I have a 2004 xB with 47,xxx miles. Does not use oil. I get a misfire code for cylinder #1 (P0301) I have done a compression test and the results are (repeated 3x for each cylinder)

cylinder# PSI
1 105
2 200
3 195
4 195

Did a wet compression test on cylinder #1 with no improvement. I can feel the misfire at idle and at about 1,900 rpm. I can hear a faint caughing from the intake at idle. Does anyone have any suggestions on what I should check? I don't think it could be a VVT-i problem or timing because it is only one cylinder.

Thanks!

 

Wait, you dont use engine oil?

 

I found the problem. A leak down test indicated a leaky exhaust valve(s) on cylinder one. This is very strange to me. I have really taken care of this engine. Oil changes every 3,000 - 3,500 miles and has never been overheated. Never been abused (raced etc..) no modifications to the engine either. The timing chain was in good shape and tight. No reason for a valve to hit the piston. I am wondering if this is not the cause of a lot of the unresolved rough idle problems I see on quite a few discussions around the net.

 

Can't tell for sure til you pull the head off. May be the motor was over reved- that could have made the piston touch the valve. That's extremely low mileage to have internal engine problem due to wear.

 

Could be a bad valve seal or loose journal. At least you know it's in the head and not lower block. Unfortunately, regardless of the fix (new valve, new seal, or new journal) you need to remove the engine head. This can be done while the engine is still in the vehicle, though it's a tight fit to get the timing chain cover off and you will need to drain the oil and coolant.

The mileage should have it still fall under the 60k mile powertrain warranty, but I think it's only 5 year so you're over on the timeline.