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??" Because i was thinking about the MAF sensor....Help

The engine run just fine. I have changed to K&N filter, would it be related??

Answer 1

How does the engine run? V6 Contour/Mystiques were notorious for catalyst failures. Did the DPFE hoses blow off? If so, that alone is your confirmation that you have failed catalytic converters. The cause of system lean banks, #1 and #2 (P0171, P0174) are usually caused by a vacuum leak(s). Check for PCV valve, loose, cracked or broken PCV hoses, lower intake gasket leaks. Hope this helps.

Answer 2

Plugging Cats can cause the 4 codes on this vehicle or something blocking inside the exhaust... I've seen them run good but performance was very lacking on hard acceleration... Usually to pop the DPFE hoses off you have to have some serious backpressure to the point that the car is almost misfiring.

MAF sensors can cause all 4 if the engine fuel loaded the cats so bad they are destroyed by the raw fuel going into them... Usually though the lean codes would have set way before the cat codes set...

Third thing is to check the vehicle wiring harness... In the US south especially, they were known for the insulation flaking off the wires causing all kinds of weird abnormal concerns.. but usually more bucking than just check engine lights.

I recommend a shop to properly diagnose to see if the cats are toast are not first however...

Answer 3

this indicate you have a vacuum leak or a false sensors. use a smoke machine to find the vacuum leak. this is the best method to test vacuum leak. after fixing the leak, remove the mass air flow sensor. take a flash and shine it into the sensor wire. if you see a lint or fur hair,it is bad. replace it. make sure your air filter seal tight or else it will damage the sensor.

Answer 4

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

Answer 5

You need to replace the catalytic converter... I had the same codes on my Durango.... trust me, it is the converter..... I just changed mine and it is fine now....