p171 lean code -My Unusual Problem & Solution

[baron1701]

Hello,
I have been chasing down a P171 lean code for many months. I have gone down the list of things to change and replaced nearly every sensor, gasket, seal, vacuum line, Oxygen sensor, MAF sensor, valve cover gasket, fuel injector seal, fuel clean, fuel pressure test,ect. that I could think of.

Today I went overboard with my third can of fuel injector cleaner and found that the idle changed most while near the throttle body but closer to the EGR Valve. I removed the throttle body and somehow the EGR Tube connecting the EGR mount thingy and the lower intake plenum had developed a severe crack. Went to the junkyard (Pre-owned vehicle component storage facility, for what they can charge sometimes) and pulled a much better looking tube out. I still need to wait for more driving data but I think this was clearly a, if not the problem. I think that if this keeps the SES light off then I will buy a new tube ( $20 ) and enjoy some trouble free driving.

[maxwedge]

Hope that does it, as a bonus you just saw the benefit of proper diagnosis vs random parts replacement.

[baron1701]

The car runs much better but I still got an SES light this morning. I did notice an exhaust leak at the flange for the Catalytic Converter. I may be in trouble because it seems like it isnt the gasket but the converter itself before the flange. The covertor performs fine, if it is leaking and I pull it down do you think any shop will do a quick weld or will no one touch it?

There was also some leak where the converter slips into the long exhaust pipe at the rear. Is there some gasket that should be there? It seems like it is just meant to be held in by pressure alone.

[maxwedge]

Usually the rear of the cat is welded to the pipe, the front you could do the same if it is not rusted, a universal cat installed is about 150. If that code is back keep looking for vacuum leaks, doesn't take much to go outside fuel trims.