I have a 2007 R56 Hatch that my son and I purchased as a project vehicle. Veh is in great shape with 168,000 kms.

When purchased it ran very poorly misfired on cyl 4, no compression on Cyl 4 (Other cyls have 180psi) After much amateur troubleshooting we removed the entire engine and took to a rebuild shop where they completely rebuilt the engine.
We have now installed the engine in the car and after started it for the first time in 2 years.
It started right up and ran ok for 20 seconds but then seemed to start misfiring and running rough.
Here is the troubleshooting we have done in the last day or so:

• Installed a BlueDriver code reader and it says "engine misfire cyl 4"
• We checked the elect connection on the coil pack to ensure it is plugged in completely and it seems ok.
• Swapped the coil pack between cyl 3 & 4 but not the spark plugs. We restarted the engine and it ran similarily rough with same results on the Code Reader. Cyl 4 misfire.
• Next we did a compression test on cyl 4 and it came in at 180 psi. So it would seem that the cylinder is ok.
• Ran the engine with the spark plug and coil pack (from cyl 4) sitting on top of the valve cover looking for a spark when running but we did not see any
• All spark plugs are new with only a couple of hours of troubleshooting on them.
• The electrical connection on top of the coil pack does not seem to "click in" like it does on the other 3 cylinders.

The wiring harness going to the coil packs has clearly been worked on as evidenced by the electrical tape and hockey tape that has been used.

My gut feeling (i'm no mechanic) is that cylinder 4 is not getting proper power to the coil pack but i'm not sure where to turn next.


Evidence of wiring and electrical tape

 

I'm not a 100% but I think the spark plug has to be touching metal. I know when I was testing for spark, I touched that ground in the bottom middle of the valve cover. Then while the spark plug is out, make sure that the fuel injector is working. I was able to easily tell by the fuel smell coming out of the spark plug hole. If the spark plug isn't getting spark, then I would definitely pull that tape away with all the wires and see if something is chewed up of any sort. That's where I would start!

 

Was the cylinder head renewed during the rebuild? You could have a worn valve guide or valve stem in cylinder 4. I had worn guide in cylinder 2, despite passing compression and leak down tests that resulted in cyl 2 misfire. The valve seat was good. After engine and cylinder head renewal, I now run methanol/water injection to reduce the deposits on the valve stems.

 

Yes, the cyl head was rebuilt including all valves re seated, etc,

 

I'll try that and provide an update to this thread.

 

Okay, then yes, definitely electrical issue.

At one point during my rebuild, I traced the wire connections from the coil packs and grounds to the ECU to test their continuity and look for short circuits within the wire loom tower in the engine bay. While the coil pack wires checked out okay, this exercise of surveying wires later revealed broken wire insulation in the MAF sensor plug that were causing a CEL. All this to say that that wire loom experiences heat/cool cycles (being close to the turbo) and pull stresses (because it's in the friggin' way) during water pump repair and oil sender replacement/mods, that it's easy to imagine a wire or 2 fatiguing.

 

So I pulled some of the electrical tape from the wiring harness where the harness connects to the coil packs and here is what I have determined so far:

• There does not appear to be any damage to the wires even though there are multiple connections but the connections look to be properly heat shrinked, etc. So I am assuming this is original.
• There are 3 wires going to each coil pack off the main harness.
  • Each coil pack plug has the following
    • Black wire
    • Green wire
    • White (cyl 4), blue (cyl 3) , yellow (cyl 2) or orange (cyl 1)
  • It would make sense that the unique wire on each coil pack would control the firing sequence of the cylinders. Can anyone confirm this?
• Based on the condition of the wires and the fact that each coil pack has a black and green wire - that these wires must be operating correctly.

Here's what I'm thinking next

• Is there any way to check the connector ends of the coil pack wires for proper function?
  • ie. Is it possible to use a multimeter for any of this?
  • Is there a wiring diagram available?
  • It would seem to me that either the connector (that plugs into the coil pack) is faulty or my white wire is faulty.
  • Is it possible to move the electrical connectors from one cylinder to another? Will the firing order allow this?

some of the tape has been removed to expose - what look like undamaged wires.

 

Review this link. The coil wires trace to the ECU in my 2010 MINI Clubman S R55, pretty sure its similar for your year. However, I think the ECU board configuration changed between 09 and 10 (can someone confirm?).

There's a similar ​​​​page for the R56 (2007 to 2009) that describes a similar ECU short and misfire, but I can't yet find it.

 

Mini R56 update
Good day fellow Mini enthusiasts
After performing the troubleshooting above I sent the ECU, DME and KEY fob off to the ECU Pros in Pensylvania for testing.
They have now confirmed to me that the ECU and components are working 100% and are NOT causing my misfire problems on cylinder #4.

Here is a list of fault codes that were stored in my DME when they first hooked it up for testing (they have supplied me with this info)
DTC Description State
2D50 DME: Super Knocking History
277B DME: Combustion Misfires, Cylinder 4 History
2779 DME: Combustion Misfires, Cylinder 4 History
2F25 DME: Ambient-Temperature Sensor, Signal Current
2B64 DME: Intake Manifold, Unmetered Air Current
2F3F DME: Electric Fan, Activation, Power Stage 2 Current
2F28 DME: Ambient-Temperature Sensor, Signal History

A suggestion from the ECU test shop is as follows:
With misfires it could be that you have a possible air leak on your intake manifold. It could also be an issue with the fuel injector being partially clogged

Please note that I have replaced all of the injectors but have not looked at or tested the fuel rail for possible clogs.
Could there be a sensor on the intake side (fuel or air) that is telling Cyl #4 not to fire?

 

So, after all of the troubleshooting above I'm happy to say that the car is now on the road and running ok but certainly not 100%.
I am still dealing with the downstream throttle air leak, which tells me that there is unmetered air getting into the intake system.
I have replaced the Mass Airflow Sensor but the engine is still misfiring and reporting the same problems in the ODBC Scanner.
As a workaround, I have unplugged the MAF and the car runs (almost) perfect but I realize that this is not a permanent fix.

I've put approx 2,000 km on it since doing the above work and it runs decent.
I need to find a way to do a pressure test on the intake to determine if there is in fact an air leak.

 

On the N14 engine the PCV tube that runs from the back of the cam cover to the manifold can start to crack and let air into the manifold. I can’t tell from your pictures if you have the “cold weather” manifold. The “cold weather” manifold has a bunch of tiny vacuum hose connections between the cam cover and the manifold. Possible one of those has a leak… I would check that.

 

Does cylinder 4 misfire when the engine is cold?

Does the misfire go away when you disconnect the intake camshaft position sensor?

Did the repair shop replace the valve seats (not valve guides ... valve seats)? Did they replace the valves or did they grind them?

MINI Cooper N series engine valve seats are very shallow and tend to loosen up when the machine shop performs the 3-angle grind. Two things will lead to misfires caused by loose valve seats (1) overheating the engine, and (2) machine shop grinding.

 

The cylinder head on my current project car has been to the machine shop three times.

First time, to replace two cylinder 4 exhaust valve seats and one cylinder 2 intake valve seat; they also staked all of the other factory valve seats to prevent them from dropping. that repair lasted 10 miles.

Second time: Replaced cylinder 4 exhaust valve seats again. That repair lasted 4,000 miles; then three intake valve seats dropped

Third time: They sent the head to a Allied Cylinder head in Atlanta, GA to replace all valve seats with the deeper valve seats; my local machine shop didn't have a cutter small enough to cut the bore for these small valve seats.. See this post. They also had to replace three valves. The shop also went to a .007" press fit instead of the normal .005" press fit.

https://www.northamericanmotoring.co...lve-seats.html