or so and I have not had any rough idle issues so far. Current mileage is 19k miles. The cleaning additives put into premium gas or other grades are usually in very small amounts so they may not prevent carbon build up over time.

 

Techron is good. I am using Swepco 503 in a hot 396 with excellent results.

Water decarboning works well but requires prior knowledge.

 

Techron is good, but BG44K is liquid gold. I plan on adding the latter to my R56 every 7500 miles, like I did with my R53. Nothing beats it (except for maybe Techron's price)

 

I put a container of name brand fuel system cleaner in last weekend and got 36.5mpg for a 250 mile trip that I usually get about 33mpg on. Maybe it adds some cowbell to that gas!

 

How many gallons in that container of fuel system cleaner you put in? I think it has a 93 octane rating...

 

Swepco is great and is recommended in the Porsche circles.

I also have been use Redline SL1 for a quite a while. It is appoved by BMW and is available at the BMW dealer.

 

Our MINI is getting a partial engine rebuild (pistons being replaced) because it's fouled with carbon. Started off as a cylinder misfire code and after replacing many parts without success they think the cause was a leaking valve cover seal. We've been very meticulous with our MINI; performing additional oil changes between the computer based intervals; mostly using top tier 93 octane gas; regularly using a fuel system cleaner.

 

How many miles is on the car? Did you do mostly highway or city driving? What was your oil change interval?

 

BG44K is very good but it is not needed on a regular basis.

Best to use Swepco 503, Techron or Redline SL1 every 1-2,000 miles and use the BG44K only once every 15-20,000 miles. It is hard medicine only necessary to break down existing carbon deposits which an engine should not have when fed a regular diet of the other three.

 

A leaking valve cover seal is not going to cause excessive carbon buildup in the cylinders...........maybe you meant valve stem seal?

I'm curious if any of these cars suffering carbon buildup ever get run hard or for long trips, or just around town? Not accusing mind you, just looking for answers and information..........

 

I started having issues with cold starts last winter. I thought it was the fuel I was using so I experimented with different fuels (87, 89, 91, 92) and I was still having the cold start issue. I bought a can of 44K and I have not had the cold start issue since. I use 44K every 5000 miles and every fill-up I install a bottle of BG Supercharge II into the tank. Supercharge II is suppose to help prevent the build up of carbon on engine parts. I also just recently used BG Quick Clean and BG MOA (Motor Oil Additive) during my last oil change. I also purchased a can of BG CF5 for my wifes G6 GT. CF5 is not as strong as 44K, but is a little stronger than Supercharge II. I am a big believer in the BG products. Everyone in my family uses it and has never had any issues. I have only heard positive comments about BG. It does help in engine performance and fuel mileage. Take a look at their website and see for yourself. www.bgprod.com. BG is excellent stuff.

 

Thanks for the replies. Looks like I'll have to start using these oil additives every 5k miles. Hopefully that does the trick and prevents this in the future.

Just came back form the dealer to get some stuff out of the car. They were not very helpful. I think they will end up missing their Wed the 24th completion deadline. I'm getting really irritated. No loaner car offered, nothing.

A same day check-up turns into a minimum 10 days in the shop and all I get is, we're gonna keep your car and use it as a tester to try and diagnose the problem for future cars. The BMW techs say it's a fuel quality issue. C'mon. I use the highest grade possible here, the 91 from Shell and Unocal76. I park inside, don't drive particularly hard, the weather in CA is good, and follow all the maintenance rules put forth by MINI. It's only got 23k miles on it.

Hey, I should be compensated for letting them use my car as a guinea pig and the incredible inconvenience of not having my car for at least 10 days. Am I getting a little too worked up over nothing here?

 

Oil additives have absolutely nothing to do with this issue, it's probably fuel, just like they say - or driving conditions...........

Did they give you a loaner? If so I'd let them use your car till they're happy with it - you'll get a better result too.

 

No loaner given or offered. What's wrong with the fuel? I use the 91 octane from Shell or 76. It's the highest grade they have in CA. Could it be that special CA blend, then why aren't there 10k other MINI owners in CA suffering from this issue? I live in the San Jose area. The weather is pretty mild all year. We don't get 4 seasons here. I have an easy, no traffic, 20 mile commute to work and I drive fairly conservative for a Cooper S owner. The more I think about it, the more pissed I get. I love the car, but the dealer has to treat me right.

 

I think you are right to be PO'ed at not being offered a loaner.

 

Approx 37K miles on the odo (14 months). Mixed driving, mostly highway commuting miles. No towing, track or other HTHS use. So far the MINI computer has indicated an oil/filter change at 18K and 37K miles. I have actually changed the oil/filter at 2K, 11K, 18K, and 26K. The car passed a MINI scope inspection service at 30K miles without issues. I have no idea what actually caused the carbon buildup. The valve cover leak was what the service writer told me. Apparently this was a big deal because they had a MINI technician come down to take a look at it. I'm not sure even MINI knows what is causing the carbon buildup. The car has been at the dealer 2 weeks and still counting. But we can't complain, we've had a MCS loaner the entire time.

 

Someone sent me a link to this thread because I had the identical problem. A couple of weeks ago we put my wife's '07 MCS w/ automatic transmission in for its first scheduled service. About the middle of last week we finally got it back. After they finished the regular maintenance, they discovered a misfire. They called & wanted to charge about $400 to clean the carbon out of the intake side of the head. They blamed it on "bad gas", and, therefore, I was responsible. We keep all of our receipts, and I was able to show that we had burned only name brand premium from day one. (starting to sound familiar?) I maintained my temper, but for the next few days I'm sure I wasn't their favorite customer. They agreed to fix it for free ("one time good will"), and my wife had a free loaner to drive. But, they would never admit that it was a MINI problem. Their logic seemed to be "It's not the coils or sparkplugs, therefore it must be bad fuel." After we picked it up, I read the repair sheet. The deposits were found in the #4 intake. (even MORE familiar?) To me this screams out "mechanical problem". Or, I suppose we could assume all the "bad gas" went to #4, while #1, #2, & #3 got the good gas.
Corporate MINI really needs to look at this. When I went to MINIUSA they refered me back to the local dealership. This accomplished nothing. The local dealership is locked in on their "bad gas" stand. They say they've seen this in other '07+ MCSs....all were "bad gas" problems. I asked if they had seen this in the pre-'07s MCSs, & evidently they haven't. This again screams out "mechanical problem."
How can we get someone above local level envolved? Do we have to go to England.....or Germany?
HHH

 

Hope this doesn't become a major problem with more and more cars down the road...

 

Yah, the "bad gas" excuse is a total joke. Looks like our MINIs have the same defect. It's a design problem or a poor quality assurance thing at the factory. This kind of issue at only 23k miles is ridiculous.

 

When I went to the dealer on Sat, the SA said that if the carbon buildup ever reoccurred he said they would cover it. I emailed him back later when I got home and wanted him to explicitly write that into my maintenance record, because I don't want to have to argue about this issue again 1 day/1mile past my warranty and they start charging $400+ for cleaning (their mess). Of course, no reply.

 

We need to get a list of all '07 MCS owners who have experienced (or are experiencing) this problem & present it to MINI/BMW......kind of like a "class action request" that they address it. There's power in numbers. As long as we're all divided up at the various dealerships around the country, it's doubtful that anything will happen.

HHH

 

Yes it's a problem - I've had my early '07-build R56 in & the same thing was diagnosed after 35+K miles. It's not the gas; I've used BP Gold 93-octane 99.9% of the miles I've driven since taking delivery in April of '07.

There's a redesigned cam cover that's supposed to resolve the engine ventilation issue. Mine's wearing it currently, but it hasn't resolved recurrent the cold-start problem...

I was astounded to see how much carbon was inside my S's cylinders the day I stopped into the dealership a month or so ago; at least 1/4" on all four pistons, a nice clean spot where the direct-injection sprays fuel onto the piston heads. My head was sent out at the time for "cleaning" & was put back onto the block after the carbon inside was manually removed.