[cstavaru]

Hi,

This happened to me last week the first time, and it happened again today. When accelerating from a low RPM (1500RPM) in 6th gear, I felt something like a "negative power bump" like the car lost all the power for just a fraction of a second. I can describe it like a "power stream interruption" for a fraction of a second. After that single event, the car ran perfectly and I couldn't reproduce the problem again on that trip.

I wonder if this is what a misfire looks like ? I never had a misfire and don't know how it feels like...sorry I don't have a BT cable to check for codes.

I'm kind of nervous...my warranty expires in one month...

[marconi118]

I have the same sporadicaly in the exact same conditions, and yes I think it is a light misfire.

unfortunately for me there is no code, so the dealer won't do anything.

the cause: bad injector or bad spark plug coil

[TurboSid]

i get the same thing happening. changed hpfp, low pressure fuel sensor, spark plugs... nothing fixed it.

Do you have a tune?

[cstavaru]

Originally Posted by TurboSid

i get the same thing happening. changed hpfp, low pressure fuel sensor, spark plugs... nothing fixed it.

Do you have a tune?

I am somewhat stock (BMW Power Kit installed). I really hope I have some codes...I will go for a dealer check on Monday. If I were to guess between a coil and an injector, I would say injector, because it is happening when pressing the gas pedal deeply and high torque is needed...I suppose the injectors are at full duty cycle at that time. If it was a coil it would happen randomly, not in these specific conditions.

[Jed]

Originally Posted by TurboSid

i get the same thing happening. changed hpfp, low pressure fuel sensor, spark plugs... nothing fixed it.

Do you have a tune?

I had the exact same issue with mine (all stock). ~1.5K rpms in 6th gear and it stuttered. Brought it to the dealer, they checked the LPFP, spark plugs and injectors. In the end, it was severe carbon buildup-the valves at cylinder 2 were sticking. After a thorough cleaning, zero issues.

Car feels like brand new and stronger.

In your case, you may want to have your dealer take a look into that if you've done everything else.

[zsapphire7]

how did you convince them to check the valves? I would like them to clean them for me... but can i really just go in and request it for really rough idle and no codes?

Originally Posted by Jed

I had the exact same issue with mine (all stock). ~1.5K rpms in 6th gear and it stuttered. Brought it to the dealer, they checked the LPFP, spark plugs and injectors. In the end, it was severe carbon buildup-the valves at cylinder 2 were sticking. After a thorough cleaning, zero issues.

Car feels like brand new and stronger.

In your case, you may want to have your dealer take a look into that if you've done everything else.

[Alan l.]

If its indeed carbon build up related i'm wondering if some Seafoam would help you.

Worth a shot.

Alan

[zsapphire7]

Originally Posted by Alan l.

If its indeed carbon build up related i'm wondering if some Seafoam would help you.

Worth a shot.

Alan

you know, ive seen alot of threads on seafoam but i have yet to see a single one with pictures of before and after valves. Heck I want to at least see a reason why seafoam could even remove carbon buildup from the valves...

i feel kinda skeptical as to why it would help remove carbon buildup since theres no proof yet... Someone should submit this to myth busters..

[cstavaru]

I will not let them open my engine...I have bad experience with dealerships as far as their skills.My stuttering is different: only one single "stutter" happens, like a "thump", then the car goes perfectly normal.

[marconi118]

then replace the injectors, insist to have it on warranty.

[Alan l.]

Originally Posted by zsapphire7

you know, ive seen alot of threads on seafoam but i have yet to see a single one with pictures of before and after valves. Heck I want to at least see a reason why seafoam could even remove carbon buildup from the valves...

i feel kinda skeptical as to why it would help remove carbon buildup since theres no proof yet... Someone should submit this to myth busters..

I totally agree with you but i think being able to do a test like this will be very costly and time consuming. Figure it doesn't seem to harm anything its worth a shot in this case or on cars with higher mileage.

Alan

[cn555ic]

I think the early injection of meth in a relatively new engine will
Prevent carbon buildup. Just like tarter on teeth. Once it forms i don't think any solution will remove it unless you physically use vibration to jar it loose. To prevent carbon buildup you need to find a way to not even let it happen and that's almost impossible but with methanol injection i think it's a good solution. I think seafoam is useless based upon my tartar on teeth example

[michaelthepsycho]

Why are you people lugging in 6th at such low revs? No wonder there's carbon build-up... Sacrafice a little fuel for the health of your engines.

[cstavaru]

Originally Posted by michaelthepsycho

Why are you people lugging in 6th at such low revs? No wonder there's carbon build-up... Sacrafice a little fuel for the health of your engines.

Well, it happens sometimes, and besides, the Efficient Dynamics gear selector indicator tells me to change gears at 1800RPM (I have a manual gearbox). I suppose that the automatics also change gears at around 2000RPM so it's the same...or should everybody drive in DS mode ?

[Jed]

Originally Posted by zsapphire7

how did you convince them to check the valves? I would like them to clean them for me... but can i really just go in and request it for really rough idle and no codes?

I didn't have to convince them, they went through the whole decision tree for diagnosis and it arrived to carbon buildup. Luckily, I have a great dealer to work with!

Originally Posted by Alan l.

If its indeed carbon build up related i'm wondering if some Seafoam would help you.

Worth a shot.

Alan

Depends on how bad the build up is-they did an initial cleanup (pulled off the intake manifold, scrubbed the valves), but it was so bad, they had to pull the head and have it thoroughly cleaned. My car has 75K miles, btw.

[zsapphire7]

I think ill see if i can get the dealer to clean it sometime.. i guess ill try to sea foam and meth injection and hope for the best otherwise...

[ETS Michael]

The dealer is doing this to my car as well. Should be done tomorrow with the carbon clean up. I drive 40 miles a day at 2000rpm in sixth. I think this could be the reason for build up, but who knows. My hesitation is more around 2500rpm.

I'm also wondering if the ECU is trying to learn my driving habits and leaning it out on my cruise speed.

Who knows.. The car spends more time at the dealer then me driving it.

Michael

[reggiecmah]

This is happening to me today on the way home.. ughhhhhh

[TMR]

take it to the dealer and have them go for a ride with you with the service manager. As long as you can reproce it... make them fix it.

[MDORPHN]

Originally Posted by cn555ic

I think the early injection of meth in a relatively new engine will
Prevent carbon buildup. Just like tarter on teeth. Once it forms i don't think any solution will remove it unless you physically use vibration to jar it loose. To prevent carbon buildup you need to find a way to not even let it happen and that's almost impossible but with methanol injection i think it's a good solution. I think seafoam is useless based upon my tartar on teeth example

I'd run a good oil catch can.

Neil

[Alessandro]

same happend to me they exchanged HPFP and injectors cur runs like new again.

good luck

[Al Blue4.6l]

Originally Posted by zsapphire7

you know, ive seen alot of threads on seafoam but i have yet to see a single one with pictures of before and after valves. Heck I want to at least see a reason why seafoam could even remove carbon buildup from the valves...

i feel kinda skeptical as to why it would help remove carbon buildup since theres no proof yet... Someone should submit this to myth busters..

google brings up a bunch of results. here is one:

http://forums.audiworld.com/showthread.php?t=267776