Rough Idle....

2006 Aveo Special Value Edition Sedan. 5 Speed. 295,000 miles and counting....

Approx. about 10,000 to 15,000 miles ago, back this past winter, I had this rough idle and I replaced the spark plugs, wires and valve cover gasket as the spark plug holes were full of oil. Rough idle went away. Shortly after I did a BG Fuel system injection cleaning as its free for me to do....

Fast forward to current day/millage. Rough idle is back. Idles around 800-830pms. If I tap the throttle, its jumps and smooths out. I just pulled the plugs and there was a thin coat of oil back on them. Nothing like before. I cleaned the plugs and wires and put it all back together. Rough idle is still happening. I'm thinking some oil got inside the spark plug....?

If this is true, is it normal for this to happen within 15,000 miles?

No codes.It does at random every 4,000 to 5,000 miles sets a lean bank one and a rich bank one.

Short term fuel trims are 0 give or take 2%. Long term are at 25%. Always has and never affected idle.

Ideas? Thanks!

What is the MAP sensor value range it idle?

3.8psi. It's not as bad this morning after I cleaned the spark plug Wells. But its still a ruff idle like a whole isn't firing completely.
Attachment 11072

3.8 is low. You can test the MAP sensor with a vacuum pump, if you have one. And some folks have also reported that the thin tube connecting the sensor was cracked and split, so you might want to check for that as well.