I have a 2006 non-S Cooper convertible with 80K miles and manual transmission. For the past 6 months or so, I've been having an issue where the engine stumbles and sometimes stalls on idle during the first few minutes after filling up. Typical scenario: I pull into a gas station after driving 30-60 minutes. It has been running fine and of course totally warmed up. I fill up, and pulling out of the gas station, the engine is stumbling at idle. After a few minutes, the engine is fine again. Just last night, I pulled out of the gas station and the engine stalled while waiting at a red light. Went 100 yards, stopped at another red light and engine stalled again. Went on and engine was fine for the remainder of the trip. Sometimes it stalls while I'm still maneuvering around the gas station, but it always goes back to running fine within a couple of minutes. Any ideas about what's happening?
I'd think if it was a clogged breather it would happen before the fill up. As the fuel was used it would starve for fuel. Had this happen on another car. If it was that when the cap was opened the pressure would equalize & run fine until it built up pressure again. Does the tank go woosh when you remove the cap?
After the initial shut off, sometimes I squeeze the handle until it clicks again, but I don't make a special effort to top off like pulling the nozzle out partly. It doesn't whoosh when I take the cap off. Some of my previous cars did that but I haven't noticed it on the MINI. Next time I take the car out, I'll try just opening/closing the cap at the end of the trip and seeing what happens if I restart the car. If it stumbles, it's related to the tank pressure. If it doesn't happen, the problem is caused by something else.
I top mine off when I fill up and get every last drop in I can. I know you are not supposed to but I have never had a problem. It may have to do with the breather but you could also be getting bad or watered down fuel. Try adding a bottle of Chevron Techtron for a 20 gallon tank and fill you next take with 93 octane fuel from Shell or Sunoco. Maybe you have varnish built up in the fuel system that needs to be cleaned out. It may take 2 or more tanks of 93 and techtron to clean everything up. It could also be a MAP or T-MAP sensor going bad but try the fuel treatments first since they are the cheapest and you always need fuel. One more thing it could be is an O2 sensor since everything is warmed up and you shut off the car. When the ECU resets the O2 is already warmed up and it's trying to adjust everything which could cause what you are feeling. That did happen to me before and after I checked everything I replaced the O2 everything was right again. Good luck let us know how you make out.
Yes if you keep clicking to get to the next even dollar. Letting it click one more time is not going to harm anything. At least that has been my experience. Your mileage may vary.
I'm embarrassed to admit that after all these years, I still don't have a code reader. This might give me motivation to set up a smartphone app with OBD bluetooth adapter. However, the symptom is simply rough idling that goes away after a couple of minutes with no warning lights, and I'm not sure that would trigger any codes. Those are interesting ideas. Unfortunately 93 octane is very rare around here and it is far out of my way to obtain it.
I top off too, have not had a problem when doing so. Last fill was darn close to 14 gallons in the supposed 13 gallon tank.
I've been guilty of adding 14 gallons to the 13 gallon tank as well. No problems with it. However in the Jeep, if you fill it to the top of the neck, you better be burning it off fairly quick... It sets off a gas cap warning, and will keep it on until you shoot the inside of the cap with some WD-40.
Is the tank on the red light close to empty? I used to get something like this with the Subaru. I figured either there was something in the tank or air got sucked up? So I filled up on 1/4 tank to fix the issue.
So, I'm finally hopeful for a resolution after suffering with this for months. The issue was getting much worse. Stalling at idle also began to happen regularly during the first 10 minutes after starting out. It would be usually okay after the engine warmed up. But bizarrely, the worst situation was after filling up. I might have been driving an hour, and then stall several times just trying to pull away from the pump and out of the gas station. I took it to a respected MINI shop and they identified a major issue with the engine (I'll write about this later). After repairs, the engine runs better than it had in a long time. The idle stalling is almost gone but not completely. However, the stalling after fillup was not affected at all. Without fail, it stalls after filling up and I have trouble for the first few minutes of driving. I finally had a clue this weekend. The filler cap warning light went on briefly. This could explain the behavior, if the gasket wasn't sealing completely but did seal after enough pressure built up in the tank. I have a replacement cap on order and should receive it by tomorrow. Really, really hoping this simple fix will do it.
Hopefully the gas cap does it... Kinda wonder if the "purge valve"...not sure the technical name...but it helps to draw a vacuum on the tank is bad...maybe letting fuel get sucked into places it should not be going...the MINI part is $$$..but I remember reading that it is actually a generic part used on MANY cars....just happens to be sold by MINI, but not cross referenced by non-MINI parts places as fitting...... If the cap does not do it for ya..let me know...I'll look for the lthread over on NAM.
Unfortunately, the new gas cap didn't fix it. In addition to the fill up scenario when it stalls every time, I also have a cold engine scenario during the first 15 minutes where it may stall during idle, but not consistently. It will idle normally for awhile, then the rpm might suddenly dip sharply and the engine may recover by itself or it may stall. It's almost like there was a very brief interruption of fuel. My repair shop thinks it might be the fuel pump. They plan to hook up a fuel pressure gauge and watch what happens when it stalls. I guess MINI calls it a "fuel tank breather valve". I'll mention it to the shop. RealOEM.com * BMW R52 Cooper FUEL TANK BREATHER VALVE