2009 Polaris Sportsman 850 XP EFI EPS Service Manual, Page 152Get this manual
ENGINE TROUBLESHOOTING
Engine Spark Plug Fouling
Restricted air filter (main or pre-cleaner) or breather system Improperly assembled air intake system Restricted engine breather system Oil contaminated with fuel Fuel quality poor (old) or octane too high PVT system calibrated incorrectly components worn or mis-adjusted Restricted exhaust Spark plug cap loose or faulty Incorrect spark plug heat range or gap Weak ignition (loose coil ground, faulty coil, or stator) Low compression
Engine Idles But Will Not Accelerate
Spark plug fouledweak spark Broken throttle cable Air intake obstructed Air box removed (reinstall all intake components) Reverse speed limiter limiting speed Incorrect ignition timing Restricted exhaust system Camshaft worn excessively PVT not operating properly
Engine Has Low Power
Spark plug fouled Cylinder, piston, ring, or valve wear or damage (check compression) PVT not operating properly Restricted exhaust muffler Camshaft worn excessively