Carbonization in intake valves

[jparnes1]

So, I've been reading about how direct injection engines can lead to carbon build up in the intake valves and in fact, BMW recommends preventive maintenance on our engines every 30 - 60 K miles (not covered under warranty unless there's a problem related to this). I have also heard that periodically adding a fuel system cleaner like Techron to the gas tank can alleviate this build up.
My question is this: if the gas is sprayed directly into the cylinders, bypassing the intake valves, how does Techron manage to get to the valves to clean them?

[fl_cyclist]

I know this was a big issue for Audi's. They would get engine failure messages and low power then need a complete engine pull/breakdown and cleaning. We had a Q5 and I was reading on this most think that as you say additives will not help as the issue is carbon buildup due to lack of fuel passing over the valves due to direct injection, no fuel no fuel additive. I think it also has to do how the engine is designed I have not heard of this as being an issue with BMWs and with the Audi's the issue was much less with the Turbos, the assumption was they ran hotter which helped?

You can read a lot about this topic on Audi forums

[jannisa]

Well it doesn't. It will just help injectors a bit, another weak point on the platform. No wonder the n54 operates at such high oil temperatures to burn off some of the oily blowby.

[nicknaz]

jparnes, have you been experiencing any symptoms or is this just more of hypothetical question?

It seems like the build up on valves shows similar symptoms as injector issues, and I wonder about whether this is some misdiagnosis, since injectors have been a sore spot on N54 since introduction

[jparnes1]

Originally Posted by nicknaz

jparnes, have you been experiencing any symptoms or is this just more of hypothetical question?

It seems like the build up on valves shows similar symptoms as injector issues, and I wonder about whether this is some misdiagnosis, since injectors have been a sore spot on N54 since introduction

No symptoms Nick, just been reading that this is a problem with direct injection and wanting to try a preventive approach.

[nicknaz]

Originally Posted by jparnes1

No symptoms Nick, just been reading that this is a problem with direct injection and wanting to try a preventive approach.

http://www.e90post.com/forums/showpo...18&postcount=1

Some advice in that thread. I definitely agree with step #1

I found these tips from another BMW forum on preventing carbon build-up on the back of the valves. Providing it as information, hoping it can help anyone who shares this concern. I don't think I am allowed to provided the link but I copied and pasted the post for from the member who posted it on that forum.

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To all of you. Take this from a guy who had an N54 with 70k plus miles on it. I dealt with all of the symptoms you guys described and think I have reasonably figured out how to work around it. First, you MUST drive the car at sustained high RPM's at least once or twice a month. I had all of the symptoms you guys have described in this thread and they started around 30k miles. By 50k miles the engine ran better than at 30k miles and I am about to explain how I accomplished that without the shop ever looking at the motor.

1) At least once a month and preferably twice a month take the car onto an interstate or high speed road. Warm up the motor at low RPM's and then put car in 3rd gear and do 65-70 mph. It will turn about 4500 rpms. Drive like this for a good 20-30 minutes. You will notice that the engine pulls harder and runs better. This method helps to burn off that oil and carbon on the back of the valves, but this only works if you do it often and before the buildup becomes an issue.

2) Use BMW fuel system cleaner plus every 5k miles. It does not wash over the valves, but the injectors on this car do seem to foul easily. In addition, stick to BP/Top Tier gas. I have tried every brand of gas and I have the best luck, in the N54, with Shell, Chevron and BP (in that order).

3) Use different brands of gas every other tankful. If you like to use one brand repeatedly then after 5 tanks of that brand switch to another brand for 2 tanks. This helps to get rid of gas additive buildup on the injectors...it does happen and some of these stumbling and hesitation problems are not carbon buildup but rather injector buildup.

4) The obvious. Change the oil every 7500 miles or less. It does help.

Trust me guys. I learned this stuff from a master BMW tech/foreman who has been working on these cars his whole life. While direct injection is newer technology, he knew enough about it to counteract the carbon buildup problem. He drives an N54 and has 145k miles without ever doing a carbon cleaning. He does exactly what I do and I know other people with high mileage N54's that run great following this routine. I sold my N54 with over 70k miles and the used car manager said it was one of the best, if not the best, running N54's he has driven that was out of warranty. I told him what I am telling you and explained how this ritual does work. I plan to do the same to my N55. Lastly, those of you that drive slow city driving...this engine will hate you and punish you. Make sure you do what I suggested even more so than the highway commuters. The engine needs to get hot to burn off that oil blowby.
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[jannisa]

Makes sense.

[cuddapah]

From http://bmwtechtips.blogspot.com/2013...m-cleaner.html

"While it is true that this additive is not as effective in a turbo charged vehicle with direct injection since it doesn't help clean the intake valves, it still removes deposits from the fuel injectors that restrict normal performance."