2010 MINI Cooper S Clubman

After installing a known, good DME (ECU), to help troubleshoot a misfire on Cylinder 2, I started checking electrical continuity between the wire harness between Cyl 2 Fuel injector harness (orange and white wires) and the ECU. Good.

Note: this comes after several straightforward diagnostics that have been widely discussed on these MINI forum (e.g. switch coils, plugs; leak down/compression tests; timing chain replaced; valves and head removed inspected; timed according to specification of stamped cam insignia pointed up, valve cover, hose checks etc.)

After that, I checked the other fuel injector wires. Good.

Then decided to check wires of other components, and ran into an interesting phenomenon that does not make sense.

The pressure converter harness (unplugged) has an orange and white wire pair. Their continuity is good to ECU. VANOS (Orange + White wire pair). Good continuity. There is no crosstalk between the wires of these harnesses. However...the unexpected result...

When the Press Conv harness is plugged in, the Orange wire of the VANOS harness shows continuity with the White wire of the Press Conv at the ECU harness. I expect this is not proper and would wreak havoc on the VANOS while affecting the function of the pressure converter. For completion, the White wire of the VANOS harness still has continuity with itself at the ECU harness, and not with the white wire of the Press Conv harness.

I suspect the press conv has a short circuit, or is this unexpected result by design of a cryptic relay between the VANOS and Pressure converter? Such a relay is not visibly obvious.

Symptoms:
Rough Idle, triggers misfire code

Acceleration:
"Feels" (no proper boost measurement) the same as it did when I bought it new. Gas mileage about 25-27.

Other than rough idle, I would never have suspected any problem.

 

to help us help you, let us know what are the codes you're getting? what is the issue with the car? what is it doing now? how did you choose and prep the "new" DME?

 

P0302: Misfire cylinder 2

To restate:
Current Symptoms:
Rough Idle, triggers misfire code (same as before DME replaced)

Acceleration:
"Feels" (no proper boost measurement) the same as it did when I bought it new. Gas mileage about 25-27.

Salvage yard of known good DME from smooth running donor car. Prep: RPM Motorsport Ltd.

I guess my inquiry centers on the wire continuity phenomenon between a Plugged in Pressure Converter wire harness and the crossed over continuity (described in OP) of the Orange and White wires of the VANOS wire harness at the ECU plug. Does this indicate a short circuit in the Pressure Converter?

Hope this additional clarification and answers to "MiniToBe" questions were what are needed to help you help me. Best regards.

 

with this misfire, what else did you do other than chasing wires and replacing the DME?

 

ok i see what was done...I suppose the numbers are within spec...did you check the fuel injectors?

 

Hi MiniToBe, thanks for responding to this. I can attest, this has not been easy to troubleshoot. Yes, the injector itself was replaced. I essentially walked from the engine to the computer.

Examining the wiring diagram in Bentley's help sort it out the wiring phenomenon, but not the misfire.

Briefly, for those who are curious. The orange and white wires for each fuel injector go to a separate pin in the ECU (DME) harness so there is no crosstalk between those wires. I imagined a similar setup for all orange/white pairs. However, for several of the other switches, the power from the DME passes through pin 41 (orange wire) of X60231 harness and supplies power collectively via (X6821) to VANOS (see pg ELE-34), Pressure Conv, Wastegate of turbo, and 2 other units (each is an orange wire). I was unaware of this spice point (X6821) until after I removed more tape and plastic fascia. When one device is plugged in, it completes the circuit to an unplugged harness from white to orange. "Visual example" pin 1 (X60232) white--> plugged in switch--> orange--> orange splice point (X6821)--> orange at wire at harness of another switch. I am not sure which way the current flows Org to WS or WS to Org, but either way, the splice point was the answer to my phenomenon.

Bench tested the Pressure Conv and it operates seemingly okay by vacuum and electrical test.

Thanks.

My search for the source of misfire continues; it has not been trivial.

 

I know i keep going back, but sometimes you need to step back two steps to move three forward... Did you yourself do the diagnostics and repairs? I find it hard to believe that the wiring harness is bad specially if you see no cuts or corrosion on the plugs.
can you verify that all the plugs are pushed firmly and tight.

where are you located"?

 

In part. Went to a local MINI repair shop to just have them listen. $300 later I came out with a new turbo pipe (small split that I knew about, but wasn't causing problem) and summary sheets of past error codes--that I already knew about. At the shop, I was anticipating a diagnosis of a worn main bearing on cylinder 2, something more cryptic.

I needed to check the wires, through a process of elimination. I suspected the wires were okay, but I have sprayed water/soap to clean engine compartment, and needed to make sure. In addition, I have added an oil pressure gauge about 2 years ago, replace the thermostat, the feedpipe from the H2O pump to the thermostat and needed to move around the wire bundle...I just never know, if a wire got crimped or frayed during those events.


All plugs are tight, and wires are re-taped.

Michigan

 

I did my own diagnostics and the following results were verified within specs by the MINI repair shop: Compression, leak down, spark plug swap, coil swap. I was hoping the shop, with its more sophisticated diagnostic equipment, could detail something less obvious than what I found with my stethoscope, vacuum gauges and circuit back-probing with needles and clamps.

 

Ignition... check.
Injector... check.
What is fuel rail pressure with key on, engine not running? Should be ~5 bar.
What is fuel rail pressure at idle? Should be ~50 bar.

If all is good you've eliminated two of the three thing needed for combustion. Fuel and spark, all that's left is air. Compression is good. Leak down is good. So whatever gets in isn't bleeding off.

Was the #2 cylinder giving misfire codes prior to the timing chain being replaced and did anyone check for a collapsed lash adjuster on the number 2 cylinder while in there?

 

Thanks for the careful reading of my original post.

Fuel rail pressure is correct, 50 bar at idle and very high at WOT, can't remember exactly 700 bar (perhaps). Didn't check with the key on, engine not running. Will do to get a third pressure data point.

I appreciate your logic.

No, but something I recall. When #2 cylinder was NOT recording a misfire, even though it still ran with a miss, the exhaust cam was slightly advanced (based on lettering stamp on shafts) compared to intake. After I adjusted cam to spot on with the intake shaft, I started getting misfire cylinder 2. This is to the best of my memory.

I did not check this when I was in there, but nothing along these lines was obvious on disassembly and reassembly. This is easy to double check--removal of vanos gear and shaft is straightforward--only cost is vanos sprocket bolt and 2 h.

Other diagnostic result I should add:
1) Engine runs noticeably different when coil pack wires are removed one at a time from Cyls 1, 3, 4, but not much change in engine rpm with removal of cylinder 2 wire--this is what prompted new DME, thinking that it might be a faulty coil pack driver. The harness "looks" okay, but I will get out a magnifying glass to look in there on weekend to see if something is bent/broken.

2) Engine misfire rate is more on cold start up, less after it warms, but still misfires.

Again, I appreciate your logic. All the best.

 

Solution:
After doing obvious diagnostics and adding replacement parts, only when I replaced the engine and cylinder head were all of the problems solved (zero oil pressure and misfire ). The place where I bought the short block engine accepted the core and informed after teardown it was indeed a worn bearing that caused the oil pressure issue.