2007 Mini Cooper Base model N12 engine 1.6l Dual overhead cam. Hello everyone, I am new here and need any assistance I can get. So, I'll just get into it. I have a misfire on cylinder 3 after the vehicle warms up. I have done quite a few things to the vehicle. I initially had a valve seat issue(it dropped out). I pulled the head off and had a machine shop replace all the valve seats. He inspected the rest of the head such as valves and cleaned it up. So here is a list of the thing I have done. 1. The head was then decked. 2. Installed the head with new head gasket and head bolts. 3. I also had a crack in the thermostat so that is new with the cross over tube to the water pump. 4. It has new spark plugs and coils. Have all been rotated without change in condition. 5. The intake to valve cover tube cracked therefore I replaced it. 6. Has a new valve cover pcv membrane. 7. New MAF 8. New VANOS solenoids 9. Replaced Timing chain and tensioner. 10. New downstream O2 sensor. 11. Intake gaskets are new 12. Swapped around the fuel injectors with no change in the misfire. 13. New Camshaft position sensors. 14. Replace O ring on the Vacuum pump.(Has good suction. Did a vacuum test.) 15. Did compression test all test the same around 180. All within 10%. 16. Ran Seafoam in the oil and gas. Lastly, the vehicle will run warmed up without misfire if one of the sensors are unplugged such as the camshaft position sensor of the MAF. This puts the engine in LIMP mode not allowing the camshafts to be adjusted. Let me know if you need anymore information. Any help would be great. Thanks in Advance. Edit: It only misfires at idle.
Hi and welcome to MA! You said you swapped the coil packs and the misfire did not move with the coil pack, did you try swapping plugs? Which valve seat dropped, was it number 3? Warm up the engine and do a compression check with it hot and see if it is different than when it was cold on number 3 cylinder. Off the top of my head all I can think of is ether when it gets warm something electrical is breaking down or once warm there is a compression leak. I am sure you have but recheck all the wires make sure they are clean and plugged in good. I don't think it could be in the timing. Please let us know what you find. Sorry I know this is not much help
Re: Thanks, and thanks for the reply. Yes I have swapped the spark plugs around and it is still in cylinder 3. It was the #4 cylinder that the valve seat dropped. I will give the compression test when its warmed up a try. I did today buy a new fuel filter that I am going to replace as soon as it comes in the mail. Either way I'm sure it needs a new fuel filter. There is one more thing that I noticed that I did not put in the first message which is pretty major. It was stupid of me not to include it. It only Misfires at idle. It runs fine otherwise. I have a diagnostic tool that allows me to view all the misfires when running. Thanks Again.
That could be a VANOS solenoids. I know you replaced it but they can cause misfire at idle after warm up. I have had new parts turn up bad so don't rule it out. Re check your vanos make sure the plug and wires are ok and clean.
Not at all familiar with Mini engine but I know in some cars with a variable intake valve lift feature -- a low and a high lift -- the engine can misfire during cold idle because one or both intake valve lifters do not switch from high lift mode to low lift mode when the low lift feature is enabled. In some operating situations the low lift feature can be activated when the engine is up to temperature. For instance at idle. Low lift reduces engine friction and reduce pumping losses. If one or both of the #3 cylinder's intake lifters doesn't switch to low lift this can result in a misfire. The valve or valves stuck in high lift mode let in too much air and the cylinder runs lean and a misfire is the result. The only solution if the lifter or lifters are not switching to low lift mode properly is replacement. If it comes to this both intake lifters should be replaced.