Symptoms
- Engine hard to start or runs rough
- Black smoke from the exhaust
- Noticeable power loss under load
- Filter looks dark, oily, or torn when inspected
Likely causes
- CommonNormal dirt and debris buildupGrass clippings and dust accumulate in the filter over regular mowing use.
- CommonOil-soaked filter from a tipped mowerTipping the mower incorrectly can let oil saturate a paper or foam filter.
- PossibleTorn or damaged filter elementA torn filter lets unfiltered debris into the engine, which can cause other problems.
- PossibleFilter overdue for seasonal replacementFilters degrade and should be replaced at least once per mowing season.
What to do
- Disconnect the spark plug wire, then remove the air filter cover and take out the filter element.
- For foam filters, wash in warm soapy water, let fully dry, then re-oil per the manual if specified.
- For paper filters, tap out loose debris; replace rather than wash if it's oily or torn.
- Check the filter housing for cracks or a poor seal that could let unfiltered air bypass the filter.
- Install a new or cleaned filter and confirm the cover seals snugly.
- Replace the filter at least once per season, or more often if mowing dusty or dry conditions frequently.
Tools and parts
- Screwdriver
Small engine air filterSearch: “lawn mower air filter replacement”
When to call a pro
Most mower shops will replace the air filter as part of a routine annual tune-up if you'd rather not do it yourself.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.