[Craig]

Hi guys,
I bought my E92 with 44k miles. The car has always done this at cold start-up. It has a miss or skip that is audible. Even my wife asked me about it! "What's wrong with your car?" It's much easier to hear in person than when recorded on an iPhone. The car may do it all the time at warm idle too but I just can't hear it, probably because it's quieter when warmed up.

In the video the miss begins at about .42 seconds and continues irregularly.

Otherwise the car runs smooth and strong. No codes show. No CEL on.

Coil? I think it's ignition related but I don't know what's causing it?

http://www.youtube.com/watch?v=JxQ15cAKLTg

[beakmoney]

In for the answer. Mine does the same thing. No cel, no other running issues so its not a concern really.

[b1aze]

Mine also does this and even more since i got the new injector model installed. Brought it to the dealer and they said its perfectly normal and they cant do anything about it. No CEL, codes, etc. The tech (who i trust) says it doesn't even register as a single misfire according to the scanner they use. Once the oil is warmer (>100*f) it doesnt happen at all.

[najin23]

n54 DI is doing that naturally. There's no problem. Now, I did change my plugs to NGK cloer gapped than the factory, and idle became much smoother. I think they are just numbers of small misfires maybe, and closer gapped plugs seemed to fix that.

[Craig]

Okay. Well, those responses atleast make me feel a little better that other N54s do the same thing. So maybe I don't have to diagnose further. :-)

Anyone else have the misfire sound at cold idle start-up?

[rays 335i]

mines will only on e85 mix too high.. for less than a minute

[lenn]

Mine did this at 48k miles. Took it into the dealer and insisted (over the course of 5 days) them inspect the injectors and fuel pump. They replaced all 6 injectors and ran a boroscope through the intake to find a fair (not terrible) amount of build up on the intake valves.

The injector replacement alone did not fix the hiccup. 2 weekends later I cleaned the intake valves and got rid of the idle hiccup. Mine was doing it both cold and warmed up. Every 15-30 seconds the exhaust would miss and "puff" a little. It was easy to spot on cold mornings by watching the steady stream of exhaust condensation/smoke get disrupted by the miss.

I could feel the miss/hiccup most obviously in the shifter and clutch. My wife was able to feel it in the passenger seat too.

long story short. Clean your intake valves.

[najin23]

How did you clean yours?
Believe me, my closer gapped ngk plugs helped me dramatically!

[lenn]

Originally Posted by najin23

How did you clean yours?
Believe me, my closer gapped ngk plugs helped me dramatically!

I am a n54 newbie but I am mechnically inclined (I've replaced head gaskets, done timing belts and clutches on different cars). This was a 5 hour project for me. I removed the intake manifold, rotated the engine to make sure the valves were closed, filled the ports with carb cleaner and used a set of brushes (harbor freight "pipe cleaner" wire brushes), picks and a shop vac. Bolted it all back together and went on my merry way

[najin23]

I wish I had a time to do.all that. Great for u.

[Xearo]

My 135 was doing something similar months ago. Spark plug change helped a bit, but what really fixed it and smoothed it out was cleaning the intake valves/ports.

[supermac]

I ran a bottle of techron through my tank and WOW, it made a difference in cold startup misfires. 5 months later however, it is starting to come back.

I guess it is time for some more.

[Craig]

Regarding the Techron - it's been a year for me so I'll have to put some in.

Well, from reading the responses.....maybe the presence (or absence) of the cold idle exhaust misfire/hiccup is somewhat of an indication of the need for intake valve cleaning....

It would be nice to discover that this type of audible signal from the engine is informing us of sludge on the intake valves. Mine has 57k miles on it and I was trying to wait until 75k to clean 'em based on what I've read.

If anyone plans on doing an intake valve cleaning in the near future please record your cold idle before the cleaning for comparison and then post it.

[beakmoney]

My intake valves were cleaned(apparently anyway) at 39k, same misfire at cold start...nothing has really changed in the last 12k. My plugs have about 6k on them....maybe it's time to check the dishonest dealers work..

[brokenvert]

My car has done this since it was new. Its just normal N54 idle I guess

[dmak]

My n54 does the same even with intake valves cleaned, New plugs, newer injectors. It doesn't seems as bad before ******* dp was installed tho. Which makes me suspect the cold idle tune from factory was tuned with the restriction with te cats, now that I m ******* causing the tune to not run as smooth. Also remember the o2 don't work until they warm up. So on cold start car is running on base map

[minelson33]

I bought my 08 535xi with 85,000 miles with the same issue... More prevalent with colder temperature. Replaced spark plugs, coils, vanos solenoids with each upgrade offering some sort of benefit, just not correcting the cold idle.

Recently, walnut blasted the intake valves and all cold idle stumble and miss is gone. It's been a week of <60 degree mornings and nothing but smooth running.

Some pics of the process at https://goo.gl/photos/7B7am2uyjCQf6E9g8

[bdhh]

It doesnt take a lot of gunk to affect the valve train, Especially when cold.
I had 40,000 miles on my car when I bought it & it needed a walnut blast period!
Any upgrades from stock magnifies any minor issues. If you do a lot of city driving that is considered severe duty. And maintenance needs to be done sooner. You want it to run smooth, just accept the fact that these cars are high maintenance & expensive if you can not DIY.
And fuel additives will do nothing for the valve gunk because the car is direct injection, & the fuel is injected after the valves.