* Positive Crankcase Ventilation (PCV) System Malfunction: This is the most probable cause. The PCV system is designed to vent crankcase pressure. A clogged PCV valve, hose, or other component in the system will cause pressure to build. The pressure builds until it exceeds the dipstick's ability to contain it, resulting in oil being forced out.
* Blocked Crankcase Breather: Similar to a PCV issue, a blocked breather (if the engine uses one separately from the PCV) will also prevent pressure release.
* Ring Problems (Less Likely): While the emissions test suggests this is unlikely, extremely minor ring wear could *contribute* to slightly increased crankcase pressure. However, this is less probable given the lack of burning oil and easy emissions pass. Severe ring wear would show up in the emissions test.
* Oil Pump Issues (Less Likely): A problem with the oil pump, such as excessive pressure, is less likely but possible. However, this would likely manifest as other problems as well (noise, poor oil pressure).
Troubleshooting Steps:
1. Inspect the PCV System: This should be your first step. Carefully examine the PCV valve itself (it should move freely), the hoses connecting it to the intake manifold and valve cover, and ensure there are no blockages. Replace any suspect components.
2. Check the Crankcase Breather (if applicable): Locate the breather and check for obstructions.
3. Check for Oil Leaks Elsewhere: While oil squirting from the dipstick tube is the main concern, make sure there aren't other small leaks that could contribute to pressure build-up by reducing the oil level.
4. Oil Level: Ensure the oil level is correct. Overfilling can contribute to increased pressure.
5. Consider a Compression Test (Less Urgent): If the PCV and breather inspection don't solve the problem, a compression test can help rule out more serious internal engine problems (though again, the emissions test makes this less likely).
In short: Start by thoroughly inspecting and cleaning or replacing the PCV valve and associated hoses. That's the most likely and easiest fix. If the problem persists, then investigate further. Remember safety precautions when working on your engine.
