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37 Posts
Discussion Starter · #1 ·
Hi Guys

Love this mini, but this year have failed the MOT on emissions. There is more however, so I'll briefly run down what has been done to the car, and what I am still having issues with, and a whole bunch of questions!

Myrtle was Manic stage 2 mapped in 2017, akrapovic downpipe, AEM intake, Airtec intercooler, NGK one step colder plugs. I have the SPS switch, and generally drive on the "base" map, which throws a CEL for cat, gives me about 210 bhp. For last four years I have put it in performance 1 for the MOT, as this clears the CEL. Otherwise performance 1, 2, 3 are only used at weekends or longer road trips where I'm enjoying the drive. Once on the nurburgring 2018. There are other mods, but nothing signiticant to engine. Since then has flown through all tests, MOT, no issues. in 2020, I had to take her back a few days later after a good run, engineer told me this wasn't uncommon, especially as the car had sat outside not being used through lockdown for around 6 months. After warming her up and running a quarter tank through her in spirited driving, she passed easily.

This year, (end of 2021) same deal, failed first time, then again after the same warmup. Lambda was 1.04, and needed to be 0.97-1.03 to pass. So the enigne was lean at the exhaust. Other wise running generally fine. Vaccuum leak? PCV valve diaphragm had a split, I tried to replace it, but ended up with new valve cover as the replacement didn't seal well. This has solved the rough idle I had, and I suspect will now pass the MOT, but another problem has appeared, a bigger one. (thoughts on my confidence of passing MOT test welcome here)

Driving around locally to test (no MOT but I live in a very remote village in the middle of nowhere, I'm not driving to town or anything), and I get some misfiring. I'm driving along, and when on partial throttle or cruising below 2k rpm it hesistates a little, giving some throttle seems to avoid this, but 20 minutes into the journey it becomes full blown misfire. Engine seems like its running on 3 cylinders. Seemed like it was coils, so replaced all four coils (theyve been on for 60k miles) and new spark plugs, the one step colder ones same as when I had the map done. It runs great, feels great, until about 20 minutes in when this happens again. Restarting the engine doesn't fix it. Changing maps does nothing. When in this state, there is a strong smell of petrol around the car, and some codes indicating inhection cut, misfire random cylinders. Yesterday I left it on side of the road in frustration and took the dog for a walk to think, when I came back 30 minutes later, she started, and drove home as if there wasn't an issue. This morning, same, running fine (rough idle I believe is fixed due to new PCV and valve cover)

I'm looking for idea on how to diagnose. As I said I live very remote, have a garage and some tools, I'm happy to order parts, replace them myself, but dont think that just throwing more parts at it is the answer.

Next steps:

I have a new fuel filter (never been done AFAIK), oil and filter change, ready to do. Some googling has lead me to think this might be the thermostat? If so how can I check?

Using Carly I monitored some temps, I can see ambient 6degC, and engine/oil temps rising slowly after 5 mins idling, they're above 60deg, and climbing still (seems normal to me) and when engine stops, those temps fall again. Interior fans, heater all work well, I havent noticed them being less than super hot when on max, and they blow cold air when on minimum. This issue still keeps happening, and I'm at a loss as to what else I need to check, to know what is wrong and how to fix.

No local experts here (north coast of scotland) I was charged £960 to replace a clutch (just labour, i provided flywheel and clutch) because the guys didn't know my car, and it was a pain to do - 16 hours. So i'm hesitant to go see them and ask for help, only to find them go over what I have done already (all of the above) charge me hundreds and still not fix it.

Any help or advice greatly appreciated.

Couple other things to add: map was done on 97 fuel, but due to pandemic and this remote location I moved to 12 months ago, it has been three months on standard 95 E5 fuel before I finally found a local-ish (12 miles away) station that sells 97, so last two quarter tank fills have been 97, and I tried to run right down to fumes to make sure all fuel is 97. This is still happening.

37 Posts
Discussion Starter · #2 ·
Went back in for MOT again this week, and failed again.

So in last few months I have done:
Coolant change
Oil/filter change
Fuel filter change
Air filter clean and refresh (plum-coloured pod-style)
Valve cover replace (PCV valve issue)
Spark plugs
Ignition coils (all 4)

Here are the results from yesterday:

Natural Idle:
CO = 0.11 PASS

Fast Idle:
CO = 0.32 FAIL
HC = 173 PASS

Second Fast Idle:
CO = 0.15 PASS
HC = 146 PASS
Lambda = 1.100 FAIL

Overall she drives better than she has done in a long while, but there is still a very slight hesitation when cruising below 3k RPM. If I give it the beans, she really does feel pretty amazing, and as usual, but when partial throttle, cruising, its generally good, with just this very slight intermittent hesitation. Not undriveable, but noticeable when you've been driving the same car for 7 years. It isn't right. Before the plugs and coils, this hesitation would develop into full blown misfire, really rough idle and difficult to accelerate - limp home only, but not in "limp mode". Now its just this slight hesitation.

I had the flywheel and clutch replaced about 2,000 miles ago in august. The garage that did it initially told me the slave cylinder also needed replacing, so I ordered a new one, next day a different bloke (owner) of the garage called to say car was ready for collection. 20 miles later I had to get her recovered as the slave cylinder failed. They put the part that I had ordered on and since has been fine. That same job though also meant my steering was loose. They hadn';t tightened up the bolt next to the pedals that attaches wheel to rack, so was a small amount of play on-centre. I just tightened it up and carried on, but its made me think

If they didn't tighten that up correctly, could they have not re-attached my cat/exhaust and perhaps I have a small leak in between those components, i.e. small exhaust leak post-sensor, and thus high lambda? How could this relate to the hesitation? As its an N18, I dont really think its gonna be carbon build up, but am willing to get that done if necessary. Main issue is north coast of scotland, so its not like I can just take it to another garage, there are like 5 within 50 miles, and none of them are BMW/MINI specialists specifically, so not sure if anyone will know how to help me.

I am willing to pay money to get this fixed, I'm not trying to be tight, but given my location, I kinda need it to pass, so I can drive down south, take it to Lohen, or 1320 and get the correct diagnosis and correct fix. All the mechanics up here are used to dealing with weather damaged sh!t boxes and aren't really geared up for tuned engines and my expectation of understanding the problem and not just throwing parts at it.

The MOT tester yesterday initially said "its the lambda sensor" so I said "you think I need to replace the sensor?" he said, "well, we could try"

Hoping you experts might be able to actually help me here, as those guys just want rid of me to change tyres for locals and fob them off with uninformed diagnosis.

If anyone gives info that leads to my real diagnosis of the issue and an MOT pass... will receive a beer money token from me via Paypal, a generous one, I'm not joking, I really do need some help here!

2 Posts
Ok, I've had a think about the above and I'm going to provide a few suggestions.

I'd first rule out a leak in the exhaust system, as that could cause a high lambda. Just check for any obvious leaks.

My personal guess at the root cause is the high pressure fuel pump. Rough idle, misfiring, hesitation on acceleration are classic symptoms. If the hpfp is playing up then the engine could be running lean and causing the failure I believe.

I don't think the o2 sensor is the problem, I'd rule out the above first and swap as a last resort.

10,933 Posts
HC read high this tends to be a oil burning issues causing this,, so over a period of time this oil contaminates the cat and 02 sensors ,, the fuelling trim is controlled mainly by the cat and its sensors and mostly by the post cat sensor, these engines still bmw use these crap plastic oil rings and would also suspect valve stem seals not much better as they go by the state or even 50k engines i have seen with oil burning issues,
if were high pressure fuel pump would likely get a P2880 code common on them, also when you first start of the day they dont tend to start first time as air gets on to the pump due to seals gone cracked is what they fail with most,,
how much oil per 1000 miles is it using,, bmw say 1 litre to 800-1000 miles normal funny how vag group also say same about its fsi and tfsi engines,
if not using a lot of oil then replacing the cat and 02 sensors would bring readings down i would suspect as long as the engine is not burning a lot of oil etc,
hesitation 02 sensors very likely, also wear in the turbo can cause this, even a induction air leak can do same thing need to have the system smoke tested rule it out, it scraped through on HC and oil use will have some effect to the CO readings as well, another thing that can cause is timing chain related if over 60,000 miles it will be somewhere stretched , would also check the gauzes on the oil control solonoids for the vanos as if have dirt debris on them they will effect how the engine advances and retards its self ,,
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