Stock 2007 MCS R56 with 66K miles

Issue
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If I drive around in stop and go conditions (around town or rush hour) the engine starts to knock for a moment when accelerating from a stop (1st gear). This only seems to happen after it has warmed up and is on an incline, even modest ones, and the temperatures are mid-70F+. Now it's starting to happen in 3rd gear as well, though it's much milder. I have no CELs.

Vehicle Care/Background
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I fill up with Chevron or Shell 91 octane. I've had the carbon cleaning performed a couple of times on the intake, so the backs of the valves are nice and clean. Oil level is spot on and clean. Had the timing chain issue addressed and the HPFP replaced by the factory about 20K ago (out of warranty, too!).

I just added half a bottle of octane boost and will monitor over the next week.

Wild Guesses, Speculation and General Blustering
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Kinda wondering if I need to do a walnut shell blasting for the cylinder heads since I've only ever cleaned the intake for carbon.

BTW: I keep seeing knocking, pinging and pre-detonation being used interchangeably. This sounds more like a loud, but short, diesel sound or "knocking" in my opinion.

Glad to hear any feedback or hear if anyone else has experienced this.

 

What did you do for the carbon cleaning? I had same issues as u, knocks n misfires. They occurred in higher stress situations, hard acceleration n driving uphill, less noticeable when just idling or normal driving. I eventually got the CEL after a while.

Had walnut blast on mine at just over 70k mi a couple weeks ago, it's running much better and smoother now. I also did "carbon cleaning" a few weeks prior to the walnut blast. The carbon clean was just a solvent run thru the intake by an independent mini shop, it didn't help much in my situation since I've not done it before.

 

The first cleaning at 40K was chemical (MINI dealership). The second cleaning at 65K was chemical and scrubbing (independent Euro mechanic). Both were intake only.

1) How much was your walnut shell blasting service?
2) Do you know if they just did the intake, or did they also do the cylinder head?
3) You say "it's running much better and smoother now," but did it completely eliminate the knocking?

Thank you for your reply!

 

1 Estimate 1600, final 1200+
2 Removed manifold, replaced gasket and did the walnut thing, not cylinder head
3 I don't drive as often as I use to, but the few times driven immediately afterwards there were still a few rough idles, but it has all passed now. It may have been like so while getting rid of any carbon that wasn't completely cleaned out, or maybe because they reset the ECU. ECU was reset to forget the learning of running with carbon build up

 

I have had the same problem (2007 MCS R56), it started happening at 45k and got progressively worse and louder after the walnut blasting. More air more gas louder knock. The problem is with most they only have the valves walnut blasted ($350-$600) and stop there, the problem is the pistons and valves in the combustion chambers look just like the intake valves, oil coked on.

So here you have valves covered in oily carbon deposits, a walnut blasting will clean the intake runners and valves. I found that using 5 bottles of BG 44K turned my combustion chambers from black to silver and now the knocking is gone! The only other way to remove the carbon in the combustion chambers is removal of the head, that's going to cost a fortune. If you're removing the head you might as well have the head ported.

 

More details to add:

Added 2/3 of a bottle of octane boost to a full tank and the knocking stopped. Outside temperatures were in the mid-70s.

Added 1/3 of a bottle of octane boost to a (new) full tank and knocking returned. Outside temperatures were in the mid-90s. Knocking was louder than in the past and continued for longer.

Knocking disappears when in Sport mode, even in 90° temperatures and under hard acceleration up hills. In fact, it sounds great.

Wondering if the ECU needs to be reset (it was replaced only 6K ago). Does this sound like it's running lean? Doesn't Sport Mode dump more fuel into the cylinders?

I took it into the mechanic today. Hoping for some answers and solutions.

 

Is your car modded?

 

Stock, no mods. I have a long wish list sitting over on the ECS Tuning site, but most of the good stuff is illegal in Cali.

 

Mine does the same thing but only when tuned. A knock in the 1500-3500 rpm range, but it doesn't happen with a stock tune. I ran it on the dyno and it was much too lean from 1500-3500 RPM, right where the knock happens. I'm having my tune adjusted and hopefully it helps.

 

Yep. I get the knocks at low RPMs. Sport Mode magnifies accelerator pedal input, dumping more fuel quicker - getting rid of the knocking for me. A lean fuel mixture sounds like a possible culprit. Is that something that can be tweaked without a custom tune. In other words, I'm wondering if that's something a stealership can actually adjust.

two250: where do you get your '08 tuned?

 

Battle tuning, they are in SoCal. I do it all through email though, dynoed mine on my roommate's dyno. It might be worth trying to find someone with a wide band AFR sensor to verify that it's lean..

 

Mine only started knocking when temperatures were 84-100 degree fahrenheit, but today absolutely no knocking today at 75 degrees. Air today was higher in humidity and moisture probably cooling cylinders better, my thinking is the 85-100 degree days is leaning out the mixture too much. A weak AFR mixture doesn't start to knock until temps in combustion rises cause the fuel (or lean mixture) to pre-ignite. Octane booster can cause your knocking to be worse in warmer weather!

Meth is the only solution short of removing the head and getting rid of the carbon on pistons!

 

Got the call from my mechanic. The cylinders are clean, so are the valves (I knew that though). The spark plugs (factory) had too wide a gap from corrosion (?) so those are getting replaced. He says that will solve the issue. He mentioned something about direct injection Audis of the same vintage are coming in with the same knocking problem and it's been the spark plugs each time. (I wonder if Audi and MINI are using the same brand?)

It's ready for pick up and has a full tank of untreated Shell gas, so I'll test it out and report back.

[fingers_crossed]

Systemlord: do you have a meth injection kit? Looks like you're in SoCal too, wondering how that works during smog inspections.

 

Good info, might as well check my plugs too, I'm at 55k...

 

No meth injection here, you don't think a meth injection would void my now 5-year extended warranty? Are there a bunch of wires connected to a wire harness somewhere in the car? I don't want the dealer or whoever performs warranty work to find a bunch of wires webbing out of a harness.

Do you think if I get an intake service performed by a BG service center that it will help remove the carbon that the BG 44K fuel system cleaner is not getting around the outside of the piston? It's a service that injects a fog like mist in the throttle body (very similar to meth) of pure cleaning solution and runs it with the engine running.

 

check your plugs and see if any are oil fouled

 

Video of mine I put in the other knock thread. Similar to yours CmdZ?

 

I replaced my plugs with new ones 3000 miles ago.

@CmdZ

You think changing my plug gap could delay the pri-ignition a bit? It pre-ignites just a hair too soon, backing off the pedal makes the pre-ignition lessen a bit. If I could somehow delay ignition I might be able to prevent pre-ignition correct?

 

OK so an update to my car. Flashed my new Battle Stage 3, and so far the knock is gone! It is about 15 degrees cooler today from that dyno video, once it heats back up I'll try to get the knock to happen. I'm still checking my spark plugs tonight...

 

Update: Fresh spark plugs installed. My old spark plugs were nice and clean, but the gap was too wide and the ground electrodes on a couple of them were no longer symmetrical due to wear. My mechanic said that the intake was nice and clean, too. So far, it's running beautifully and the slight lag between pressing the accelerator and actually moving is gone. The weather is cool right now (figures), so I won't be certain the issue is completely gone until it warms up again. I tried a couple of low RPM starts, which were a great way to demonstrate the issue, but the engine handled it like a champ. That's a really good sign.

I'll report back after I get to try some stop and go driving or when it heats up.

two250: Holy crap. That looked and sounded brutal, but I can't tell what the noises are with such a short video.

 

Yea standing at the back isn't the best way to hear the knock. Plus that was the only time it knocked on the dyno. After that the car backed the boost down from 16 to around 13.5. Not sure if it changed boost by pulling timing after detecting the knock, or if it can directly control boost via a wastegate like my truck...

Update Pulled my plugs, happy to report that they look perfect. They need to be replaced, but the plug looks exactly like NGK's picture of a normal plug at it's end of life...

 

No pre-ignition today, seriously cool moisturous air. It was 64 degrees before sundown!

 

It's been a long time coming, but the pinging source has finally been identified. I recently got a CEL and took it in for a diagnosis. It's bad. Really bad.

The culprit was insane carbon deposits everywhere. I'm the second owner. I have had 3 carbon cleanings over the 40K miles that I have put on the car. I only use Castrol full synthetic or Royal Purple and Chevron/Mobil/Shell fuel. My mechanic is convinced that the problems in the combustion chamber were caused by the original owner and that I'm dealing with the consequences.

The back of the valves looked like they had never been cleaned. The cylinder head is caked in carbon, the valve seats are a lost cause, the lifters were nearly at their limits and the valves themselves were thinning on cylinders 2 and 3.

The only good news is that the cylinder walls are beautiful and still show the honing marks.

I need to have the head rebuilt. MINI has redesigned the valves and valve guides to partially address the carbon build up issue (and they probably have a bridge they'd like to sell me). The pistons have to come out and get cleaned and polished. The fuel injectors are caked and will get a cleaning. The timing guide that MINI replaced under extended warranty is already showing wear. Mr. Tabasco will also be getting his 3rd thermostat housing.

All in... $3600.

This is a car with 77K. Caveat emptor, eh?

 

Everything has been put back together. The turbo diverter valve also had to be replaced (real cheap plastic collar). I was able to get a picture of the rebuilt head, but missed the chance to get one of the polished piston heads.

The knocking and pinging is gone now. I tried everything I could think of over the hot weekend, and the engine is just as tight and happy as can be.

I still keep expecting that obnoxious noise when I launch out of 1st gear, but it's just power now. This car is fun to drive again.

 

Dear god that's awful! And 77k miles? I have 133k on mine! I guess I'll be pulling the plugs to see what lurks on the pistons and underside of the head when I do my walnut blasting this weekend!