my 03 Dakota with a 3.9 5 speed is showing code p0174

Question

now the code says its running lean on bank 1 but the truck is idling rough, exhaust really stinks,gas milage has gone down and is blowing black exhaust when accelerating.what usually causes this problem

Answer 1

P0174 Fuel trim lean bank 2

If there is excessive amount of backstroke coming out of the exhaust this is enough to set a lean fuel trim code,  And faulty 02 sensor thinking the system is lean can cause this condition , And since this engine has a MAP  sensor a vacuum leak can cause the MAP  sensor to deliver more fuel.

 Check the vacuum line right near the throttle body a vacuum leak here would cause a lean code as well as put more fuel into the system