When I removed my airbox I saw that the inside of the throttlebody was filthy, look like oil has been running there.

I have attached an image so you can see for yourself.
Is this indicative of a bigger problem or is it common?

 

have you been using oil!

 

No siree I haven't been using oil, as fuel anyway!
The whole cars insides are quite filthy from the oil-treatment the car got in autumn 2004, it protects from rust, finally gotten around to cleaning out my engine now. Maybe thats it? Though I dunno how it could have gotten in there!

 

Are you sure it's oil and not some type of rust solvent?

 

Not really sure what it was, I wiped it away and all thats left of it is that photo, I was worried it might be a serious problem causing it.

 

It looks as if someone has hooked up the PCV valve to the throttle body of some sort. Perhaps your throttle body is leaking coolant that need to be replaced.

 

Sorry, do I need to replace my throttlebody or the coolant?

 

I'm guessing that's unfortunately normal. I think it's from the PCV valve. probably due to "reversion" or some such scientific theory. same as on carbureted motors, the carb air horn gets oil-vapor-fouled. I'll bet your IAC valve (pintle) is also fouled. Mine was also fouled. had to use a lot of solvent spray (e.g. brakleen) to get it cleaned. but then it fouled again after a while. I think it's the motors' way of telling you time for a valve job or rebuilt. I suspect there was lots of oil "blow-by" due to bad sealing, either the valve-stem seals, or the oil-rings on the pistons. I'd guess this was typical for a high-mileage motor. mine had 200k+ miles on it before I replaced the heads (and disconnected the PCV valve). no smog checks here. Unfortunately, now I'm venting oil vapors to "the atmosphere", right into my cowl vent plenum and to the AC vents and the interior of the car. It's absolutely great.

 

I tested the PCV valve, i could blow one way and the other as well but it was much harder to blow one way. Should a funtioning PCV valve seal one direction completely?

Later this year when I am going to polish my plenum and runners I also planned to replace the gaskets there as well as on the valve covers. I hear that with the valve covers off you can check for carbon deposits that might clog and cause this behavior.