Stalling while idling - in park

Hi, I'm new here. Decided to post because I have a 2000 Focus LX. It has 129,000 miles on it. Just replaced the motor mounts, and two days after I get it back from the shop it starts to stall as soon as I put it in park (can't even idle in park 3 seconds)

Sometimes the check engine light comes on, sometimes the oil light blinks.

I'm not sure if the mechanics bumped something or messed something up in replacing the motor mounts or if needing the mounts exacerbated the stress on some other parts.

I just replaced the mass air flow sensor around May of '11. Oil/filter was just changed and air filter is < 2 yrs old.

I've been reading that it may be an oxygen sensor or a hole in a pcv valve. But one thing is irking me. Whenever I took it to the dealership last spring to replace the mass air flow sensor, the mechanic told me there was a small tear in a hose (didn't say which one) and that he put tape on it.

Any ideas at all would be helpful. Thank you!

Certainly sounds like a vacuum leak. Some can be like finding a needle in a haystack. I would start with the PVC hose. I know they are a constant problem with the Focus. Had the same with my 2002. Replaced many things before I found a needle sized hole in the bend on the hose.

Maybe idle air control valve, looking to replace mine on 2002 focus. Will not idle or stay running.