Okay, so here goes;
As I was preparing to depart in my 2000 SW2, I sat down and fired her up. She ran for about a half second, then died. When I hit the starter again, the engine spun quite fast, as if there was no longer any compression in the cylinders. And of course, it didn't run. Just spun. First thought; broken timing chain, but at 90k, seemed a little early. So,...
I removed the spark plugs and did a compression check - and Oh my gosh, 50 lbs? all 4 cylinders, 50 to 75 psi. Dang, that's not good! No wonder it won't run. Next thing, pulled the valve cover. Guess what, the timing chain was fine, tight, and oiled. Camshafts turned, valves opened and closed. Hmmmm.....
Put it all back together and noticed the engine sounded like it had some compression, maybe not as much as it should, but more. Held open the throttle and it started to fire off. After a little sputtering and rough running, (about 2-3 seconds), it smoothed out. Engine seemed to run fine, and on a test drive, it operated normally. Plenty of power and smooth. When I did another compression check the following day, I got 175 psi across the board! No wonder it runs now! The engine did pick up a miss, but a new set of plugs seemed to solve that. But the plugs didn't look that bad. But the number 4 hole was getting a little darker since the first compression check. I thought maybe the injector had plugged, but the new plugs and some injector cleaner in the tank seemed to clear that up.
So my primary question is, what on earth could have caused the loss of compression and then the (just as sudden) return of compression? Do SW2's have an emissions device that could have hung open and prevented compression from building? Could the throttle body have slammed so tightly shut as to have cut off the air supply sufficiently to prevent compression?
It was the same compression tester, and done in the same manner each time.
Any thoughts or ideas? the car runs again, just want to know what happened and what to look for as a possible future failure coming down the line...
Thanks!