Craftsman Craftsman T110 42" 17.5 HP Briggs & Stratton Single-Cylinder Riding Lawn Tractor MECH-RUNS-ROUGH Error Fix: Engine Runs Rough, Surges, or Stalls

Error code MECH-RUNS-ROUGH on the Craftsman Craftsman T110 42" 17.5 HP Briggs & Stratton Single-Cylinder Riding Lawn Tractor means: Engine Runs Rough, Surges, or Stalls. The riding mower engine starts but runs unevenly, surges (rhythmic speed changes), sputters, or stalls during operation. This makes mowing difficult and can damage the engine. Causes (in order of likelihood): (1) Running with the choke on — after the engine warms up, push the choke to OFF/RUN. Running with the choke on causes a rich mixture that makes the engine run rough and smoke. (2) Stale or contaminated fuel — gasoline breaks down after 30 days, forming varnish deposits. Water can enter the tank from condensation. Drain the tank and refill with fresh fuel. Always use fuel stabilizer for storage. (3) Dirty air filter — a clogged filter restricts airflow, causing a rich fuel mixture. Check and replace the air filter every 25 hours of operation. (4) Fouled or worn spark plug — carbon buildup or electrode erosion causes weak spark. Replace the spark plug annually or every 100 hours. (5) Clogged fuel filter — debris in the fuel restricts flow. Replace the inline fuel filter. (6) Water or dirt in fuel — drain the fuel tank and carburetor bowl completely. (7) Blocked gas cap vent — the cap has a small vent hole that allows air to enter the tank as fuel is consumed. If blocked, a vacuum forms that stops fuel flow. Clean or replace the gas cap.

The most successful fix is "Replace Spark Plug to Improve Engine Combustion" (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 Spark Plug to Improve Engine Combustion") is rated medium difficulty and takes about 30 minutes. Tools needed: Spark plug socket (5/8 inch), Ratchet wrench, Gap tool, Torque wrench.

DIY cost: $10-$20. Professional repair typically costs $90-$140. Many homeowners save money by trying the top-ranked community fix first.

The Craftsman Craftsman T110 42" 17.5 HP Briggs & Stratton Single-Cylinder Riding Lawn Tractor has 8 other known error codes, including: MECH-BATTERY-CHARGING (Battery Will Not Charge or Hold Charge), MECH-BELT-WEAR (Drive or Deck Belt Premature Wear, Breakage, or Slipping), MECH-BLADES-WONT-ENGAGE (Mower Blades Will Not Engage When PTO is Activated), MECH-ELECTRICAL (Blown Fuse or Complete Electrical Failure), MECH-FLAT-TIRE (Flat Tire or Tire Will Not Hold Air), 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, M270 21 in 159 cc 3-in-1 Self-Propelled Gas Push Mower, 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.