Hoping to get a discussion going regarding possible causes.

Vehicle: 2010 justa n12
CEL Code p302 cylinder 2 misfire

tested so far:
compression - even across all cylinders
coils - swapped coils, no change. Confirmed sparking
injectors - confirmed firing. Will do swap from cyl 1 to 2 next.

symptoms:
Base idle with no heater is around 750-800rpm. Clean clearly hear and see misfire due to engine shake and exhaust note. Engine smooths out from 850 - 1,500rpm when you can hear the misfire again from 1,500 - 1,900rpm and it goes away.

no smoke, spark plugs are clean. Car drives fine and is getting 36mpg.

Attached screens from torque

 

Update:
Cleaned both VANOS units. No crud or metal, but cleaned anyway.
Cleaned both cam position sensors. Had some crud.

N12 runs fine now.

 

Update:
Decided to replace the CAM sensors.
Can will start fine once warmed up. However, upon cold start, it would fire on 3 unless I unplug the one of the two cam sensors and she fires on all 4 again.

No more CEL and no codes either. Is it possible that the ECU is retaining the old fault? Unplugged the battery before I left for work this morning. Will see if any reset once I get home tonight.

 

How does one go about resetting adaptations?

 

I'm thinking the justa needs a reprogramming. If I let the car sit overnight, it starts with a misfire and won't pick up until I unplug and re-plug the cam sensor. Once the car is fully warmed up, it starts flawlessly.

I think I've driven maybe 40 miles so far doing this. No CEL and all values nominal. Car has full power and everything works.

Anyone know how long I have to drive before the DME relearns? Or I can't get it to relearn since I have to mess with the cam sensor on cold start and have to get a reprogram?

Any alternatives?

 

You need a scanner with advanced capability. Like Giotto Enginuity with the BMW mini advanced function. Or take it to a BMW specialist it the stealership and have them reset all adaptation.

That being said , it may not solve your issue. Have you checked the integrity of the wiring going to that one coil/cylinder that keeps misfiring?

 

No visual indicators of damage to the wiring for that one coil.

Looking at the torque data, it seems that I'm only picking up readings for the O2 sensor in Bank 1 sensor 2. Shouldn't I have a reading for Bank 1 sensor 1 as well?

My current drive status also shows an "Incomplete" status for the O2 sensor. Can this be the culprit?

 

Sorry to hear about your troubles. The engine coolant temperature sensor should report cold temperature at start -up which allows for the needed be fuel enrichment of a cold engine, otherwise the engine may misfire at startup.

The is sounds like carbon buildup on the intake valve causing cold start misfires.

​​​​​​Does this engine have direct injection?

 

Frenchie,

The engine is not direct injection? It is non-turbo NA.

Regarding the engine coolant temperature coolant sensor, during the course of my investigation, I would get a sensor low voltage warning which clears itself and the coolant temperature is displayed via diagnostic menu in the cluster.

Will take a look at the DME layout to see if I can find anything relevant.

 

Of course you should have signal from both banks.

But even if the 02 sensors are faulty, it won't cause a misfire. It will default to running rich for safety's sake and you'll get terrible MPG but the car won't misfire just because your 02 sensor is failing.

​​​​​If you've changed spark plugs and coils and that cylinder has similar compression to the other three, check the plug to the coil and it's respective wires. You might want to have a automotice electrician check that circuit's integrity, if you cannot.

 

If the wiring is bad, wouldn't the misfire continue after I unplug the cam sensor?

 

​​​​​​When you unplug the camshaft sensor, does more than one cylinder misfire?

What about the injector in that cylinder? BTW, how many miles on thet engine?

 

80k miles.

when I unplug the cam sensor, the misfire disappears and all cylinders fire as if nothing is wrong. Swapped the injector as well with same results.

Got another app where it picked up readings for the o2 sensor 1, but its reading at only .012mA

 

 

So, can we know your milage and any odd noises from engine on cold start because you have clear symptoms of timing chain being worn and timing being altered with Lambda and misfire errors. Do you have a mild 'death rattle'?
Ooops! 80K miles, just saw that. So, if not already done you are a prime candidate for timing chain replacement, a service item not mentioned anywhere by BMW. All engines require belt or chain replacement at some time and anywhere between 50-100k miles is suspect.
Stop throwing money at cam sensors, etc, these are probably reading everything correctly and telling you the timing is retarded due to chain stretch.

 

You've isolated all the obvious stuff, for sure. When you pull the camshaft position sensor do you get an error code? I assume you must.

 

Yeah, when I pull the sensor, I get the P0365 Camshaft Position Sensor Circuit 'B' (exhaust). It doesn't really matter if I take out the intake or exhaust cam sensor plug, the engine fires on all 4 and runs completely fine.

While I was checking the eccentric sensor, the plastic intake manifold (pre-filter) came right off. It seems that the mating surface isn't secure and there is a lot of wear. I taped it some to create a better seal and the engine sounded like it almost caught up without misfiring.

Really out of ideas at this point besides what I suspect to be the ECM. Can adaptations cause this if the PO kept running it on 3 cylinders for a very long duration? I can't get it to clear itself and at this point I've driven 100+ miles by implementing my temporary fix AFTER ignition.

 

Also noticed this screen. Don't know anything about emissions.

 

Here is a guess. The camshaft sensor, when unplugged, causes the computer to default to another algorithm for adjusting timing which is why all 4 cylinders then fiire correctly.

It's not the sensor because you've changed it. It's either that circuit or the engine computer.

Can you borrow another justa ECU from a friend?

Also check the ECU contacts for corrosion. I had another car with serious corrosion on the ECU pins and plugs. This caused all sorts of problems.

 

Pretty much checked all the connections for corrosion. Testing another ECU didn't cross my mind since I had assumed the car wouldn't start without proper pairing :O

Don't know anyone else with a mini, let alone convincing a stranger to let me yank their ECU out for a test LOL.

I'm going to try to chase the circuit and see if I could find a gremlin. Should that prove inconclusive, do you think a ECU reprogram would be better than clearing the adaptations?

About to go learn me some NCS Expert.

Thanks again for your insight. Having an extra mind seriously helps.

 

I wish I had more experience my friend.

Do you have a Bentley manual so you can map that circuit and test for continuity?

I have never swapped ECUs out of a mini. Only Japanese cars. So I don't know the procedure. Sorry. I can tell you that autoenginuity has a relatively limited number of actuation functions and only three adaptation reset options. It couldn't pair the new clock spring mechanism in my 2008 n14 for example so I don't know if it could pair a new ECU. I had to pay a BMW specialist shop $100 to pair the new clock spring & steering angle sensor. Which is to say that the dealer will have additional capabilities that the aftermarket doesnt.

If the circuit indeed has integrity you may need to ask a mini mechanic for advice. Go sneak in the back of the dealer and hand a mechanic $20 and ask a few questions.

 

Will definitely do so. Have not purchased the bentley manual but may consider doing so.

I've been getting most of my reference on the newtis.info site.

This one caught my eye though since your ECU swap suggestion:
" On replacement of the DME/DDE control unit note the following:

 

Yours would certainly not be the first to have a failed ECU, that's for sure. Maybe a used ecu isn't expensive.

​​​​​​Let me know if and how for able to check the circuit for continuity.

 

Going to leave the negative unplugged once I get home tonight and check back in the AM.

Granted, the vehicle starts in the AM and problem goes away (YAY). If not, I'm going to do a continuity test on all the wires in the engine harness from ECU to component most of tomorrow to the best of my ability.

Where the coil harness divides, I saw a glob of rubber that I didn't really notice until I started moving the tape around. Could be prior repair.

 

Wouldn't that be awesome if a failed past repair of one wire is the cause of all of this headache? That would be one hell of an easy fix.

Keep me posted.