Good morning NAM,

Please forgive me if this topic has been discussed. I always use the search feature for my questions. However my results kept bringing me to ‘Super Knock’ related topics and I am not sure if that is my case. Please read on.

After some concerns I had with some smoke from the exhaust, I just replaced my spark plugs (about 1500 miles ago and gap increased about a thousandths) and car was running stout. Just this past weekend I experienced some heavy hesitation during WOT (in all gears 2 and higher). The engine seems to cut out and the exhaust pops a little, as if there wasn't enough fuel. If I accelerate gradually (almost full boost) there are no problems. Only when I apply WOT say from 3k RPM’s. No CEL’s oddly enough. I will scan it tonight for soft codes with my AP.

Now the problem doesn't always rear its head. Yesterday I ran out to do some errands and had no problems. However Saturday evening there were all sorts of hesitation issues. Out of the 4 or 5 times I got on it I had hesitation issues. The issue is present no matter what time of day (temperature). I have not done performed the carbon clean out yet (was hoping until Spring) but wanted your thoughts on this matter.

Otherwise the car drives as normal. Idles find, starts fine, moderate acceleration is fine. No other issues associated. It started last week and I am about ½ way through a full tank of gas so I ruled out possible bad gas. Although I am not totally ruling this out. Your thought?

 

Carbon Buildup, failing HPFP, or vacuum leak (usually associated with a code though)

 

Thank you ThumperMCS. Guess I'll start with the carbon removal.

 

It's predetonation. And if you live in CO or any other place that only sells 91 octane it's probably bound to happen. Carbon build up can be one of the causes with the predetonation. Clean it out as you're going to do. I know you replaced the spark plugs but Way Motors sells cold heat spark plugs which I would recommend. BMW recommends 93 octane as a minimum fuel grade, which stinks for all of us who can only run 91. The lower grade gas burns quicker. Quicker burns mean higher engine/ cylinder temps. Higher temps produce hot spots, hence predetonation. I replaced my engine last year at the end of Oct and I am just now at 15,000miles. I had the exact same issues you are having at 8,000 miles on a brand new engine. I took it into the dealership, they said it was bad gas (this was in April 2013). Tried all sorts of fuel system cleaner and they replaced the HPFP (warranty) and I still had the problem. I had ever so slight of build up which has been cleaned out. It helped but the problem came back, but less often than usual. My issues came from WOT pulls in 3rd or above at low rpms. It would sputter and back fire like you're describing. When my car sputtered it would push black 'dust'. My mechanic buddy suggested E85 (about 1-2 gal with 91 octane). I thought he was crazy. Then I saw Terry at BMS suggest running 20-30% E85 to achieve a 93 octane rating. I gave it a go and haven't had predetonation issues since. I also threw in those cold heat spark plugs three weeks after just to be safe. I have no issues at any RPM at any throttle opening.

BTW if I mispoke on a technical issue, I apologize. I do know my issues were predetonation though and my symptoms were exactly like yours. I typically do 1 gal of E85 per 5 gal of 91. Get rid of the carbon first since my assumption is that you have more that 30,000miles on the engine and I have heard people have enough carbon build up at 20,000 miles to cause a predetonation.

If that doesn't work I wouldn't have any direction for you and I would assume going to the dealership or a Mini shop would have to inspect it.

 

Given the ease of the carbon removal, I will pursue that avenue first. I know I'm overdue for that.

Then we'll cross other bridges should this not remedy my problem.

No worries on tech speek. I understand it all :-D

 

Ease of carbon removal? I am new to these cars, so am curious about this. I'm familiar with the problem and causes, but sounds expensive. I am past the point/age of doing the more involved work on my vehicles myself and this doesn't sound like an inexpensive procedure to me. What is the going price to have this procedure done these days?

 

Hi vetsvette, I will be doing the decarbonisation of my intake ports and valve stems next week. In the war of money versus time I have more time so I'll do the work myself.

I have heard of this being done at the dealer for around $600+ for the walnut blast. My buddy (European mechanic) says it's not worth it because it doesn't clean the back of the valve stem well enough but beats not doing it all.

I have heard of people who have done this and the performance gain/throttle response/milage is worth it.

 

There is multiple thread about the Media or Walnut blasting.

They are using two main tools from MINI:

Extraction Adapter - MINI


http://www.ecstuning.com/Search/SiteSearch/81292208038/ES2166079/



&

Strahlsonde MINI ( beam probe)


http://www.ecstuning.com/Search/SiteSearch/81292208032/ES2166078/



Then creating there own vacuum and media blaster system with those tools.

Here a good thread which contains a DIY.

https://www.northamericanmotoring.co...-cleaning.html

&

Shorter write up.

https://www.northamericanmotoring.co...ves-today.html

Thanks and good luck.

 

Good morning,

I spent the better part of last Saturday (11am to 6pm) removing carbon from my intake valves. This was actually a very easy procedure, just very time consuming, very. I did this by myself so in order to get the valves to close I put the car up on a jack, removed the passenger side wheel and removed two of the front inner-fender fasteners and turned the crank (clockwise) with a socket/ratchet until I felt the compression stroke (most resistance during the turning process) and this was how I knew the valves were closed. I also sprayed a little of the carb/choke/throttle body cleaner in the ports to determine which valves were closed. While I worked on one port (outer cylinders are synced as are the inner cylinders) I sprayed the cleaner into the other port to allow time to soak.

This was a very nasty set of valves (see pics). Carbon was caked on the valve stem and the top of the valve. I am not sure how the hell this thing ran before. I had to clean them 5+ times each port. I invested in a long pick set (6 pieces) to which I used very one (very helpful). I also used a dogs tooth brush (from Petsmart). They are long and they have a small head with stiff bristles on them to get between the valve stem and the outermost part of the port. Worked like a charm. I also had an array of metal and nylon brushes to clean ports.

Interestingly enough my throttle body and runners once removed from the car were not even close to oily or coated too badly in carbon/oil. Not sure how the intake ports could be so bad(?). Nonetheless I sprayed them clean with the B-12 Chemtool (Carb choke throttle body cleaner) .

I found some instructions here on NAM that were very helpful. The one thing the instructions did not tell me/you is that there is a bolt on the lowest part of the intake manifold/plenum that supports the bottom of the manifold/plenum. This bolt was only accessible from the top (my hands were too large to attack it from the bottom). This was my only ‘hold up’ as I tried to figure out how the hell it was still being held onto the motor. Another thing that would have saved my some time was remove the manifold/plenum with the intake tube (the 90 degree elbow that connects the intercooler plumbing to the throttle body) by disconnecting the ‘quick disconnect’ to the left of the motor just before the piping turns down towards the sound generator.

Other than that the job was a snap. My other problem is that this did not fix my hiccup that the car has while lugging the motor from say 2-3k rpms. I believe this is a fuel pump issue.

I received a letter in the mail about my timing chain so I’ll have the techs check it out then.

If you have any questions for me let me know. I have replaced my water pump, thermostat housing, turbo oil supply lines, lowering springs and have now cleaned my intake valves. While the lowering springs are the easiest thing I've done the intake valves are pretty easy too. Knock on wood….