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      08-21-2014, 07:00 PM   #1
LeftLane335
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Irregular RPM and car shaking

So yesterday my 2008 335i started to experience a flutter in the RPM ( it goes up and down when at idle, sometimes reaching nearly 2500 RPM). On top of that, the car shakes when at low RPM and there is a very noticeable power drop. All of these symptoms started simultaneously. I got it diagnosed and got codes PO300, PO303, and PO304 and was told that cylinders 3,4, and 6 had misfires. The first thing I assumed was that the fuel pump had gone bad, however, that was not the case. At the dealership I was told that the pump was good and that the problems might be the injectors.

Now...... before I go spend $600 dollars on spark plugs, is there any possibility that the misfires are due to bad spark plugs? or maybe the boots on the plugs?

Help Pleaseeeee,
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      08-21-2014, 09:13 PM   #2
este
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its possible whens the last time you changed them? you could also try moving the coils around and see if the misfire moves with it which would mean its the coil.
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      08-21-2014, 09:20 PM   #3
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Spark plugs aren't $600. They're like $100 and it's probably one of the easiest DIYs. If you have no idea what you're doing, just follow the instructions from one of the many DIYs floating around out there and it'll probably take you an hour. I've actually done it in 20 minutes on my car.
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      08-21-2014, 09:36 PM   #4
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Quote:
Originally Posted by atinybug View Post
Spark plugs aren't $600. They're like $100 and it's probably one of the easiest DIYs. If you have no idea what you're doing, just follow the instructions from one of the many DIYs floating around out there and it'll probably take you an hour. I've actually done it in 20 minutes on my car.
I think he meant injectors for $600. But yes op, the misfires could be from either bad coils or spark plugs. Swap the coils around and see if the misfires move around. If they don't then inspect the plugs and if they look good the it's most likely your injectors.
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      08-21-2014, 09:36 PM   #5
e92_enthusiast_1
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He meant before he spends $600 on new injectors so it was a little confusing. My suggestion though. Siwtch the plug and coil from a known bad cylinder in two different known good ones and see where the code follows. If it doesnt go anywhere then yeah its probably the injector.

Quote:
Originally Posted by atinybug View Post
Spark plugs aren't $600. They're like $100 and it's probably one of the easiest DIYs. If you have no idea what you're doing, just follow the instructions from one of the many DIYs floating around out there and it'll probably take you an hour. I've actually done it in 20 minutes on my car.
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      08-21-2014, 10:02 PM   #6
LeftLane335
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Quote:
Originally Posted by atinybug View Post
Spark plugs aren't $600. They're like $100 and it's probably one of the easiest DIYs. If you have no idea what you're doing, just follow the instructions from one of the many DIYs floating around out there and it'll probably take you an hour. I've actually done it in 20 minutes on my car.
Yea sorry, i meant the injectors not the spark plugs.
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      08-21-2014, 10:20 PM   #7
bransan
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Was it running normally, then all of a sudden started running rough?
Sounds like a possible vanos problem. Valve timing? I have had my car do that for a few minutes then snaped out of it. My scanner said misfire and cam timing on #1 bank. I'm going to try rebuilding the Vanos. Sounds like a very simple repair. Good luck
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      08-22-2014, 06:10 AM   #8
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Could be carbon issue as well
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