What was found
ON TAXI R ENG HAD VIBRATIONS FROM 2.8 TO 3.3. WHEN ADDING TAXI THRUST VIBRATION INDICTIONS UP NTO 4.9 AND STARTED BEING VARIABLE- VIBRATION FELT IN AIRFRAME. AIRCRAFT RETURNED TO BLOCKS. (BTB). PERFORMED D.V.I OF RT ENG & FOUND UPPER & LOWER LPT COOLING AIR MANIFOLDS CRACKED. R & R UPPER & LOWER MANIFOLDS IAW AMM 75-26-01. OPS & LEAK CHKD GOOD. UPON D.V.I OF RT ENGINE FOUND STARTER DUCT SUPPORT ROD WORN & BROKEN CLAMP ON OIL SUPPLY LINE. R & R SUPPORT ROD IAW AMM 36-11-01 & REPLACED BROKEN CLAMP IAW AMM 20-11-00. PERFORMED ENG VIB SURVEY (TEST 7) IAW AMM 71-00-00. FOUND N2 SPIKING ERRONEOUSLY UPON DECELERATION ON EICAS INDICATION. DEFERRED VIB INDICATION IAW MEL 77-31-1. MAINTENANCE PROCEDURES C/W.