My friend has 1999 Ford Explorer Sport 4.0/245 SOHC ,engine light stays on,he's replaced everything from the fuel pump to the IAC,an so on,however the exhaust manifold gasket an (Donut)gasket as well as fuel injectors are not new they have 150,000 miles on them,all vacuum lines are new,no other leaks are ocurring,O2 sensors have also been replaced,the vehicle still shows to be running lean,could it be the listed parts that haven't been replaced yet??

 

what codes does it have ??

 

Codes 71&74

 

I just recently replace all intake manifold gaskets and that did the trick, it really simple to do and cheap