I’m the owner of an 06 MCS, with around 189k miles. Mods limited to a DDMWorks intake and racing headers + test pipe. My car’s been suffering from occasional misfires and limp mode driving for the past year. Since these symptoms have come up I’ve replaced the coil pack, the ignition wires, spark plugs. Really doubt it’s a spark issue.
Next I replaced the throttle body, admittedly with a used but original unit. Replaced the cat with a test pipe which solved the misfires for a while as I had a clogged cat.
Up until a couple weeks ago the misfires and limp mode have gone away, but it seems the issue has returned.
At first I suffered from the once-in-every-several drives hesitation from the throttle, and then limp mode. The issue became more frequent to the point where I’d have to stop and turn off the car, and turn it back on to get rid of the limp mode several times a drive, and with a 70% success rate as sometimes I’d have to crank the car multiple times due to a misfire.
I had a buddy come over with a WiFi OBD scanner to read the SES codes. Didn’t think about screenshotting the results but after clearing the initial codes and going for a drive the car came up with a throttle related code after another limp mode/misfire combo.

As of now, the car won’t start on first crank. It needs two or three cranks to start and it’ll idle rough. Rare misfires, but the throttle is barely responsive. WOT yields slow revving and laggy response. Driving the car results in bogging down after giving it any more than like 35% pedal input.
I sprayed compressed air into the connections for the throttle body and the pedal itself. BPV seems to want good pressure to open, I hear an audible click as I close it, and to make sure I did the zip-tie trick to keep it closed under acceleration and the car STILL hesitates to accelerate. A drive now results less in misfires and limp mode and more flat out slow acceleration, where 30 mph is barely attainable for the car unless you give it quarter throttle.

I have another *new* used throttle body on the way, since I opted for a warranty on the one in the car. Out-ruled the possibility of a fuel issue since you can hear the pump going when you key in the ignition and although a filter replacement is probably needed, I doubt it’d cause this level of problems.
Intercooler boots look okay, they’re seated on firmly and I feel no air slipping through them.

I’m out of ideas, and I don’t have the money to throw parts at the car as much as I’d love to. Could the MAP sensors be at fault? Harness connections to the pedal / throttle body? I hope the specificity of my symptoms is enough to garner a proper diagnosis from someone.

 

Just for the sake of it, try re-syncing the drive-by-wire throttle.
Ignition on, engine not running - floor the gas pedal & hold it for a good 30 seconds - ign off & key out.

 

Tried this out yesterday, and it seems to have solved the prolonged cranking and initial rough idle. Took the car out for a spin in hopes it was solved and the hesitation persists. It’s as if the car doesn’t want to apply 100% throttle when the pedal is to the floor.

 

I think I'd give it a day or two to see if there's a brain somewhere that needs to re-learn your driving habits.
You might try some carb cleaner in the throttle body - I don't think compressed air will do much.
What color are all four spark plugs after a decent run?
Is it possible the timing chain has jumped a tooth?

 

I haven’t been using the car since Friday due to these issues, it won’t be learning any driving habits until it’s fixed
Carb cleaner in the tb sounds like a good idea, though my new one should come in tomorrow so I can try it out. I sprayed compressed air into the connections, not the body itself.
I checked the plugs Friday and sprayed them with brake cleaner. They were mocha colored but to my knowledge not fouled. Gaps were fine and even on each.
Oh boy, I haven’t considered the possibility of a timing issue. Could the guides have failed and caused these problems?

 

Took the car for a spin and noticed a couple in an Electric Blue R53 parked at a local convenience store and stopped by to ask them what could be causing my throttle issues.
*It should be noted that I started the car today (took two cranks) and noticed no engine lights and fine idling. All seemed well until I went for a drive, wherein the car seemed to again only respond with limited acceleration when met with WOT.*
In any case, the guy told me it was most likely the pedal to be the culprit. The module attached to the pedal assembly probably has gone bad. Seemed like he knew from personal experience. I’ll have to order one late this week and see what it does.

 

Have you actually checked your fuel pressure? Most fuel pumps will either work or not work but I did have one on a 2001 F150 do the exact same thing you are describing. It was hard/slow to start and misfired like crazy under WOT but once running would do OK as long as throttle input was minimal. I hooked a gauge to the fuel rail and took it for a drive, it wouldn't maintain sufficient fuel pressure once the demand went up.
Yes I realize they are two VERY different vehicles but it may be worth looking into.

All that being said, testing the DBW throttle is not bad advise. Timing jump is also possible but I would think that should throw a code.
Posting up what codes come up may better help in the diagnosis.

 

It’s funny you say this because you’re exactly right.

I ended up buying an accel pedal and installed it yesterday, to no avail. Went for a drive, again thinking the car was running fine until it would start to idle rough after half an hour, and even turn off.
At this point I was at a loss.
Scheduled an appointment with a local, reputable euro shop and drove home just barely making it. The car ended up sitting on my street for some hours until my dad came home because it wouldn’t even crank after it died while I let it idle for a bit in the time it took for me to open the garage.
After failing to pop start it, I guess the jerking of the car caused sediments to move and the car was able to start. Now I was suspecting fuel, and my suspicions were confirmed after removing the rear seats and turning on the ignition, in which you could hear the pump struggling to churn gas. I decided to order a fuel filter off Amazon and removed the old one, which came out charcoal-black, and the gas in the canister was also muddy.
Now I’m hoping my pump hasn’t gone bad yet, and my injectors haven’t suffered from the sludge. My filter arrives tomorrow, I will post an update then.

 

I've had cars with driveability issues from extremely dirty fuel filters but never to the point it wouldn't run. Not saying they cant, just not in my personal experience. Here's to hoping your pump is still OK! I don't know how easy it is to test fuel pressure on an R53 as I have an R50 and haven't looked into it but for what its worth, if you still have issues after the new filter, Harbor Freight has an inexpensive fuel pressure test kit that works well.
I would caution against aggressive driving with fuel delivery issues because its very easy to destroy a motor with a lean condition (ask me how i know ).

 

That’s what I’m worried about, because I feel a dirty filter couldn’t choke the pump that severely. I really hope it’s okay, to say the least. Definitely if the filter doesn’t solve the issue I’ll have to check fuel pressure.
I’m afraid I drove the car hard yesterday while I was testing it after installing the new pedal. I hope there wasn’t any damage done, but ever since we got the car on the driveway I haven’t cranked it since. It’s taken apart with the back seats removed and the filter housing apart until the new one arrives tomorrow.
Could the fuel lines be clogged? Is there reason to considering a draining of the fuel tank, if there’s even a way to go about it?

 

Oh boy, what kind of damage can you expect from a lean running engine??

 

I would highly doubt your fuel lines are plugged, the filter is there to catch all the little stuff so it doesn't build up farther down the line. If it was neglected long enough to have sediment under the filter then running some Seafoam wouldn't hurt in case your injectors are dirty. And I also wouldn't think your pump would be damaged from a plugged filter if it was a short term problem. If your pump is bad, it was most likely in spite of the filter not because of it. There are lots of tutorials on NAM and YouTube for changing a pump. Its not much different than changing the fuel filter, if you can change a fuel filter you can change the pump. There are several vendors on this forum that could help source the pump for you. Going back to injectors, if you have good fuel pressure, that would be my next suggestion. Again, I'm new to Mini's and have an R50 so I wouldn't know if they are serviceable or if your better off replacing them without doing some research.

I should probably throw a disclaimer in here. I do have a background as a service tech (for GM) but diagnosing a car several states away over the internet isn't the same as in person. I also don't want you blindly throwing parts at a car because some guy in NC said it might be a problem. My recommendations are based on a combination of past experience and what your posting. I am trying to help but I may not be correct. Changing fuel filters is regular maintenance, so your good there. But if your still having problems after that it can get very expensive without proper diagnostics to know your headed in the right direction.

And the statement about lean conditions being bad are a reference to broken pistons and in some cases completely ruined motors. Its better to have too much fuel than not enough especially in a boosted application. Not enough fuel and your piston gets too hot, bad things happen. Its probably worth a google. I split the block in half on a mustang July of 2018. I just got the car running again last week. It was overbuilt and over revved. The tune went bad and now it has a brand new motor . And no it should not take 2 years to swap a 5.0 but we had a kid and bought a house in that time on top of working a crazy schedule and life in general. Its a spare car/toy so not a real high priority.

Keep us posted on how you make out with it.

 

+1 fuel pump

mine went out slowly. Would get hesitation as you describe

 

Well, after the filter the car ran great to the gas station. Threw in some injector cleaner and as always filled up with 93. Car ran perfect on the way back as well. As soon as my dad turned the corner down the street on a test drive the car died.
Again it took forever to start. Eventually we got it in the drive way and ordered a new fuel pump. Installed it today and although the car started (after several tries) it’s STILL hesitating on throttle. Bought new spark plugs just in case, and tested the throttle body and BPV by running the car without the intake for a little bit just to see the valves open and close. I’ve officially ran out of ideas, so I scheduled an appointment once again with a reputable shop near me to see if they can diagnose the issue. Dropping $115 on Thursday morning, but at this point there’s nothing I can do.

 

Well that's terrible news! Did you test the fuel pressure prior to buying a pump? Or did it throw any codes? Keep us posted on what the shop says....

 

No codes, we didn’t test the pressure though. It’s definitely going off, I can hear it prime with the ignition on.

 

The trip to the shop last week left me buying a set of O2 sensors. Their diagnostics said that mine were shot, and after replacing them I should go back to have a tune flashed on to the ECU to compensate for the decat, which could be causing the car to run rich.
My issue is I ran the car a good couple of months without issues in regards to the test pipe and no tune. I really feel like it shouldn’t be necessary to upload a tune on to the car when running the mods I have, I haven’t made any adjustments to fuel.
I’ve went ahead and replaced the canister purge valve since that could’ve been a culprit, but still no progress. The car won’t accelerate past half throttle. Thinking about changing the MAP sensor soon.
I guess I’ll have to hear back from the shop how much a tune would cost. At this point I’m just throwing parts at the car and seeing what works.

 

I think with this one you may just need to start from the top with proper diagnostics. Do a compression and leak down test, and check your timing to make sure you didn't jump a tooth. You may also want to pop the valve cover off and see if there are any obvious problems under there, like broken springs or rockers etc. It will also give you the chance to check out the blower while its off. Hopefully someone else will chime in here but while running without a cat is less than ideal for several reasons I don't think it would cause the problems you are describing. Working on these cars is actually pretty easy and there are quite a few great tutorials on NAM and YouTube. There is a guy on YouTube that makes some really great videos that the good people of NAM mention quite often. I cant think of his name right now but I used his 'front end service mode' video to pull my bumper cover to repair some damage after hitting an abnormally large raccoon. I followed his instructions and it took me 6 minutes. All that to say you may enjoy doing your own wrenching and learning a new skill is always a good thing! Going back to the problem at hand, to put it very simply you need air, fuel, spark, and compression to make the motor run. To take it slightly farther you need air and fuel in the right proportion, enough compression, and spark at the right time. Mess any of that up and you no longer have a properly running engine. Please don't take this next statement wrong as I am sincerely trying to help as I have been there done that and learned the hard way from it. Throwing parts at a car with your fingers crossed is a frustrating waste of time and money. If being told that upsets you please accept my apologies, but I need to throw that out there because I see that happen way too often and people waste considerable amounts of time and money just to get fed up with the vehicle and sell it for a loss. If your o2 sensors are bad that could be the cause of your problem. If you have no cat you should see a rear o2 code even with a brand new sensor because the second o2 sensor is reading catalyst efficiency. The first sensor should be feeding the ecm your afr and the majority of the fuel trim (as far as o2 sensors are concerned) should come from that upstream sensor, and not having a cat shouldn't upset that too much assuming there are no other problems with the car. Some cars do use the second o2 sensor for more than just monitoring the cat but as far is MINI's are concerned, I don't know the extent of their role.

I read your last post several times and cant figure out if you have actually replaced the oxygen sensors yet or not? Please clarify that. And if anyone else that is more familiar with MINI's as far as how they respond to removing the cat, please feel free to share your experience

 

Did you ever get a diagnosis back for this? I think I’m going to have to go that route as well. At a loss for words because I just bought this mini because my other one **** the bed.