system running to lean bank 1 code P0171

i have a 1997 ford windstar xl and it keeps sending code P0171 system running to lean bank 1. i have replaced the fuel injectors and spark plugs and wires. what else could cause it to run to lean?

thank you

Kevin

i have a 1997 ford windstar xl and it keeps sending code P0171 system running to lean bank 1. i have replaced the fuel injectors and spark plugs and wires. what else could cause it to run to lean?

thank you

Kevin


Un metered air entering the intake. Since you are only getting one of the codes (left or right but not both) it would seem to be a leak to an area that is specific to that bank.

Someone correct me if I am wrong but I think that the code means that the O2 sensor is detecting the exhaust too rich. The PCM should try to make the fuel-air mixture leaner in response to this. But, if after reaching a certain point the mixture is still too rich, the PCM will throw the code. It is basically saying that it has made the mixture as lean as it can and it still is not enough.

I got this same code (P0171) when I had a blown lower intake gasket which allowed coolant into the fuel-air mixture. This apparently prevented good combustion and the O2 sensor would detect the extra fuel in the exhaust. After 6 months, it got bad enough to where I had a white cloud of steam pouring out of the tailpipe.

Another hint of a blown intake gasket, the rubber vacuum lline with the 90 degree elbow that plugs into the top of the upper intake will degrade over time. It may be loose and even wet with coolant.