I have just spent a few hours researching my p0171/p0174 cel codes and now wonder if my broken egr tube coming of the left exhaust manifold is the cause. I plugged the manifold portion to solve the exhaust leak but the upper part is just hanging there. Could the egr tube sucking in fresh air instead of exhaust cause the lean codes? I'm not getting any egr related codes just the 171/174. The codes did not come up until about 200mi later. Truck is a 1997 F150 4.6. Thanks in advance for any help.

 

Yes. That is most likely the reason. Though the only other thing I could think.. well the only logical would be a dirty MAF. You can try to clean it but I know that it would normally mean the EGR is leaking exhaust into the manifold because it's not closing all the way. I imagine if the tube is left open air would leak in... Ultimately I would suggest replacing the tube. Your fuel economy will suffer w/o the EGR functioning correctly.

 

Thanks for the reply. I'm going to do a MAF cleaning this weekend and see if I can splice the tube together instead. To put a new tube in will require a new exhaust manifold because where the tube threads in is a rusted mess. I was hoping to hold off on that project until spring