Folks, I don't know enough to pin point the source of the problem so I have been replacing parts one at a time. When I went to a mechanic last year for help, I got charged too much for replacing two plugs and coils that made no difference. After doing the work, the mechanic drove the car and said it was fixed. It was idling rough when he brought it back. He then asked me if it was turbo, I said no, he recommended walnut blasting. Please help me do more due diligence...

The car has been running fine until last summer. I had to swap out a truck and leave the MINI on a farm for a month. It ran fine on the way back until I filled up the tank. As soon as I started her up, she ran rough. I then realized that I put in regular gas by mistake. I did that at least once before but it didn't impact the performance at all. Right now there's no problem starting her up. However, miles into any drive, once the traffic slows, the revs come down to below 2000 rpm, she starts vibrating and running rough. When she picks up speed again, it feels fine, but the CEL P0300 P0302 would come on and she would idle rough again and limp all the way home. I only drove enough to refuel with 3 or 4 gallons of premium. Now I stop taking her on longer drives.

Last week I replaced all spark plugs and ignition coils. 3 of the 4 plugs show oil so I replaced the valve cover gasket yesterday. The symptoms remain with the only code being P0300. Other parts replaced are vanos solenoid (intake and exhaust) and fuel tank breather valve. It is possible that rodents may have done some damage during the month that she was at the farm.

 

Thanks to advice by maybe maybe not in a different thread last Friday, I got a new scanner and paid for BimmerLink the next day. The more advanced codes point to under voltage in several aspects of the system. Will be replacing the battery today.

The current battery was installed in the beginning of 2020. As a backup car in the last 5 years, she was connected to a battery maintainer occasionally. I couldn't figure out why the symptoms seem to manifest earlier in a drive as I continued to fix more stuff. This may be the reason. No error codes related to the charging system, but will check alternator after the new battery is in.

 

A poor battery doesn't affect the car once started. A properly functioning alternator provides steady, consistent electricity at proper level for all operating systems.

I would suspect a fuel supply or PCV issue before plugs/coils. Those are isolated, easily traceable malfunctions that typically manifest consistently. I did have a car once that would misfire when hot, turns out there was a tracking line in the distributor cap that would conduct once the car heated up...but modern cars typically don't do this.

 

Appreciate your insights! I struggle to understand how things work together and am throwing darts in the dark. The codes gave me one more suspect to tackle. So far I have only worked on the easier items. Fuel pump/filter were replaced at maybe 160K miles. Fuel supply is the aspect that I am least familiar with and need a lot more reading on. 🤦

 

Codes from BimmerLink. I may be able to get the codes read by a shop using wired scanner and software on laptop.

Error Memory Date: 7/26/25 10:12:06 AM
Junction Box Electronics2 errorsA86E: UNDERVOLTAGEC914: PT_CAN_ID2A6_BEDIENUNG_WISCHER_TIMEOUTSwitch center, steering column1 error9E31: undervoltageEngine electronics5 errors27BA: 0x27BA combustion misfire, several cylinders27BC: 0x27BC combustion misfire, cylinder 22781: 0x2781 Misfiring, multiple cylinders277D: 0x277D combustion misfire, cylinder 227BF: 0x27BF combustion misfireTyre Pressure Monitor1 errorD115: Error CAN telegram timeout STAT_GANG_RUECKWAERTSStability system EBC_4505 errors5E30: Internal control unit: System voltage excessively low
5E31: Internal control unit: system voltage lowD367: CAN message: PT_CAN_TORQUE_3 ID: 0x0AAD366: CAN message: PT_CAN_TORQUE_2 ID: 0x0A9D365: CAN message: PT_CAN_TORQUE_1 ID: 0x0A8Instrument cluster1 error931D: BORDNETVOLTAGE, OVERVOLTAGE OR UNDERVOLTAGEHeating/air-conditioning control3 errors9C90: Control unit faultyE738: CAN message operation wiper button9C75: Under / over voltage

 

I reformatted your message to make it clearer.

I think you are on the right task to replace the battery with all those voltage errors. Swap the battery out, then clear the codes, and run the car to see if anything comes back. Then, reevaluate.

That being said, with 200k+ miles and random misfires, I might look at replacing the valve cover and PCV hoses...

 

Nice work. Now that you have some new leads from the BMW codes:
(1) Clear all codes from the JBE & DME (engine control module)
(2) Drive car around town for a while
(3) Then recheck for codes. Post and pursue any JBE & DME fault codes that repeat from first set of BMW codes.

 

Thank you for your help! I will report back later this evening. When the valve cover was removed for the gasket replacement, it looked to be in overall good condition, but I wasn't suspecting any faults with it. About PVC hoses, I need to locate them and check.

 

Thank you! Last Saturday it took me about ten minutes to retrieve the codes with the engine running. Then I saw a river flowing from roughly where the water pump is. 😂 Might only be able to drive for 3 to 4 miles. Scheduled to work on the water pump (pulley, tensioner, and belt) next Monday.

 

Whoops, I forgot about the coolant leak. May be best to avoid the drive.

And are you saying that all of the BMW codes have been cleared and that all returned after running the engine for 10 minutes?

 

I haven't cleared the bmw codes because nothing new was done yet. Will do after the new battery is put in.

The old OBDii was a generic wired unit with a display to show mainly the coolant temp. Normally the temp climbs up to 219 in slow traffic and would drop back down. If it keeps climbing to 223, that means the coolant level is dropping. I had an overheating incident back in 2019. Been carrying two gallons of distilled water and hose clamps in the MINI. 😂

 

Some or possibly most of the BMW codes you have recovered may be old non-active fault codes that were never cleared from the ECUs. If you clear all BMW codes and then run the engine for 10 minutes, then only a few BMW codes may return, which would quickly focus and simplify your diagnostics and ultimately the fix for the rough running engine. For example, you may not need a new battery.

 

I understand what you're saying. This is the first time I am reading bmw codes myself. 8+ years ago one shop told me that there were several misc codes not relevant to the issue at the time. I don't believe they were cleared. Battery is in now.

 

Codes cleared after the new battery was in. Started the engine and the idle was poor. Before I did all the work, she would at least start normally. 😨 Kept the engine running for 10 minutes and no codes came up. I chose the misfiring items for display on the sensors page, but they didn't work. Tried them on the dashboard page, didn't work either. What are the values that I should be checking?

 

I believe the base models only have an in-tank pump. You should be able to view fuel pressure using the Bimmer Link tool while the car is running.

PCV is integrated in to the valve cover, and when it's not functioning it will cause many problems similar to what you're experiencing.

 

Using a Launch scan tool, I'm unable to read fuel pressure for my 2012 non-S N16. Not positive, but I believe that scan tool fuel pressure readings may only be available for S models.

Driving the car may be required to set the fault codes. This may require waiting until the new water pump is installed and the cooling system is bled.

 

I haven't used Launch. Bought BimmerLink because the Scwaben/Foxwell tool that I had wasn't compatible with the GenIII/F series cars which my daughter and sister now have. I have used BimmerLink to read live data in those cars and you can see fuel pressure...but they're both S models.

 

Thank you! If it is the thick pipe covered in a fabric sleeve connected to the top left (passenger) side of the cover, I just need to figure out how to disconnect the other end at the intake manifold (?).

 

That is just the PCV hose. The actual valve is integrated in to the cover, and I don't believe it's a serviceable item on any of the Prince engines. You'll have to change the valve cover if you want to 'service' the PCV.

 

Need a more specialized scanner...

 

PCV Hoses:

There is one hose on the front of the engine that goes to the turbo inlet pipe. That hose is a heavier rubber, and is typically durable enough to not need replacement for the long life of the car.

The second hose on the back passenger side of the valve cover is the problem hose. That hose is thin plastic, and gets brittle with heat and age. They have a tendency to crack without detection. This is the hose:
https://www.ecstuning.com/Search/Sit...h/11157605186/

 

You linked the setup for the turbo/N14 motor. They have a 2011 N16.

 

Derp...

Here is the N16 rear PCV hose, Item #1 in the diagram:
https://www.ecstuning.com/Search/Sit...h/11157612996/

 

+1 thats the one Those have a little pinch clip and its hard to install when new. They will be tight.

 

Thank you! I There is small cover by the PVC hose that I am trying to pry open with a flat head... Had to stop because it feels like I might break it. Will order a replacement before breaking it. 😅