I'm not sure if this is my first post or not, but it's definitely been awhile at the very least. If you're reading this, I hope you're doing well and managed to have a pleasant Thanksgiving.

Now let's get to the meat...

I am the proud (4th) owner of a 2011 MINI Cooper S (N18) with a manual transmission and 112k miles. It had some fine-wine kinda age to it when I bought it, but was in generally good condition, all things considered. Nevertheless, I've buttoned it up quite a bit since March - suspension, brakes, axles, front main seal, spark plugs, and all the filters (including fuel) - without any issues... until now.

I know from a fair amount of reading that our MINIs have issues with carbon build-up. The previous owner's brother was a MINI tech and a claimed to have done a cleaning before selling it to his brother before it ended up in my hands only 5k miles later. Anyway, I recently decided to replace the valve cover and figured I'd install a BSH catch can while I was at it to hopefully alleviate some of the build-up and prolong the engine life a little. Everything went smoothly and the engine ran fine after the installs. Next, I decided to run a can of CRC Turbo/Intake Cleaner through the system just to give it all a fresh start. Followed the instructions on the can, again with no issues. After the one-hour heat soak, I took the whip out for a 30-minute joyride and all was right in the world... zippy, responsive, and smoother and slightly quieter than before. That was Monday (11/23).

Tuesday morning (11/24) was cold here - mid 30's - but nothing the car hasn't seen before. Started right up like normal and I headed out. After about 2 miles, things got rough... literally... like I thought the transmission had died or something. Then the CEL popped followed immediately by the Limp Mode indicator. So I got it back to the house, noticing that it drives okay in 1st through 3rd gears, but really doesn't like 4th for some reason (maybe just because of the RPM ranges; possibly irrelevant), and I pulled the codes. I thought maybe they were a cold-weather fluke, so I cleared them, unplugged everything and cranked the car up. It started without issue, but within 20 seconds or so we were back to a rough idle and right into Limp Mode again. I popped the hood and spent some time checking my work from the previous evening and found no issues, so I pulled the codes again and got the following: (See "MINI 1 (INPA).pdf")

Next, I pulled and reinspected both the valve cover (not an OEM part, but plenty of good reviews and a 3-year warranty) and catch can kit. I removed and inspected the passenger-side PCV setup on the valve cover - no noticeable issues. I checked all the plumbing for the catch can - no noticeable issues. I checked the the MAF, intake tube, and anything else I could remember touching - no issues. So I reinstalled everything, cleared the codes, let it sit for a bit, then started it up again. Aaaaaaaannnnnd no change - started up, no problem, then right into rough idle and Limp Mode showing the following codes: (See "MINI 2 (INPA).pdf")

I spent some time searching, reading, searching, reading some more, and I've explored several possibilities...
1. High Pressure Fuel Pump - seemed to check all the boxes except that I've never had any problems with starting. My issues are otherwise immediate and constant, and the engine warming up makes no difference.
2. Timing - but why the next day, and why so suddenly while under such a mild load? Also, no "death rattle" and the commonly snapped upper guide was still intact when I pulled the valve cover. Also, also... it runs perfectly smooth at idle in Limp Mode (1k RPMs instead of the usual 750-800).
3. Coils and/or spark plugs - pulled the plugs and they all look great; swapped the coils around and found no consistent patterns.
4. PCV system - considering the aftermarket valve cover could be an issue, but it worked flawless during half an hour of spirited driving. What could've happened to it overnight?
5. Vacuum leak - checked the pump and all the lines I'd worked around. I can't see or hear anything, but I haven't done a smoke test. Also, wouldn't there be other codes associated?
6. Intake Manifold Pressure Sensor - pointed out by @yeticat99.
7. Camshaft Position Sensors - discussed in a few newly discovered articles as potentially causing problems without throwing their own malfunction codes.

I was ultimately leaning towards replacing the HPFP, even though the one that on there looks newer than the rest of the engine. Then (just yesterday, 11/26) I realized that I had the software to read sensor values so I went out and gave that a shot with BimmerLink (just because it's a little easier to use my phone) and got the following: (while at idle, after again clearing the codes and again reentering Limp Mode within 30 seconds)


BimmerLink selected sensor values while idling in Limp Mode.

So the rail pressure ran from 68bar at idle to 110bar at 4k RPM which I assume means that the HPFP isn't the issue. Everything else seemed to be doing what it's supposed to, at least as far as I know.

- The intake manifold pressure (0.9bar) never changed regardless of RPMs - I revved up to 4k which is the max in Limp Mode - but I don't know if it's supposed to.
- I did the old school oil cap check, even though I don't know what the hell it means, and there's a fair amount of negative pressure (suction under the valve cover, and the engine idle dropped when the cap was pulled, which I believe is normal (but I could be wrong).
- I pulled the fuel tank cap and nothing happened. I've read something somewhere about a normal amount of minimal suction being present at the filler opening, but I noticed none. I have no idea if that's normal or not.
- I haven't noticed any smoke from the exhaust, I don't appear to be going through an excessive amount of oil, the engine isn't overheating, and I can't smell any fuel around the car or in the cab.
- I checked all the fuses in the engine compartment just so I wouldn't be "that guy" (because I have been before) and they were all good.

In the absence of any other codes or obvious damage, I'm not even sure what else to look for. I generally love figuring things out and doing as much work as I can on my own, but at this point I'm at a loss, and I'm getting pretty desperate. Any help at all would be greatly appreciated. Thanks.


UPDATE 1 - 11/28:

So I tried disconnecting the MAP sensor (as suggested by @yeticat99) on the intake manifold which did end up throwing code (reflected in "MINI 4 (BimmerLink).pdf"), but which had no noticeable effect on engine performance - I disconnected it while the engine was running and nothing changed.

So I turned off the engine, cleared those codes and went to work...

I went ahead and took a closer look at the intake manifold and throttle body. There was an unexpected amount of oil (or a mix of oil and residual intake cleaner) - maybe an ounce - inside the area where the hot-side intake hose couples to the throttle body, as well as a fair amount coating the inside of the manifold. It's hard to say how old all that is, though, since I've never been that far into the engine before. The valves still have some carbon on them, but it's not the worst I've seen. I'll give the SeaFoam treatment a go here in the near future just to clear out the valve completely.

So after checking all the wires, vacuum hoses, gaskets, cleaning out the oil, and reinstalling everything, and having previously cleared the old codes, I popped the key into the ignition to read the sensor values with the engine off and got the following:


Car on, engine off.

Then I cranked it up, and got the following immediately after startup (running between 1k and 1.1k RPMs), before any codes had reappeared:


Car on, engine on, immediately after startup with no codes yet.

Then, after the initial burst of fuel during startup, the idle dropped to 800 or so and all the usual stuff happened (rough idle, then CEL and Limp Mode after about 15 seconds). Here's what that looked like, along with the codes that reappeared: (See "MINI 5 (BimmerLink).pdf")


Car on, engine on, after codes thrown and Limp Mode engaged.

The codes show cylinder 1 being consistently individualized as a culprit among the other "multiple" codes, and I think that coil was the cylinder 3 coil before I moved everything around, so I'm gonna mess around with that later on (thanks to @thefarside for pointing out the relationship), as well as probably replacing the MAP sensor just to see if that does anything.

And here's where we are now. The only things that aren't stock and aren't visible are the intercooler resonator delete pipe, the interior noisemaker delete pipe, and the AFE dry panel air filter. Let me know if you see anything that stands out that I should go have a look at at. Thanks again!


Not too bad for a 10 year old engine compartment.


UPDATE 2 - 12/2:

I didn't control for variables (I installed everything all at once), but I replaced the camshaft position sensors, the intake MAP sensor, and all four ignition coils, and that seems to have done the trick. I'm immensely grateful to everyone who responded with insights and suggestions. Thank to you, I'm now committed to manually cleaning out the intake valves very soon, followed by completing a throw-out bearing and wastegate rebuild on the turbo. Hopefully, I can stretch this little baby out to near 200k miles. Thanks again!

 

This is the only thing that jumps out at me as odd. I would think manifold pressure would show vacuum at idle, then build boost with load? Maybe try unplugging the MAP sensor and running your test again?

 

Thanks for the suggestion. I'm happy to try it, but what would I be looking for in terms of changes? And what might such changes indicate as the problem?

 

69 Bar = 1000 psi - seems a bit high, typically 700 psi is what I recall seeing at idle
.9 bar MAP(true?) is likely about right for a Valvetronic engine. On a Valvetronic engine, valve lift is the primary control of airflow, not the throttle plate

The coil codes are only on cylinders 1 & 3, true?
Will you get the same codes (only on 1 & 3) if you swap coils between 1 & 2 and 3 & 4, respectively?

If the codes don't move with the coil swap, then that would seem to point to fouled injectors. One could speculate that fouled injectors might explain the high fuel pressure.

I don't what the normal range for the WG load is at idle, but 70% seems way high. That likely points to a badly worn WG pivot shaft, which is what you would expect to find on a OE 122k mile turbo. That is not likely to be related to the misfire codes. Do you have enough experience to wiggle the shaft and know if the play is too much? With respect to the car, wiggle the shaft from front to rear, then left to right. For a badly worn shaft left to right will be way more than front to rear

I don't know what Mini's diagnostic fee is, given the ambiguity it might be worth considering, depending on how quickly you need to find resolution.

Suggest you do a compression test, just to rule out a catastrophic mechanical failure.

 

Nope: not a worth while test. See my post above - A Valvetronic engine will show very little change in MAP as a function of load at idle. Obviously once the turbo comes on line, a different story......

 

Edit: Thanks, farside.

 

From everything I've read, positive pressure under the valve cover isn't a good thing --- bad PCV or serious compression leak. If you still have the original valve cover, you might try putting it back on --- without the OCC.

I know nothing about your CRC cleaner but from what I know about turbo's, it was probably a waste of time and money. If it was a fluid additive to your gas tank, you've put your entire fuel system at risk. If it was a spray inside the turbo or its immediate hoses, some may have migrated into the valve cover PCV system. (Obviously, I have a personal issue with "additives".)

 

Gave this a shot and it threw a code specific to the MAP sensor, but nothing about how the engine was running at the time changed. I honestly don't know what that means, but it is interesting. I've updated the OP to reflect such. Thanks again for the suggestion.

 

I think 70bar (1000psi) is normal for Limp Mode since it bumps up the RPMs a little to account for the misfires.

Thanks for pointing out the connection between cylinders 1 and 3. I think cylinder 3 was identified during the initial problems and it switched to cylinder 1 after I moved the coils around, so that's a thing worth exploring.

As far as the wastegate, I noticed today that it was open at 10% when the engine wasn't running. I guess that mean that its not closing completely which probably isn't a great sign. I'll be addressing that as soon as I've determine that the engine doesn't need to be replaced. I haven't thoroughly assessed play in the actuator shaft, but I will tomorrow.

Thanks for all the insights and suggestions!

 

I've read the same thing, actually. I meant to say negative pressure, as in just a little bit of suction, which I think is normal . I've updated the OP to reflect such, and thanks for pointing out the error, and for the suggestion.

The CRC cleaner goes into to turbo inlet after the MAF sensor. I may have blown a bit of carbon off the valves, but after poking my head down and actually looking at them today while the intake manifold was off, it didn't do quite as well as I'd hoped. I think most of the work it might've done would've been within the turbo itself, cleaning out old oil residue from the pre-catch-can PCV setup, which may help to explain some of the residual oil in the throttle body and intake manifold. The valves aren't bad, but they also aren't great, so I'll have a little more to do once I figure the rest of this out.

I don't have much experience with additives other than Z-Max. I've used the oil/fuel treatments every oil change for 5 different cars over the last 11 years. I honestly don't know if it really does anything, but I don't know for sure that it doesn't either and all the other cars have held together really well even into the higher mileage ranges.