My 2003 RR 140000 miles with the 4.4 BMW engine timing chain guides failed and the engine quit. during the tear down I discovered the previous owner didn't do proper oil changes the oil sump was nasty with oil sludge and the timing chain guides and covers were also coated with sludge as well as the cylinder heads and valve covers , after I finished the tear down I used a solvent spray wand cleaning the engine to my surprise it came pretty clean with lots of scrubbing. I reassembled the engine with new chain and guides fresh oil and filter. Now I have an oil pressure problem! I did check the bolts on the oil pump they were fine I did pull the sump pickup tube and cleaned it, during initial start after reassembly the engine started right up everything seamed OK till I test drove it less than a mile the oil light came on and the engine started knocking i shut it down waited approximately 10 min i restarted the engine no light and no knocking I gently drove home oil light never came back on. I drained some of the engine oil and added marvel mystery oil thinking I must have some clogged passages over the next several days i started the engine and let it idle bringing the engine to operating temperature no oil light no knock! I took it for a second test drive I drove gently increasing speed slowly after I got to about 45mph the oil light flickered I stopped the engine and waited about 10 min and restarted the engine no light I headed home slowly increasing speed again and again at 45mph the light came on then went out with out stopping thinking that what i was doing was cleaning oil passages I continued for the next several days starting the engine and letting it idle to warm. third test drive did the same as before gently increasing speed I reached 70mph no light i drove approximately 10 miles no light thinking the problem solved I told the wife she could use the RR to go shopping explaining to watch for the oil light and what to do all went well during the first half of the trip no light how ever about half way home she was slowing for a turn and the oil light came on she stopped Immediately and called me I instructed her to let is set for 10 min and try it she made it home after the wait but as she pulled into the drive the light came on and she said the engine started knocking she shut it off! So I have parked the RR and not sure were to go from hear I am looking for suggestions what to look for next or am I looking at an engine tear down rebuild or did i screw something up during my cleaning and reassembly of the timing repair Sorry for the long post! any help would be appreciated Jimmy