I have a 2011 base Cooper. Catastrophic damage to head with intake cam breaking caps and spitting out an intermediate lifter/roller. Replaced the head with an N12 head that had been freshened up from a machine shop. Valve seats were done and new seals. I checked with machine shop and they say they would have checked also the guides while doing the valve seats. It ran okay at first but had codes. In this process of trying to eliminate the codes, a shop did some testing including compression checks. Everything came back good. It ran like dog crap after it came back from the shop, misfiring like crazy and basically not drive able. The shop specializes in minis and theorizes that the misfires are caused by worn valve guides. Before I pull the head back off, I want to get some opinions of what else I could check. 78,000 miles. The shop said it was in cylinder number two and stayed there when swapping other parts. I am getting misfires now in multiple cylinders. Any thoughts?

 

My cheap diagnostic tool shows the following codes; 27BA - Voltage excursion O2 sensor before cat bank 2; 27BB - Camshaft control exhaust, bank 1; 2781 - Camshaft sensor, inlet bank 1;
2771 - Combustion misfires, cylinder 1; 2B84 - Intake Flap, signal; 2773 - Activation, tank-venting valve, bank 2; 2782 Camshaft sensor, exhaust, bank 1; 2772 - Tank venting valve, output stage; 27BC - Function camshaft control, exhaust, bank 2; 277D - Battery Voltage.

My regular ODBII diagnostic tool only shows P0301 Cylinder 1 misfire and P0300 Random cylinder misfires.

 

The plot thickens....found out the shop that "diagnosed" by Head Problem changed all the ignition coils without notifying me (or charging me). I think they put in used ones that were lying around the shop. Despite whatever actual problems I may still have with this head, the car ran more or less fine, just had a CEL. My plan is to confirm timing and swap in some known good ignition coils. I have no idea about the Tank venting and the intake flap. These cars are really a handful for a shade tree mechanic like me.

 

My guess would have been cam timing, since the head was off. If they reused the cam gear bolts, might not have been able to torque properly. Might be worht it to get new coils on there, too.

 

Since it ran ok a first, then like crap after the shop screwed with it, coils are a safe bet. You did not say why the shop replaced the coils.

However, clear ALL codes and retry with a beefy battery charger on the battery at all times as a dicey battery can wreak havoc with Mini's DTC logic. Experience has shown that the coil failure detection logic that trips the bad coil DTC is not worth a $h!t and will often fail to detect a bad coil. Overall Mini's OBD II software is really crappy compared to other cars I've owned.

For what it is worth the Bosch branded coils have been the most reliable I've used.

Other options you should hope are not possibilities.....
FYI from Google:
How do you calibrate valvetronic?
Basically you reconnect everything, turn the car ON (don't start engine), and wait. You should here the car going through the "self test/calibration" on the valvetronic motor. Wait about 30 seconds and turn the car off. Next restart everything should be ready.Jul 24, 2017

If the valves were ground and the seats recut then the Valvetronic actuator stored position is no longer valid for a given lift, and running like crap is the expected outcome. Even worse is if SOME of the valves/seats were recut/ground so that valve tip height relative the deck has changed for some valves and not for others.

If new coils and/or verifying cam timing fail to resolve the issue, then suspect that the shop that "freshened up " the cylinderhead didn't know FA about how to rebuild an N18 head.