Catalyst System Efficiency Below Threshold (Bank 2) and system too lean?

Question

I have a 99 Ford Contour V-6> Although it is fun to drive but it always giving trouble. The car come up with 4 code:System Efficiency Below Threshold (Bank1, Bank 2) and system too lean(Bank1 and 2). After i saw this appear, i change both upstream O2 sensors, but it doesn't seem to help. My question is " are there one component failure can cause those 4 code to come up at same time??"

I have recently change to K&N air filter, is it related??

I was thinking about the DPFE sensor or MAF sensor or EGR, is it possible??

Answer 1

Some of the reasons for system eff. below threshold is:
Malfunctioning ECT/CHT
· High fuel pressure
· Damaged exhaust manifold
· Cylinder misfiring
· HO2S wiring concerns (shorted or chafed, bent pins, etc.)
· Damaged exhaust system pipe
· Damaged muffler/tailpipe assembly
· Retarded spark timing
Damaged Catalytic Converter:
· Use of leaded fuel
· Oil contamination/consumption
· Silicone contamination (sealants/cleaners)
The first thing I would do is install a fresh, gapped set of original motorcraft spark plugs. Then check the entire exhaust sys. for leaks. If you went to a kn filter, is the intake air temp sensor still connected? You may also want to change the ect ( engine coolant temp. sensor).

Answer 2

Ego sensors in back of the catalyst converter, or the converter itself

Answer 3

Well if you had no codes before you changed to a k&n filter than that is probably the problem.Yes one thing wrong can cause numerous codes.good luck

Answer 4

chang fuel filter if to lean the to much air not enough fuel and also fuel pump and sending unit and your caty might be filed with dirt yes dirt supprising but yea because friends grandam done it

Answer 5

the other answers are very possible, but i see a lot of collasped vaccum hoses or vac. leaks cause same problem. check pcv valve hose