Volkswagen Repair: oil pressure light, low oil pressure, oxnard st

Question
1990 4 cy jetta.

Thanks for service.  Two quick question.  Oil buzzer goes off when engine is warm. I replaced both sensers, but will change oil to 20/50 (i recently had an oil chg and i susspect they put in a lighter weight - car has 220K).  The question, which may be related:

when the car in idle in the drive way, if i remove the oil cap the car really seems like it's going to die.  It's a big difference with the cap on and cap off - should i be concerned?  Is this related to the oil pressure.  Also, i notice the directly below the right side of the block, there a quarter sized open hole on top of the transmission.  i can litterally see something turning when the engine is on.  It looks like a screw or plug could fit there.  Should this be plugged?

Thanks much.

Answer
Sorry to say, but it sounds like your engine is going bad. You probally do have low oil pressure from a worn out engine. What you are experiencing when you remove the oil cap is called"Blow by". This is combustion pressure escaping through the rings or valves. This is usually caused by a worn out engine. If you want to spend money, you can buy and install another oil pump, this might get your oil pressure up for a while. But if your engine dies when you remove the oil cap, this engine is in bad shape and has not too many miles left on it. I am Max's German Car located at 15020 Oxnard st Van Nuys CA 91411. Don't worry about the hole, the automatics have no cover for it and the manuels have a plastic cover but it is no big deal. No problems will occur if there is no cap.