engine noise on 2004 Ford Explorer

barely running ,engine noise in top end ,pulled intake & vale covers, when I trun engine over ,it locks up at one point,timeing chain on pass side gets tight then loose---should repair be tried or replaced, I understand special tools needed for cams

1 answer
These Engines do wear out the Timing Chains and depending on the exact type of 4.0 V6, there may be 2 chain sets. Only real repair is to replace them with new good quality chains and guides.

here is repair info site with online manuals

http://bit.ly/mitchell_repair_manuals_online