MINI Cooper Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter · #1 ·
New to the group and hoping someone with deeper experience can help with an odd issue. 2009 U.S-spec gen II convertible, N12, non-turbo, 6-speed, 74,000 miles. Sets misfire codes for all 4 cylinders and random misfire codes. Has set P115c airflow code 3 times. At idle, the eccentric shaft motor turns back and forth constantly. The engine runs poorly at idle, better at higher rpms, sometimes feeling perfectly normal at higher rpms. With the eccentric shaft motor disconnected, I can manually turn the shaft and get the engine idle to smooth out completely. But of course it sets a limp home mode. Have run adaptation and everything is supposedly set, but problem continues.

A little background might illuminate the issue. The engine suffered a failure that resulted in coolant being dumped into the oil. The small casting plug at the front (timing side) of the cylinder head failed. I replaced the plug and flushed the cooling system and the block, running fresh oil and filters multiple times. Timing components all looked good, no indication of chain stretch or out of phase cams. Oil pressure appears to be good, the engine is clean. The engine was never overheated. According to the owner, it ran normally prior to the coolant event. What I'm struggling to understand is what's causing the eccentric motor to act in such an erratic fashion. There are no codes related to its function, or to anything else other than misfires and the aforementioned P115c. Ignition coils all test good. Injectors all test good. Compression measures 200psi across the board. However, #4 cylinder consistently shows sootier/darker spark plug color than the rest. Is this an electronic issue, or possibly a mechanical issue causing a system response that shows itself as described? Could collapsing lifters on the #4 cylinder and a resulting lack of intake flow to that cylinder cause the system to constantly adjust itself due to inconsistent intake flow? That could possibly explain the constant back and forth of the motor and the fact that no other codes are set. Would love to figure this out and hope someone might have some insight as to what to look at next.
 

·
Registered
Joined
·
9,605 Posts
the vvt steppa motor is designed to wind and unwind ie change the lift on the valves,, the inlet at idle is controlled more by the vvt motor than the throttle body ie based off the ecu and how ecu sees the signal voltages from the 02 sensors when in closed loop running,,, ie closed loop is when exhaust reaches 600c ie the temp the 02 sensors make voltage that gets sent to the ecu, and use to trim the fueling, its very possible you have a issue with number 4 that the 02 sensors are reacting to, ie a reactive fault where all sensors are doing what they should,,, would also check the spring fingers on the inlets,,, ie the ecu detects a steppa motor failure it will force a limp mode and shut the vvt down,, so fact its running still would make me wonder if fault is something else
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #3 ·
Thanks for your input Mike; I was hoping you'd see this. Sounds like you think I might be on the right path thinking I have a mechanical issue that's causing the electronics to constantly adjust in an attempt to correct?
 

·
Registered
Joined
·
9,605 Posts
i do a lot of vag stuff and stuff that has been heavily mapped and driven hard come across all kinds of faults caused by mechanical failure ,,, had audi rs4 the other day the idle would rev to 1500 revs then drop to 800 revs and do this 20 times over a 60 seconds time span, this car had been in to a few garages and had all kinds changed etc,, by time we had it it was also pico scoped and they could not understand why it was doing what it was,, they put a new 02 sensor upstream on it and this made it worse,, ha ha the clue in my book the new sensor was reading the 02 in the exhaust better with new sensor,,, then i done a misfire count with delphi found in 20 seconds 60 misfires on one cylinder,, done a compression all were ok,, then done a leak down test while inlet and exhaust manifolds off the engine,, bang there it was exhaust valve cracked,,, so what was happening the car would heat up and as soon as the exhaust reached 600c the car would switch in to closed loop running so both 02 sensors were dealing with fueling trim at about this temp the crack in the valve would expand and dumps air or fuel on to upstream depending on its stroke... mini engines do same trick and run lumpy and get rich to lean fault codes when do,, need to rule this out as they all go this way at some point
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #5 ·
Interesting. Ok, I'm going to see if I can measure/find some way to rule in or out the idea of possible lifter collapse or ... The thought on partial lifter collapse is prompted by a visual cue. With valve cover off, the #4 intake lifters appear to achieve a shorter actuation stroke, as in do not plunge as deep as the rest. Thanks for the input.
 

·
Registered
Joined
·
9,605 Posts
on the inlet the spring fingers that are part of the high lift mech should locate to the rear of the upright lifters in a squared groove and only just touch them by 2mm tops over hang so can slip out when do loose the high lift and idle control on the valves as such,
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #7 ·
The issue gets more interesting, and maybe swings back toward looking like an electronic problem? My attempts to confirm or dismiss lifter collapse were unsuccessful (didn't have the right measuring equipment), so I buttoned the valve cover back up so I could move the car. Started it up and it ran perfectly. Discovered I had inadvertently left the exhaust VVT solenoid disconnected. Connect the solenoid, back to running like crap. Disconnect, back to running fine. Apparently, with a solenoid out of circuit the variable lift goes into a default mode. The variable lift motor screws to full lift and stops. No variable lift, but it runs excellently. Now the question is, what's going on? There is of course now a fault code for the VVT solenoid, but none other than that.
 

·
Registered
Joined
·
9,605 Posts
exhaust VVT solenoid disconnected ,, there is not a vvt on exhaust side only the inlet side, do you mean the oil control valve for the vanos timing sprocket ie at front of engine round metal tube looking thing ie vanos oil control solonoid, or do you mean on top of rocker cover the two black sensors ie one for inlet cam and other for exhaust cam,,, those are cps ie cam position sensors,, when these go faulty get misfire or no start and also will get issue with timing as the cams sensors are used by ecu to control injector timings and coil pack timings and vvt positions and vanos positions,,
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #9 ·
Oil control solenoid on exhaust side, timing end of engine. There's another one on the intake side. 2009 N12 engine. Not the cam sensors, which are on the opposite end. If either CPS is malfunctioning shouldn't I get a fault code?
BMW-MINI-VVT.png
 

·
Registered
Joined
·
9,605 Posts
would suspect you have a vanos problem could start with the solonoid replacement, also would check voltage to it engine running it will normally jump around as ecu trims the timing to vanos,, clue might be if get 12v constant might indicate the vanos or the oil control valve maybe faulty or the oil control rings in the first camshaft journal bleeding oil away,,,
theory to this is this best done with a scope and see waveforms and see when ecu switches and sends oil to vanos sprockets to advance and stop sending oil to retard them back,, so if voltage dont drop then that would say ecu trying to advance all the time, like said best with a scope and also scope to cps and crank sensors as well,,, into some complicated stuff,
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #12 ·
Quick update: Although oil pressure didn't appear to be an issue, turns out it might be. Hovering around 5psi hot at idle, max of 30 hot at 3,000rpm. And oil pump is noisy. Could insufficient oil pressure be the culprit in all of this? Plan to replace oil pump and at least knock that out of the equation. Will post results, but will be a couple of weeks
 

·
Registered
Joined
·
9,605 Posts
Quick update: Although oil pressure didn't appear to be an issue, turns out it might be. Hovering around 5psi hot at idle, max of 30 hot at 3,000rpm. And oil pump is noisy. Could insufficient oil pressure be the culprit in all of this? Plan to replace oil pump and at least knock that out of the equation. Will post results, but will be a couple of weeks
very common reason for such issues hence why i bang on to people check the basics before anything else, ie oil pressure, compressions and leak down tests will rule out or rule in mechanical reasons being why it plays up,
 
1 - 13 of 13 Posts
Top