Craftsman M270 21 in 159 cc 3-in-1 Self-Propelled Gas Push Mower MECH-RUNS-ROUGH Error Fix: Engine Surges, Sputters, or Runs Rough

Error code MECH-RUNS-ROUGH on the Craftsman M270 21 in 159 cc 3-in-1 Self-Propelled Gas Push Mower means: Engine Surges, Sputters, or Runs Rough. The mower engine surges (rhythmic speed changes), sputters, or runs unevenly. This causes inconsistent cutting and is annoying. The #1 cause is a dirty carburetor from stale fuel. Causes: (1) Dirty/clogged carburetor — old fuel leaves varnish deposits that partially block the idle and main jets. The engine alternates between too-lean and too-rich as fuel intermittently flows through the restriction. Clean the carburetor thoroughly — remove the bowl, clean all jets and passages with carburetor cleaner and compressed air. Focus on the pilot jet (tiny brass jet) as it clogs first. (2) Stale fuel — drain old fuel and refill with fresh gasoline. (3) Clogged gas cap vent — the cap has a vent that allows air into the tank. If blocked, a vacuum forms that starves the engine of fuel. Test by loosening the cap while the engine surges — if it smooths out, the cap vent is blocked. Replace the cap ($5-$10). (4) Dirty air filter — restricts airflow. Clean or replace. (5) Fouled spark plug — causes intermittent spark. Replace. (6) Governor linkage issue — the governor regulates engine speed. If the linkage spring is disconnected, bent, or worn, the governor hunts for the correct throttle position, causing surging. Check that the governor spring is intact and properly connected.

The most successful fix is "Clean and Rebuild the Carburetor Thoroughly" (hard difficulty, ~60 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 ("Clean and Rebuild the Carburetor Thoroughly") is rated hard difficulty and takes about 60 minutes. Tools needed: Socket wrench set, Flathead screwdriver, Carburetor cleaner spray, Compressed air canister, Needle-nose pliers.

DIY cost: $10-$20. Professional repair typically costs $120-$180. 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-SELF-PROPEL (Self-Propel Drive Not Working or Weak), MECH-SMOKE (Engine Emits Excessive Smoke (White, Blue, or Black)), and 3 more.

Error code MECH-RUNS-ROUGH also appears on 6 other Craftsman models: Craftsman B210 27cc 2-Cycle Gas Leaf Blower (210 MPH), Craftsman M110 140cc 21" Push Gas Lawn Mower, Craftsman R105 30" 10.5 HP Gear-Drive Rear Engine Riding Mower, Craftsman T110 42" 17.5 HP Briggs & Stratton Single-Cylinder Riding Lawn Tractor, T210 46" Turn Tight, Z560 54 in 24 HP V-Twin Zero-Turn Riding Mower. The fix may vary by model, so check each model's specific page for tailored repair steps.