I rebuilt a motor for my sons 2010 Mini Cooper Base model about 70k ago and it ran like a champ till the plastic pipe on the intake side of the motor cracked and he overheated the motor dropping # 4 valve seat. @$^@$#%^@# That poor kid has the worst luck. He just paid it off.

To save him some money I headed to the yards and found a savaged head and rebuilt it... cleaned, faced it, new valves, lapped to the seats, valve seals, (it is good to own your own machine shop)

Bottom end got new pistons, rings, seal, bearing... ebay kit (don’t buy it, see below) I rebuilt it and put it back in the car. He lives in an emissions testing area and the rebuild kicked a check engine light or he would be driving it now. It runs great and I would road trip it across the country right now.

The motor runs great, and it is on its second oil change. On startup, it has a ruff idle if the motor is warm and kicks the listed codes below. Once running and it is done with testing, it idles clean at 800 to 1000 rpms. Durning the 30 to 45 start up checks it is all over the place 400 to 1800 RPMs sometimes it dies but starts right up. Again, only for the first 30 to 45 second startup the motor is up and down the rpms, thinks about stalling and sometime does.

If it is a cold start, it great, no issues. Runs normal like it should is up and down but not as bad. 30DegF and below. 10W30 oil

What I have tried:
Compression 190,187,191,190 and all four hold that pressure
Moved plugs, moved coils, Vanos solenoids moved and replaced, O2 sensors changes (had O2 light and fixed),
New NDK plugs
New cam rings seals for the oil passage vanos solenoids to gears for the exhaust only. When I put it together the exhaust where reuse plastic ones... the intake are cast and looked good going together.

All this makes me think it is a low oil pressure during startup getting to the intake VVT gear. If I revive it to 2k for the 30 to 45 seconds it sometimes passes it testing and it runs without codes till a restart, the reason I think it is oil pressure leaking past the cam ring seals or the VVT gear? My thoughts are, it could be the cam rings seals on the intake side ... or the ebay VVT gear is bad on the intake side. Changing the cam rings seals on the intake side is a pain to get too. I am thinking of pinning the fly wheel, locking the cams at TDC, release the chain, and swapping the VVT gears or should I do the cam ring seals. Seals are $14 each X2 per cam.
The other thought is the vanos actuator, but that would have issues all the time. I also tested this by using a 4mm allen wrench in the back side to move it out of its normal position and on startup it will reset and retuned itself.


CODES:
P0304 #4 Misfire
2783 Misfire several cylinders
277B Cylinder #4 misfire
287D VANOS, intake actuator move


Kit used to rebuild and not an endorsement (shipping and comms suck): https://www.ebay.com/itm/405031079821
Issues with kit,

Rings were on the pistons, how do you size rings if they are installed
Wrong seals for the fuel injectors
Valve cover seal was not tall enough to seal and blew oil on startup. yes it was a mess.
Bearing are no name (expected this)
Did not include the sealant for block to block
No front or rear seals
I can go on but why...

 

Did you already try deleting the VANOS and DME adaptations and relearning the valvetronic limit positions?

You also may want to check the retang rings at end of intake camshaft:

 

Hpfp?

 

I am using Blue Drive code reader. Not sure it can delete VANOS and DME. Is there a way of doing that without the going to the stealer (pronounced Dealer)? Willing to invest into a better code reader but there is so much crap out there.

I did the move the VANOS actuator using the 4mm allen. I found it on one of the forums and I thought that would reset it??

If you have a "how to" .... Thanks in advance.

 

I did replace them on the exhaust and I thinking from the vid, I am on the right track. Looking for steps to delete VANOS and DME.

 

^This and ignition coils are worth consideration for the misfire codes.

 

For these^ functions, I use a Launch X431 pro elite v2.0 for BMW.

 

No HPFP on the non-turbo.
I had a cyl 4 misfire & was thinking HPFP as well. Turned out to just be a fouled plug.

 

Thanks for the correction.

 

Outlaw. I've been through exactly what you are experiencing. I'll bet you lunch I know what's going on. To fully understand, I have to explain two things about your engine. 1. How the eccentric shaft and the variable valve lift system works, and 2. How the throttle body works in conjunction with the variable valve lift system.

1. There are two intake valves on each cylinder, this you know already. The camshaft opens and closes the valves, but the eccentric shaft controls the amount of valve lift. Unlike cars without variable valve lift, the N16 engine computer (DME) controls engine idle by opening and closing the intake valves. In cars without variable valve lift, this is done with the throttle plate. On the N16, the DME can use the throttle plate to control engine idle, but it will only do so if there is a malfunction with the primary operation of the variable valve lift system.

2. Again, two valve per cylinder right? Well, at idle, only one of the intake valves is opening, and it isn't much (about 180 microns). How do I know this because BMW's TIS doesn't even mention this. I found out by experience. I'll wait until the end to tell that story. I had the exact same problem ... a hot idle misfire in cylinder 2 on my N12. Like you, the cylinder head had already been to the machine shop; in my case, twice. So as I was looking for the root cause to my problem, I put a Starrett precision straight edge on the eccentric shaft and found the lobes on the shaft (two for each cylinder) are not symmetrical, they are staggered. Think of an old progressive carburetor where one throttle valve would open, but the second wouldn't start to move until the first was fully open. Well, that's the way the valve lift system works. The valve (for each cylinder) that is closest to the front of the engine opens first, the other intake valve doesn't open until the eccentric shaft rotates to about 140 degrees. This design improves fuel economy while giving your a nice boost at full throttle.

So, what's happening in your situation. When your engine is cold, your valve lift is a much higher percentage because of viscosity drag of the engine oil. Since the engine needs more fuel to overcome the viscosity drag, it gets more air, and the forward intake valve is open to a greater degree. Remember, the rear valve isn't even supposed to be open at idle. Next, as the engine warms up, the amount of valve lift goes down because the engine needs less fuel and the DME will keep the engine running at stochiometric (reduced valve lift). If the valve seat in your number 4 cylinder is loose, it will slip down just enough that the valve lift can't overcome the amount that the valve seat has fallen. This prevents the fuel air mixture from entering the cylinder, and you have your misfire. Initially, when this happened to me, I put a lab scope to observe the secondary ignition wave form to determine what type of misfire I had. I didn't understand what I was seeing until sometime later. See, the PV line on the wave form will increase (voltage) when you rev the engine; higher combustion chamber pressures means the coil has to produce a corresponding increase in voltage to overcome the pressure in the cylinder. You need more voltage to jump the spark plug gap when the cylinder pressures are higher. In my case, the PV line was near zero volts ... Why??? It was due to the fact that the cylinder was essentially running under a vacuum; the piston was going down on the intake stroke, but both intake valves were closed because of the loose valve seat. See, if an increase in combustion chamber pressure causes an increase in the PV line, a decrease in pressure will cause a decrease in the PV line. A vacuum in the cylinder is a serious decrease in combustion chamber pressure!

Now, how can you verify this is your problem. When your engine has reached operating temperature and is misfiring (use a scan tool to observe your misfire counter), disconnect the intake camshaft position sensor on the right side of the valve cover. This will cause a malfunction in the variable valve lift system and drive the DME into its secondary mode of operation (using the throttle body to control idle speed). With your scan tool, monitor your eccentric shaft position. It will drive up from around 20-25 to 171. This will cause both intake valves in your number 4 cylinder to have full valve lift . If this causes your misfire to go away. You've got a loose valve seat on the front intake valve in cylinder 4.

In my case, I purchased a project car '09 Justa cooper that was running on 2 cylinders. When I pulled the cylinder head, the valve seats in cylinder 2 and 4 had dropped. I took the head to my local machine shop, and reinstalled the head. Within 10 miles, the cylinder 4 valve seats dropped again. So the head went back to the shop. That repair lasted about 2500 miles, but during that 2500 miles, I was experiencing the same problems you are describing. I ran compression checks (all good), leak down tests (also good), Moved ignition coils, changed spark plugs, etc. Still I had this misfire in cylinder 2, but only when the engine was hot. I connected my lab scope; again I was baffled; The spark line looked good, but I didn't understand why the voltage was so low. As I kept driving the car, it finally catastrophically failed; I dropped seats in cylinders 2, 3, and 4. One seat in cylinder 3 cracked and almost broke into two pieces.

How did I fix it? I took the head back to my local machine shop, and they sent it to Allied Cylinder Head in Atlanta, GA. Allied has the cutter for these smaller valve seats.

Allied installed these deeper SBI valve seats. Notice how much deeper the SBI valve seats are.


Here are the part numbers.


Here's my damage from just one of my cylinders. Notice where the local machine shop staked the valve seats to prevent them from dropping; it didn't work



Good luck; IM me if you have any questions. Again, your misfire isn't because you don't have good compression; it's because the fuel/air mixture can't get into the cylinder.

 

SO where I stand with the rebuild.
I changed the Cam shaft seals on the intake side and the VANOS solenoid on the intake. Tested it with 12 volts and an old wire harness plug. It was hit and miss. Frist time I found one like that. Normally they work or they don't. So far, no more VANOS codes but now it will not start. Well, I got it to start but had to feather the throttle 1-3K to keep it running. Then I couldn't get it started.

Back to basics:
Pined the Flywheel, check the cams ??? all is good there. I was worried I might have @$#% it up but timing is good.
Compression is good on all 4 cylinders.
Also, borescope all four, not happy with the ring markings on the cylinder wall but I am sure it will get better after they seat.

Pulled codes, now have a P0100 & 2B51. (also had P115C & 2B56 Once) I tried a new MAF sensor, and it will not start, Tried another Throttle body and still no luck.

At that point I just needed to walk away. At this point I am looking for a broken wire or I have a hell of an intake leak. Looking for readings of the 4 wires going into the 5 pin plug for the MAF.

 

Have you checked your 5 volt reference?

 

DME connector X60211 (53 pin)
9 - MAF ground (white wire)
40 - intake air temperature input signal (blue wire)
41 - Voltage supply, terminal 15 (orange wire)

DME connector X60212 (32 pin)
14 - Air mass meter input signal (yellow wire)

 

Yea ... none of that. I'm talking about your 5 volt reference from the DME; the car won't start without it. When you crank it over, does the tach move?

 

I just borrowed my buddies scanner. MAF is giving indication of working. Tack is spinning up when trying to start.

Time for basics:
I smell fuel and plugs get wet after trying a couple of times.
I have compression
I've checked the timing. Pin flywheel, cam locks on.

Is there an easy way to check for spark? What would cause no spark..... Crank sensor?
The starting runs and it sounds like it would start but it doesn't kick over.

I tried starting numerus times. Because it hasn't started, I get no codes. I haven't gotten into the test pages on the code reader....

 

Great, the tach signal comes from the crankshaft sensor.

Yes, pull one spark plug and connect it to the coil. Connect a jumper wire from the ground of the spark plug to a good engine ground. Watch for a visible spark while a buddy cranks the engine.

 

You might want to arm yourself with some knowledge.

Scannerdanner.com (Paul Danner) He teaches diagnostics. This might be helpful


Join Paul in his classroom as a premium member for $11.00 per month. You'll be interested in chapters 22 & 23.

 

I figured that was the next step. The leading question is what would cause no spark on all four. ECU? Is there a fuse for the COP power?

 

You know that ground wire that connects to the stud on the front of the valve cover ... right in the middle? If that's disconnected or the wire is cut somewhere, none of the coils will fire. Oh yea, in most ignition circuits you have to have a cam and a crank signal for the ECU (DME) to fire the coils. Since your tach moves, you're crank sensor is working. So, now you need to check your intake and exhaust camshaft signals. The DME probably only needs the intake cam sensor for coil control

Paul is great instructor. I had shoulder surgery a few years back, and completed his entire course while I was on the mend; I got his book from AESwave.com so I could follow along.

 

That ground has some damage, but I thought it was still grounding. I will check that next. It would make sense as every time I pull the cover; it could have given up the last final strand of wire. If that fixes this. hahaha I've looked at that !$%^!@#$% too many times.

 

Cranking the engine with the valve cover ground disconnected has the potential to damage the DME. But definitely check for spark at the plugs first.

 

How would a disconnected ground on a secondary winding damage the DME driver on the primary side? Please explain.

 

It's a common issue...

 

At 1:29 he says the coil will ground through the computer but he doesn't explain how that would happen. The coil has two windings ... the primary and the secondary and it's a ground-side switched circuit. I would say that with the ground wire disconnected, the energy from the collapsing primary winding has no place to go, so it back feeds through the primary coil and fires the coil driver circuit.

Thanks for sharing that video. That guy is performing microminiature repair; did you notice the microscope? He's actually making repairs on the circuit board. Lots of very expensive equipment!