I'm replacing iacv and when I removed throttle body,there is oil behind throttle body in plenum,oil was also on back of throttle body..Is this normal??

 

That looks like a puddle, nope, not normal. There would be coking but not a pool.

Check your PCV valve is not jammed, pull it out and verify it is clean and freely rattles. Verify the breather tubes are clean and undamaged.

 

Ok,so in other words it's suckling oil in through one of the breathers or pcv?

 

Ok,I pulled the pcv and it does not rattle at all..Other tube are fine..spark plugs are clean..iacv was pretty clean..

 

It needs to rattle. Replace it. Pick up the grommet that the pcv plugs into too. Normally they get old and hard as a rock. Be careful removing it. It will want to crack and fall in the crank case. Just be careful.

 

If you have some throttle body cleaner spray, you may try to unstick the valve, but if it is overly gummed up or appears to be damaged/deformed, then you will need to replace. And yes, if the PCV is stuck open then the engine will ingest oil.

 

Thanks guys,I'm gonna replace it and cross my fingers! I'm a chevy guy so please excuse my stupid questions,lol..