Mazda recently installed my 3rd engine on my 2004 Auto. After a few weeks the engine sounded rough and examining the MAF sensor, I found oil on the plastic body. After cleaning with MAF cleaner the engine ran fine for another few weeks and got rough again. 2nd examination revealed oil again on MAF body, mostly on the side facing the air filter.

I have a standard Mazda air filter. Where could the oil be coming from?

 

You need to install an oil catch can (search the diy section for that). Are you overfilling your oil?

 

If you're not careful when filling the oil you can actually pour oil down the breather hose that connects back to TB area.

 

Catch can showing in the vent tubing drawing

 

I got lots of oil in that area due to a bad cat causing back pressure and blow back. Of course the CEL was on at the time.

 

I always had oily residue in the accordion tube even after I installed the catch can...
Residue collects in cooler weather but does not show up in the catch can.
Driving in the summer everything stays dry.

 

The catch can is junk.

Just follow the tube off the fill up pipe. Pull it off at the accordian tube. Cap it. Then put a filter on the tube from the filler.

You will never get oil again. PERIOD.

Now take off the accordian tube wash wish hose and dawn detergent.

Clean MAF.

MAF will never get oil on it again.

Forget the Half *** catch can.

 

^ Bad idea. Placing a filter on the oil-neck filler isn't going to do anything but spew any blow-back all over the engine bay.

You're much better off running it into a catch can and capping off the accordion tube. Or running a tube from the oil-neck filler directly out the bottom of the engine bay.