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7 Series - E65 / E66 (2002 - 2008)
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  #1  
Old 09-12-2014, 09:18 AM
edeskimo edeskimo is offline
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Really rough running of car after gas refills on 2007 750i

I've owned a 7-series since 2009 but recently started having some difficulty after gas refills but it is very intermittent.

It first happened in late spring with very rough starts and the car would rev up and down for awhile and it smelled like unburned gas was coming out of the exhaust. After a minute it would settle down and run okay. This was after a refill of a 1/2 empty tank.

I refilled at a different station next time and no problem.

The next time I went back to the first station again and it was even worse but this time it was a refill from close to empty. The vehicle really, really shook when it ran but luckily I only half-filled it this time because the gas pump was malfunctioning. So I drove it about a mile to another gas stations and filled it up with Super Premium (Octane 95 I think) and immediately the problem settled.

I then thought maybe the problem was the gas station having some sort of pump malfunctions that was causing non-premium gas to come out (I had been using this station for years so it's not that I'm unfamiliar with their pumps and accidentally putting in the wrong gas).

So I stopped using the first gas station and the next 4 months, no problems.

But yesterday I did another re-fill with the new gas station I have been using (different company from the first one) and again quite a rough start, rough and the car shakes a bit when I go above 50 mph. The problem persisted for my whole drive to work and the check engine light was on.

I phoned my local mechanic and have an appointment to have it checked out on Tuesday. He thinks it may have something to do with some kind of an evap valve but I wonder if some sort of sensor is malfunctioning in the vehicle. I mean why would the problem recur from using an entirely different brand of gasoline and why would the problem go away with addition of the super-premium previously. I don't have room in the tank right now to see if the super-premium correction works again.

Anyhow, I was just wondering if any of you had run into similar problems or have guesses as to what may be happening here.

BTW, my engine was fully rebuild at about 140, 000 miles and I have only put about 8000 miles on since the rebuild and outside of these issues with the gas re-fills it has really run perfectly.

Thanks in advance.
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  #2  
Old 09-12-2014, 08:01 PM
dvanlare dvanlare is online now
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BMW recommends you always use top tier gasoline. Make sure your gas station is on this list.

http://www.toptiergas.com/retailers.html
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  #3  
Old 09-13-2014, 06:57 AM
edeskimo edeskimo is offline
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Quote:
Originally Posted by dvanlare View Post
BMW recommends you always use top tier gasoline. Make sure your gas station is on this list.

http://www.toptiergas.com/retailers.html
I've been using Shell and Esso which are both on that list but thanks for pointing this out.
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  #4  
Old 09-13-2014, 07:49 PM
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First_745Li First_745Li is offline
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Yes but it should be premium octane not regular octane.


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  #5  
Old 09-14-2014, 01:27 AM
irish745 irish745 is online now
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Sounds to me like some prob with the evap or tank vent valve

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  #6  
Old 09-14-2014, 06:24 AM
edeskimo edeskimo is offline
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Quote:
Originally Posted by First_745Li View Post
Yes but it should be premium octane not regular octane.


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I have only ever used premium gas. I have had a 7 series for 5 years without this problem.
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Old 09-14-2014, 06:36 AM
luigi524td luigi524td is offline
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I suspect the problem may be a fuel supply problem created by a filling station that failed to properly maintain its equipment (tanks and filters). The resulting issues may have been temporarily remedied by a fill of proper gasoline (cleanliness - not octane) but there may have been left behind an assortment of debris, water, etc etc in your car's filters. Normally they can handle quite a bit so you might try a dose or two of Chevron Techron fuel system cleaner in your gas tank to see if it'll help. In the meantime I'd put the gas station on notice that they should check their equipment (pumps, filters, tanks) for a problem.

You might not be the only driver experiencing this issue.
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  #8  
Old 09-14-2014, 08:16 AM
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First_745Li First_745Li is offline
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IDR from your original post, have you changed fuel filter yet? That might be something to look at also.


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  #9  
Old 09-14-2014, 02:18 PM
edeskimo edeskimo is offline
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Quote:
Originally Posted by luigi524td View Post
I suspect the problem may be a fuel supply problem created by a filling station that failed to properly maintain its equipment (tanks and filters). The resulting issues may have been temporarily remedied by a fill of proper gasoline (cleanliness - not octane) but there may have been left behind an assortment of debris, water, etc etc in your car's filters. Normally they can handle quite a bit so you might try a dose or two of Chevron Techron fuel system cleaner in your gas tank to see if it'll help. In the meantime I'd put the gas station on notice that they should check their equipment (pumps, filters, tanks) for a problem.

You might not be the only driver experiencing this issue.
That is what I thought with the first station. So I changed stations and the problem went away for 3 months before returning again at the new station.

I suppose borh stations could be messed up but I think it seems more likely somethong goes intermittently wrong with the car.

The farther I have driven since thw refill the smoother the car runs but it still isn't back to normal.

I will give your suggestion a try, though.
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  #10  
Old 09-14-2014, 02:20 PM
edeskimo edeskimo is offline
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Quote:
Originally Posted by First_745Li View Post
IDR from your original post, have you changed fuel filter yet? That might be something to look at also.


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The whole engine was rebuilt in December. Would it have been done then?
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  #11  
Old 09-14-2014, 06:04 PM
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First_745Li First_745Li is offline
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No it's not part of the engine. It's under the car left side.


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  #12  
Old 09-17-2014, 11:13 AM
edeskimo edeskimo is offline
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I took it into the mechanic yesterday for assessment.

He checked the codes and apparently the issue was cylinder 2 was misfiring. He said about 95% of the time that is due to ignition coils or spark plugs malfunctioning. Now the spark plugs are new as of December so he thought it was probably the ignition coil. So the problem this time had nothing to do with the gas and coming up after the refill this time was just a coincidence. I do suspect the first gas station was supplying some sort of defective version of premium and the way the engine ran back then is quite a bit different then the problem I have now. I only thought they might be related since the rough running always seemed to occur after refills. They did check the evap valve and it is functioning normally.

Anyway, he switched the ignition coil from cylinder 2 with the one on cylinder 1 to see what happened. Interestingly, the misfiring problem went away. If it is the ignition coil he said the problem will come back but this time on cylinder 1 instead of cylinder 2 now that they have been swapped. If it comes back on cylinder 2 again he said he would have to further investigate since something unusual would be happening.

I drove it home and back to work today and the car is running absolutely normal again. So at this point he has told me just to continue to drive and see what happens.

He did tell me that if they change 1 ignition coil they usually just change them all and mine are still all originals as they were not changed during the engine rebuild.
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