Craftsman M270 21 in 159 cc 3-in-1 Self-Propelled Gas Push Mower MECH-SMOKE Error Fix: Engine Emits Excessive Smoke (White, Blue, or Black)

Error code MECH-SMOKE on the Craftsman M270 21 in 159 cc 3-in-1 Self-Propelled Gas Push Mower means: Engine Emits Excessive Smoke (White, Blue, or Black). The push mower engine produces visible smoke during operation. The smoke color indicates the cause: WHITE SMOKE — (1) Oil entered the combustion chamber, most commonly from tipping the mower with the air filter side down. Run the engine for 5-10 minutes; the smoke should clear as residual oil burns off. (2) Oil overfill — too much oil is being splashed into the combustion chamber. Drain to correct level. BLUE SMOKE — oil is burning in the combustion chamber continuously. Causes: worn piston rings, worn valve guide seals, or a damaged head gasket. On older mowers, this indicates significant engine wear. Check the oil level frequently. BLACK SMOKE — the engine is running too rich (excessive fuel). Causes: choke stuck in the closed position, severely dirty air filter (restricts air, making the mixture rich), or carburetor float stuck open (flooding the engine with fuel). First, ensure the choke is fully open/off after warmup. Then check/replace the air filter. If black smoke persists, the carburetor needs service. General: a small amount of smoke on startup is normal, especially if the mower sat unused for a while. Persistent heavy smoke during operation indicates a problem that should be diagnosed.

The most successful fix is "Replace Air Filter and Inspect Carburetor for Flooding Issues" (medium difficulty, ~30 minutes). Estimated DIY cost: $10-$20. HomeMD has 2 community-ranked fixes for this error.

This error is rated low severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Yes — the top-ranked community fix ("Replace Air Filter and Inspect Carburetor for Flooding Issues") is rated medium difficulty and takes about 30 minutes. Tools needed: Flathead screwdriver, Socket wrench set.

DIY cost: $10-$20. Professional repair typically costs $110-$160. Many homeowners save money by trying the top-ranked community fix first.

The Craftsman M270 21 in 159 cc 3-in-1 Self-Propelled Gas Push Mower has 8 other known error codes, including: MECH-FUEL-LEAK (Fuel Leaking from Mower — Fire Hazard), MECH-OIL-LEAK (Engine Oil Leak or Excessive Oil Consumption), MECH-PULL-CORD (Pull Cord Breaks, Sticks, or Will Not Retract), MECH-RUNS-ROUGH (Engine Surges, Sputters, or Runs Rough), MECH-SELF-PROPEL (Self-Propel Drive Not Working or Weak), and 3 more.

Error code MECH-SMOKE also appears on 1 other Craftsman model: Craftsman M110 140cc 21" Push Gas Lawn Mower. The fix may vary by model, so check each model's specific page for tailored repair steps.