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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, 02:58:09 PM   #1
Mr Wiggles
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Default Rough idle, misfire all cylinders, ignition timing off, RPM dependent

I have an '06 M3 with 120k miles on it that has been idling very roughly and getting misfire codes on all cylinders as well as a random misfire code. I started working at an indy BMW shop recently and have access to their Autologic (ugh, so nice) and the timing is super off on all cylinders at idle, like 1-5 milliseconds. The mistiming gets better as the RPMs go up, and is generally pretty ok at about 5k and above (100-200 microseconds). The misfire counter steadily goes up on all cylinders at idle, though 1, 3, and 4 have the most, and the misfires happen way less frequently after 3k or so RPM. I've been having VANOS issues since I got the car (a year and 5k miles ago) but those I'm pretty sure are completely electrical (bad connection) and unrelated to the misfire codes.

Any thoughts about what might be causing this?
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Old Mon, Jul-17-2017, 03:06:49 PM   #2
Drewster
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Default Re: Rough idle, misfire all cylinders, ignition timing off, RPM dependent

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Originally Posted by Mr Wiggles View Post
I've been having VANOS issues since I got the car (a year and 5k miles ago) but those I'm pretty sure are completely electrical (bad connection) and unrelated to the misfire codes.

Any thoughts about what might be causing this?
Start with the Vanos issues you know you have, and *then* track down the misfires. If it turns out a rat chewed through a ground on the main wiring harness, then there ya go!

Doesn't make sense to track down something that could be about 10 different things, when there's something that's possibly related and relatively straightforward to diagnose.

What did the Autologic tool show for the Vanos test?
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Old Mon, Jul-17-2017, 03:14:56 PM   #3
Mr Wiggles
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Default Re: Rough idle, misfire all cylinders, ignition timing off, RPM dependent

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Originally Posted by Drewster View Post
Start with the Vanos issues you know you have, and *then* track down the misfires. If it turns out a rat chewed through a ground on the main wiring harness, then there ya go!

Doesn't make sense to track down something that could be about 10 different things, when there's something that's possibly related and relatively straightforward to diagnose.

What did the Autologic tool show for the Vanos test?
It went through the VANOS test just fine recently (a week or so ago, probably drove it 10 miles since then). I'm pretty sure the VANOS codes (open circuit on intake and exhaust and associated timing over-advanced/retarded) are unrelated because they've been around for a long time without misfires. I'm kind of wondering if maybe the last gas station I went to switched up the fuel in their tanks (I always put in 93 octane). Maybe it's a fuel filter issue? Dunno.

I thought it might have been the oil separator and it's possibly it still is, but I don't think the VANOS issue is causing this. 1) because it's been around for 5k miles without the misfires and 2) because VANOS isn't activating, and yet the misfires still decrease in frequency as RPMs increase. Also I can clear the VANOS codes and the car will re-incorporate VANOS at least temporarily, but the misfire is still there as bad as ever.
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Old Mon, Jul-17-2017, 03:28:31 PM   #4
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Default Re: Rough idle, misfire all cylinders, ignition timing off, RPM dependent

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Originally Posted by Mr Wiggles View Post
It went through the VANOS test just fine recently (a week or so ago, probably drove it 10 miles since then). I'm pretty sure the VANOS codes (open circuit on intake and exhaust and associated timing over-advanced/retarded) are unrelated because they've been around for a long time without misfires. I'm kind of wondering if maybe the last gas station I went to switched up the fuel in their tanks (I always put in 93 octane). Maybe it's a fuel filter issue? Dunno.

I thought it might have been the oil separator and it's possibly it still is, but I don't think the VANOS issue is causing this. 1) because it's been around for 5k miles without the misfires and 2) because VANOS isn't activating, and yet the misfires still decrease in frequency as RPMs increase. Also I can clear the VANOS codes and the car will re-incorporate VANOS at least temporarily, but the misfire is still there as bad as ever.
If you're seeing those codes while the car is misfiring, you can't rule out Vanos. If there is a Vanos fault, the cams are left in the position they were at when the fault occurred. If the codes popped up at high RPM, the car running like ass at low RPM is totally expected.
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Old Mon, Jul-17-2017, 03:29:54 PM   #5
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Default Re: Rough idle, misfire all cylinders, ignition timing off, RPM dependent

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Originally Posted by Drewster View Post
If you're seeing those codes while the car is misfiring, you can't rule out Vanos. If there is a Vanos fault, the cams are left in the position they were at when the fault occurred. If the codes popped up at high RPM, the car running like ass at low RPM is totally expected.
They don't pop up at high RPM though, they pretty much always show up when the car starts, so basically at idle.
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Old Mon, Jul-17-2017, 03:40:17 PM   #6
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Default Re: Rough idle, misfire all cylinders, ignition timing off, RPM dependent

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They don't pop up at high RPM though, they pretty much always show up when the car starts, so basically at idle.
If you're experiencing Vanos connectivity issues and misfires, I would check your harnesses, grounds, and verify their connectivity back to the DME.

For misfires at idle in general, I would check MAF(how does it run with MAF unplugged)/ smoke test, FPR vacuum connection, ohm out coils, and check/ replace plugs.

^That's my advice if you want to just ignore the glaring warning from your DME on why it's pissed
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Old Mon, Jul-17-2017, 03:41:42 PM   #7
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Default Re: Rough idle, misfire all cylinders, ignition timing off, RPM dependent

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Originally Posted by Drewster View Post
If you're experiencing Vanos connectivity issues and misfires, I would check your harnesses, grounds, and verify their connectivity back to the DME.

For misfires at idle in general, I would check MAF(how does it run with MAF unplugged)/ smoke test, FPR vacuum connection, ohm out coils, and check/ replace plugs.

^That's my advice if you want to just ignore the glaring warning from your DME on why it's pissed
Ok, thanks for the suggestions.
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Old Mon, Jul-17-2017, 03:50:22 PM   #8
Steve M3
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Default Re: Rough idle, misfire all cylinders, ignition timing off, RPM dependent

When is the last time you changed the plugs and coils?
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Old Mon, Jul-17-2017, 04:03:36 PM   #9
Mr Wiggles
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Default Re: Rough idle, misfire all cylinders, ignition timing off, RPM dependent

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When is the last time you changed the plugs and coils?
Never (since I bought it at 114k miles). There are no coil codes, but I did recently buy new plugs. Since I have access to a shop I'm probably going to make a day of it and take off the whole valve cover and really try to clean things out, adjust valve clearances, etc., and will change the plugs then. Should probably get to it in the next week or two.

Last edited by Mr Wiggles; Mon, Jul-17-2017 at 05:44:48 PM.
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Old Fri, Jul-21-2017, 01:20:44 AM   #10
Mr Wiggles
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Default Re: Rough idle, misfire all cylinders, ignition timing off, RPM dependent

Has anyone seen my hat? Oh here it is, in my hand...

So yeah, it was the VANOS connector after all. I pushed on the connector while it was idling roughly and it made some sort of weird ticking sound for half a second and then went back to idling normally. It comes back every few miles or so but goes away again if I press on the connector. If it's illuminating to anyone, it's the part of the connector closer to the engine that seems to be causing the misfiring. Still not sure why.
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Discussing Rough idle, misfire all cylinders, ignition timing off, RPM dependent 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)