My 97Z is giving me the following codes:

P0171
P0174

After I searched I found out that these are for left and right bank lean codes. I read elsewhere searching that its also most likely a vacuum leak. I have the EGR deleted (physically and codes both gone) but the AIR pump is still in the car. I dont think that has anything to do with it just thought Id mention it. I have replaced the fuel filter recently but had the code before that. The codes first showed up after I had a computer tune done, I had the egr deleted before I physically removed it. I have now removed it, block off plates and all and cleared the codes and they came back.

Just wondering where in the process I should start to figure this out. I havent had the intake elbow off so I know its not that, I check it also. Ive been told it could be an exhaust leak or o2's, not sure though. I dont have any scan tool type software either, just going off of a cheap code pulling device for now.

Any suggestions or common things that may be causing this?

Thanks

 

The codes set because the long term fuel corrections on both the left and right banks of the engine are approaching their maximum value of 160, adding up to 25% extra fuel, and the O2's are still reporting a lean condition. The fact that it is happening on both sides of the engine would appear to indicate its not something like an exhaust leak before the O2 sensor or misfires, unless both banks just happened to have the same thing happen at the same time.

Lean conditions can be caused by low fuel pressure, incorrect MAF readings, large vacuum leaks, or faulty O2 sensors (false lean). Again, for it to be the O2 sensors, the sensor (or wiring) on both sides would have to go bad at the same time.

Have you checked your fuel pressure?

While you feel your inlet elbow can't be damaged because you haven't removed it, check it anyway. Its there to absorb movement as the engine moves around under load... it could be torn.

Check the blanking plate for the EGR valve.

You show "!AIR" but you indicate you still have the AIR pump. What did you actually delete? Did you delete the manifold connections and plug them correctly? Did you delete any of the AIR system vacuum connections, and plug them?

Check the vacuum connection cap for the deleted EGR.

See if the MAF sensor is dirty.

Check the vacuum lines for the EVAP system.

Check the large vacuum hose for the brake booster. Has braking pressure increased at all?

 

Ill start there and report back, thanks