What was found
ON RIA FLT 858, FROM ORD TO JSJ AT 2500 FEET AT CLIMB POWER NR 1 ENGINE VIBRATION INCREASED TO 4.0, ENGINE THRUST WAS REDUCED, AVM ALSO DECREASED. AIRCRAFT DUMPED 17,000 LBS OF FUEL AND AIR RETURNED TO ORD WITH NR 1 ENGINE AT IDLE. AFTER LANDING ACCOMPLISHED TROUBLESHOOTING PER 71-91-00, INSPECTION INLET, EXHAUST, MCD'S AND MAIN OIL SCREEN FOUND OK. LUBED CLAPPERS AND ACCOMPLISHED AVM SURVEY PER 71-00-00, ENGINE RUNUP NORMAL MAX AVM 1.2 AT TAKEOFF, EPR 537. AIRCRAFT OK FOR SERVICE.