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Discussion Starter · #1 ·
Hi I’m getting random misfires on Mini Cooper R50 2003 Base 117,000 Miles.
I did a service changed oil, oil filter, air filter and plugs hopping this would cure the problem, no such luck
Connected the Autocom diagnostic tool and noticed there is a screen which monitors cylinder misfires above 200 rpm While monitoring at idle no misfire were detected however if the raise the rpm to 2000 the monitor starts counting misfires on all cylinders, I can’t feel or hear the engine misfiring but when the monitor gets to a certain number of misfires the check engine light flashes and shuts off one of the cylinders which you can feel
I’ve checked the fuel pressure and that is ok, I removed the vacuum line off the fuel pressure regulator and the pressure rises so the regulator is ok, no fuel leaking from the fuel pressure regulator vacuum connection.
I was checking the camshaft position sensor and left it disconnected and the misfire stops, Even at 2000 rpm no misfire Does this mean the camshaft position sensor is bad or is it not possible to measure misfires while the Camshaft Sensor is disconnected
The following has been checked
Spark plugs and leads have been replaced
Coil pack has been checked, swapped with a known good one issue still remained so swapped back
Throttle body cleaned and tested
Throttle pedal changed
Replaced PCV valve and Map Sensor
Repaired a few vacuum leaks
Any assistance would be greatly appreciated Regards Assad
 

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Discussion Starter · #2 · (Edited)
A bit more information
The above Misfire issue is when the car is parked up
While driving the misfire issue is slightly different and only happens above 3000 rpm, for instance driving on the motorway at 3000 rpm off throttle the monitor starts counting Misfires on all cylinders as soon as the throttle pedal is pressed the monitor stops counting misfires let off throttle starts counting misfires again
While it’s detecting misfires you can’t hear or feel the engine misfiring until it throws a check engine light and shuts one of the cylinders down, then it drives rough.
Below 3000 rpm it doesn’t detect any misfires
Again if the Camshaft Sensor is unplugged no misfires are detected even at 3000 rpm

Regards Assad
 

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Discussion Starter · #3 ·
Update fingers crossed the random misfire problem looks like it has been fixed
It was the cam position sensor.
Replaced the sensor and it seems to have done the trick, time will tell.
Thanks everyone for all your help
Regards Assad
 

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If it returns I would be checking my timing chain slack with the dummy tensioner, could be timing is out due to worn chain although predominantly a Gen 2 thing, at your mileage the chain may be past its sell by date.
 
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