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645ci hesitation

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Hey guys.... wondering if any of you have had this issue and waht may be happening. When i drive at asteady 38 ish MPH, it seems like someone is lightly tapping the brake every three seconds.... when i look at the tach and speedo there is no change..... car does nt slow down at all but you can feel a slight hesitation........ I wonder if its kicking in and out of overdrive at that spped ?
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I had the exact same problem. But I was never able to find a solution or reason. Sold the car 3 months ago.
Do you have any codes?

and is your idle smooth?
Sounds like a possible coil pack problem, or possibly a clogging fuel filter. Check all of your coil packs to make sure they are seated properly. You could also remove the COP wires one at a time, to see if you can find the cylinder that is having a problem. One other thing you could do is to run a big bottle of Techron fuel supplement in the fuel tank. It will help remove any carbon or trash in the fuel system, that might be a problem.


Hope this helps!
Thanks guys. It only does it at that speed. No codes. smooth idle
I have that same problem, I'll let you know what I find out and if you would do the same.
I had roughly the same problem just not as bad. I finally noticed it when I was in manual shift. Its 5th gear (about 36mph). It kicks in and out real fast on my car and gives me a hesitation and kind of a mild bang. If I drive the car hard for about a week its fine for like a month and then it comes back. No one has found a solution for it. This might not be anything like yours but I home that it helps
5th gear (about 36mph),
I'm still in 2nd gear at 36 mph, lol
Mine will normally shift into 5th gear under light driving going mid 30's. The problem always happens on this one road that I go on so I wanted to see that gear I was actually in cruising on this road. When I switched over to manual gear shift I put it down a gear so that you can see what gear you were in and then put it back into the original gear. That is why I said 5th gear obviously it depends on how hard you are on the throttle and how long you have been cruising on that road as to what gear you will be in. It seems like the computer is hesitating what gear that it should be in ( because it shouldn't be in 5th at 30+) and keeps switching back and forward between gears as the presser builds up on the gears. That is just my take on it
Thanks, I'll try that test, but that seems to be what mine is doing.....
This is starting to sound like you need to retrain your transmission. There is thread showing how to reset it, without taking it to the dealer. It should be very easy to find, since it pops up frequently. Your 1st thread made it sound like your engine was jerking, while under load?

Good Luck!
Steady 38 mph , no load
I did the transmission reset when I bought the vehicle just so that it would learn how I drive. It did work for a while but honestly at the time I was not familiar much with the problem I only noticed it once or twice. I might try to reset it again since it was so easy.
I tried the transmission reset and it didn't work so I just replaced the spark plugs and coils so I will update in a few hours. The replace brake light is still on does anybody know how to reset that?
i'm having the same problem at about 35-40mph had the tranmission reset i guess thats what they said so that i could retrain the transmission afterwards it lasted 2 days and went back to doing the same thing, now i my SES light is on and an initial message "increased emmissions"...anyone had that problem, I checked my gas cap alos.
Transmission can't decide between 5th & 6th gears around 40mph

I recently purchased a 05' 645 coupe with 60k on it. Mine had the same "can't decide if it wants to be in 5th or 6th gear while cruising on a level road between 37 and 42 mph (which 40mph is the prevalent speed limit around where I live). I tried the transmission retraining and it would only last a short while. I was going over the car checking routine items being a new to me vehicle and noticed the air filter was dirty. I changed the air filter and the shifting problem went away. It now runs and shifts smoothly.:)
I really hope that it is that easy. Thats the one time that I would love to feel stupid. I am away from my car for about a month so if someone else tries it can you post the results
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