Hello all - I too am a new BMW Owner/Forum Memeber. I bought a '97 318is with 108,000 miles a couple of months ago, and have been amazed by the driving experience. A couple of weeks ago my idle started being very rough. It still ran fine ( and got 32 mpg). I went to start it Monday, and it fell on it's face. I tried to re-start, but it sounded like the engine was turning over with no spark plugs in it, and would not fire.
To date I have changed the air filter, oil (Mobil-1) and oil filter (the filter in the car when I bought it was the dirtiest filter I have ever seen in a car), and spark plugs (Denso Iridium - could not find NGK)
I had to travel all week, so I started troubleshooting it today. First I made sure the cam was turning with the crank by looking through the oil fill hole - it was. I then pulled the plugs out 1 at a time and checked compression from cyl 1 to 4. 1 - 30lbs, 2 - 40 lbs, 3 - 70 lbs, 4 - 110 lbs. By now it started sounding like there was compression. I re- checked Cyl 1, and there was now over 100 lbs. I put the plug back in, cranked several times for 20 seconds or so. After a couple of minutes, it kept sounding more and more like it had compression, and it eventually started.
Runs better than ever, and while the idle isn't perfect, it is much better than before.
Any thoughts? Would hate to have it happen again while travelling and have it not recover...
Is VANOS hydraulic? could the condition of the oil when purchased and subsequent changing have broken some "crud" loose and temporarily screwed up VANOS?
I'm reaching - but I have never seen an engine lose almost all of it's compression, and then magically have it restored.
ghead Thanks all - sorry for the VERY long expanation...