Re: 98 Windstar;Engine oil in air cleaner tube
Make sure the intake is tight and secure. Next, check the filter if you haven't done so and replace if necessary. If it is clean and the intake is secure, then I'd suggest cleaning the throttle body. Remove the unit and all applicable sensors. If the TB is oily, then you've found your culprit. Spray the TB with TB cleaner, wipe with a clean dry rag and then reinstall. Take photos if necessary or if you don't have a repair manual.
Perhaps others will chime in with other suggestions on what it could be.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!