Hi All.

I have a very annoying issue with my car at the moment. Its a 2007 R56 MCS with 60,000 miles on the clock.

Its running quite a few mods:

Decat
Remap
Intake
FMIC
etc

Recently it has developed a nasty misfire under load in 4th 5th and 6th anywhere past 4k or 5k. To describe what it sounds like would be a machine gun going off.

We put new plugs in a few weeks back and its been fine, today it has started doing it again. The car had a decoke less than 20k ago, 6,000 mile oil changes and very well looked after. HPFP was replaced just over 2 years ago.

Anyone got any ideas what going wrong?

Possibly coil packs?

 

Machine gun sounds huh? Sounds like it could be pinging. Have you checked the level of carbon build-up?

 

I can ask them to take the inlet manifold off but I would be surprised, it had a walnut shell decoke maybe 10k ago and I don't do motorway miles or short journeys so it shouldn't be too bad.

I think we might try a stock map next, I had read quite a few people mentioning this kind of misfire over 4-5k rpm but no real clear cause or solution.

 

What map are you using? I had a similar issue to this when running an AccessPort. Kind of "pop-pop-pop" at WOT with a little bit of black smoke out the tailpipe.

 

I am running a DNA Tuning map.

The car runs perfectly and boosts fine in 1st, 2nd, 3rd. No cold start issues, no lumpy idle, no puffs of smoke, just when you hit 4 or 5k in 4th or above it just goes mental, probably 3 bangs per second and its constant. I have a decat and challenge exhaust so it really does sound like a machine gun.

 

Yea I would think DNA would be OK. That's what I have now with no issues. The way your describing it still sounds like a ping to me, but possibly I am wrong on that. I guess trying a stock map would be the next best test.

 

Short trips when the motor is cool can be the WORST for carbon buildup....you said 20,000 km...then 10,000 km....know how long ago?
If you were MUCH higher on the miles, I would suspect the coils.....
With the motor running....do you have lots of blow by? No issue with the dipstick getting blown out right? I just say this cause a few folks running aggressive remaps HAVE cracked the skirts around the wristpins on the pistions....but massive blow by is the tell here in most cases....
I am more a of a gen1 guy...so good luck!

 

Sorry for the miscommunication, off the top of my head the decoke was done at 50,000 miles on the clock so that was 10,000 miles ago. The car is just a weekend fun car and does track days. I never do short journeys in it, just hard road miles through driving trips of 100 miles of track miles every few months.

 

The map isn't too aggressive, it peaks at 17-18 psi and its a flat boost curve, I have a stack boost gauge and when its misfiring the boost is still stable at 17-18 psi.

 

George, you absolutely need to get the codes read. Properly read, by a BMW dealer, an autologic or bavarian technic etc that can read the BMW fault codes.

This will confirm whether or not there is a misfire, and if there is anything else going on. This is crucial, the diagnosis is completely different if it is only 1 cylinder misfiring vs all 4.

If it is only 1 cylinder then you are probably looking at plug / coil pack.

If all 4 are misfiring, then that is much harder to chase down.

Having said that, the commonest cause of misfires, especially on tuned cars, is a bad batch of fuel. This can be for various reasons, old stale fuel, contaminants etc. You should run the tank down with some low load driving, then fill it up with the best 98-99RON you can find, even better throw in a few litres of E85 or good octane booster. See how it behaves then.

 

Ok cheers for the help.

 

Just spoke to my friend that worked on the car last time when it had this issue and it was just a code for a misfire on cylinder 3 only.

So possibly faulty/clogged injector, plug, coil pack, poor quality fuel.

 

Very first thing....
Move the coil.....see if the issue follows the coil.
On other cars, like Toyota's, I have had very bad luck with nonoem coils...with them lasting 3,000-10,000 miles...Chinese junk...

 

If on one cylinder only then it is most likely a plug or coil issue

 

Did you get this figured out George?

 

you know what? i just looked up this thread because i noticed a similar issue with my 2010 S with 52k. it runs great and all when driving normally, but in some places, IE, large bridges on the freeway, i dont always shift up to get higher RPM. sometimes ill just use the accelerator and use the boost to get me up an over. but i noticed when im in the boost for an extended period of time, it starts pinging and popping. the only time it does this is when im in the boost for a long time which leads me to believe that the intercooler isnt really working like it's supposed to and it's just super hot air getting in there.
am I wrong with this assumption? or do you think it's something else? Im not running any mods and I recently put in new spark plugs.

like i said though, it's only when I'm in boost for any extended period of time. like as it builds up but before overboost. Also... it's not showing any MILs.

 

i have the same issue. Running 1.4bar boost and pass 5k rpm on high load it misfire and pop loud. after months of trying to figure out, finally got a on the road diagnostic and found one of the cylinder injector having a negative -4 at fuel flow at high rate. Fuel pressure on rail however is consistent. Going to replace the injector but wonder if there is a uprated injector available.