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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Mon, Jul-17-2017, 07:12:31 PM   #1
shane82388
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Default Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

The other day I was driving to work in my 2003 M3 and was about to get on the freeway and then my car started stuttering and shaking and felt like it was going to stall, but it somehow didn’t. (Check engine light on.) I was able to turn around and limp home with little power or ability to get going very fast.

I’ve started trying to diagnose WTF is going on with it, but I don’t know where to start.

The codes its throwing are misfires on various cylinders and random misfires.

P0300
P0304
P0303
P0305
P0302
P1341
etc.

Everything was running pretty great until the other day, where do you think I should focus my search?

I started with cleaning the MAF and that didn’t do anything at all…it runs rough either way. I even tried unplugging it and it didn’t have an effect.

Vacuum leak? (I checked hoses visually after taking out the covers and airbox, etc and didn’t see anything that looks damaged or even aged and brittle. I tried spraying some soapy water around the intake but no reaction in the idle anywhere when I sprayed it.)

Maybe a sensor of some kind?

Maybe something else?


Thanks for any suggestions, I seriously need them. :-)

VIDEO:https://www.youtube.com/embed/G23FXDtZ4NQ sorta sounds like a diesel right now.
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Old Mon, Jul-17-2017, 07:23:30 PM   #2
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Default Re: Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

I'd look at the coils and spark plugs first.
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Old Mon, Jul-17-2017, 07:26:26 PM   #3
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Default Re: Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

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Originally Posted by figurefive View Post
I'd look at the coils and spark plugs first.
I would assume that too if it was a persistent code, but it changes cylinder literally every time I clear them and turn the car on again, which makes it highly unlikely every single cylinder coil/plug went bad at once I would think...?

I just did the coils on my girlfriends e90 which had a very similar sound/misfire (no check engine) and it definitely was the bad coil, but it was consistently that coil and the code followed it when i moved it to a different spark plug and back, etc.
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Old Mon, Jul-17-2017, 07:33:50 PM   #4
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Default Re: Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

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Originally Posted by figurefive View Post
I'd look at the coils and spark plugs first.
Start here, HF sells a $4 tool that will test coils and spark plugs. Or just pull one at a time and see if that makes it smoother.

Since you think you maf is alright, and assuming your coils and plugs are fine the next step would be fuel related.

How many miles? Original fuel pump?
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Old Mon, Jul-17-2017, 08:03:19 PM   #5
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Default Re: Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

Those look to be all misfire codes. Maybe your FPR shit the bed and fuel is dumping in unregulated. Check fuel pressure.
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Old Mon, Jul-17-2017, 08:03:51 PM   #6
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Default Re: Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

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Originally Posted by poms302 View Post
Start here, HF sells a $4 tool that will test coils and spark plugs. Or just pull one at a time and see if that makes it smoother.

Since you think you maf is alright, and assuming your coils and plugs are fine the next step would be fuel related.

How many miles? Original fuel pump?
Do you have a link to that?

Around 124,000 miles. I don't actually know if it's the original fuel pump or not...but I know I haven't changed it and Ive owned the car for a few years.
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Old Mon, Jul-17-2017, 09:15:01 PM   #7
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Default Re: Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

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Originally Posted by PITT M3 RR View Post
Those look to be all misfire codes. Maybe your FPR shit the bed and fuel is dumping in unregulated. Check fuel pressure.
Okay, how would I go about doing that?
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Old Mon, Jul-17-2017, 09:50:55 PM   #8
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Default Re: Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

There is a Schrader valve under the car on the fuel pressure regulator that is attached to the fuel filter. That's where you attach the fuel pressure gauge. AutoZone should have a kit for around $12.99 or thereabouts. When you're under the car, youll have to remove a cover over the fuel filter/fuel pressure regulator to see it.

Also, check your grounds and your power cables to make sure they're tight and not corroded…. There is a ground strap that comes from under the valve cover over the exhaust headers, that bolts to the head… Make sure that it's tight also. Also the main engine strap is on the passenger side motor mount to the frame, check that too.

Lastly if you have a voltmeter, see what your output is at Idle...These cars to wack ass shit when they don't have the correct voltage being fed
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Old Mon, Jul-17-2017, 10:09:30 PM   #9
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Default Re: Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

Still try the coils first. They can throw all sorts of additional misfires when they go.
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Old Tue, Jul-18-2017, 12:15:09 AM   #10
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Default Re: Almost Stalled, Shuddering, Rough Idle, Multiple Random Misfires

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Originally Posted by shane82388 View Post
Okay, how would I go about doing that?
^^^With the fuel pressure gauge attached to the schrader valve, pull the vacuum line with the car running. With everything working properly you should see 5bar pressure.

No idea how to test other than that, maybe someone else does.

Take one coil and plug out at a time, plug it into this and you can narrow it down.
https://m.harborfreight.com/in-line-...ker-69014.html


For fuel pump test: With the pressure gauge on the schrader valve put the key to position II. You should see 5bar or ~70psi, it should hold for twenty minutes. You can lose no more than .5 bar to pass.

If it doesn't, you have to clamp the lines so you're isolating just the pump. I can't remember but I think I clamped the supply after the filter and the return. Run test again, if you see more than a .5 bar drop in twenty min then it's the pump.

If that passes you can also test the injector side by isolating the clamp.
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Discussing Just had inspection service, no valves needed to be re-shimmed, is this normal or OK? in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)