Hello, I've been trying to get my Mini Cooper R56 running for the last 3 months after I rebuilt my engine. I have an N16 engine and everything on the engine is brand new expect for the crankshaft, I put in the next size up pistons in (+0.25) over the stock size. I've checked spark, air, and fuel and all are good, but the engine continues to misfire on all cylinders the only codes I get are misfires. Whats strange is the car misfires a lot whens it dead cold but when it warms up it stops misfiring, but if I Rev the engine it will misfire on all cylinders. I've checked the timing three times using the ECS timing chain tool kit, and it looks good every time. The compression is 130psi on cylinder 1 and 2 and 135 on cylinders 3 and 4. My only idea now is that the fuel map in the ECU is incorrect for the larger bore. Any ideas or pointers are highly appreciated.

 

I just realized i put this post in the wrong location. Sorry about that

 

Use a scan tool to read the coolant temperature sensor with the engine cold. Does the reading make sense or not?

 

The scan tool says the coolant temp is the same temp as the ambient temp when the engine is cold. I also replaced the coolant temp sensor last week with a new one for ECS tuning since I thought it might be the sensor.

 

Are there any other DME fault codes besides cylinder misfires?

 

Misfires are the only codes I get.

 

Can you post all of the BMW misfire codes?

 

Here are the codes that I'm getting on the DME

 

Check for an intake air leak (unmetered air).

 

I did this test last week and I used a smoke leak detector on the intake and no leaks were found. It held at +10 psi for about an hour without leaking.

 

Also if I unplug the MAF sensor and run the engine it will still misfire. So I know it’s not an intake problem.

 

Did you reuse original spark plugs and coils?
After rebuild, did you reset all DME and VANOS adaptations and relearn Valvetronic Limit Positions?

 

I bought brand new coils and spark plugs from ECS tuning. I’ve done the reset all DME adaptions, VANOS adaptation, and limit position relearn multiple times through my scanner, it doesn’t seem to make a difference.

 

Unless I’m doing the procedure wrong in my scanner.

 

No scan tool errors appear when relearning limit positions?

 

nope it says it completes successfully every time. I can also hear the eccentric shaft rotating from limit to limit during the process.

 

Have you compared cylinder compressions when engine is cold versus warmed up?

 

I have not I’ve only done it when it was cold and got 130 on cylinder 1/2 and 135 on cylinder 3/4. I can check to see what the pressure is when it’s warmed up but I would assume it would be higher since it misfires less when warmed up.

 

Rings or valves may not seal well when engine is cold but may seal when engine is hot due to expansion.

 

Ok, I’ll check to see what the compression is when the engine is hot later tonight.

 

I re-rested the compression when it was dead cold and got the same result as last time 130psi-135psi on all cylinders. When the engine was warmed up the compression rose to ~140psi on all cylinders.

 

According to AllData anywhere from 8bar-12bar(116psi-174psi) is considered good as shown in the image below.

 

The minimal increase in cylinder compression of the warm engine versus the cold engine is a concern.

And I would expect at least 180 PSI for a warm rebuilt engine.

Maybe others have different opinions.

 

I'm just going to throw this in there because I just noticed I didn't put it in my original post. When the engine is cold and I try to start it, it will fire up and immediately and then stall out, I have to start the engine several times to get it to even idle without stalling. I also looked at the spark plugs when I was doing the compression check and they looked fouled out.

 

Larger bore alone shouldn’t cause that, sounds more like a vacuum leak, sensor issue (MAF/MAP, coolant temp), or ignition under load. I’d start there before blaming the ECU.