I posted on CF but I know the core of the tech crew is here now.

Let me know what you think...

P0174 - Fuel Trim Bank Two - lean
P0171 - Fuel Trim Bank One - lean
P1416 - Air system Fault Bank 2 - port air circuit malfunciton
P0507 - IAC Circuit Condition or Idle speed high/low - high idle

I think the cats might be clogged causing some of this.

I wouldn't be so quick to blame anything. I will check my Helm manual later tonite.

Talk to me:

Mileage?
Maintenance history?
Stock engine?
If no, mods?
And where are you?

Stock to the mufflers. 88k miles. I haven't had the car a year yet but I got a huge folder of documentation. The guy I bought it from is a hard core enthusiast and owns 2 GS's

Try blocking off the AIR system so it cant pump into the exhaust, that could be the reason for the lean codes.

Do you think it really is lean or does it feel ok?

I need to put my hands on my 96 manual... then I can research.

In regard to a couple of questions...

I live in Atlanta GA (unfortunately)

Yes the car feels weak on the top end compared to what it used to. I was also told a bad o2 sensor could cause some of these lean problems.

If you are who I think you are, I remember you from CF! Welcome aboard!

A bad O2 would give a code, too. So don't get into throwing parts at it.

I have found book 1... I need book 2.

Yup thats me Been trolling the Corvette boards almost 9 years now

cool!

I will find it tomorrow... sorry for the delay.

No a bad O2 wont always set a code, if its only fouled, it can still lean things out or fatten them up, however there are 2 DTCs above stating lean mix.

The reason i ask about the AIR system is cause you have a DTC listed for that too, and if that is allowing oxygen into the exhaust stream, youll go rich, while the O2s report lean.

The air system is supposed to operate when the engine is cold and the computer is in closed loop.

this means that the O2s are dead and the computers tables are running the engine.

if the blower is pushing fresh air in all the time, then it's creating a false lean condition.

There is a DTC there to say the AIR isnt working as it should. When it is "supposed" to operate is beside the point, cause its not working properly.

The engine will be in open loop when its cold, not closed, the O2s are in full use during closed loop.

There is nothing to stop the AIR system ALLOWING oxygen into the exhaust flow at any time if its malfunctioned. The electric motor doesnt have to push it in there, itll be drawn in by the exhaust flow.

At which time the O2s WILL be in use by the PCM, and it WILL make the engine run rich.

I get the loops backwards... damnit.

Agreed, the air pump could be malfunctioning by running all the time, too.

Either way, the problem seems to be associated with the air system. I would start with checking the various check valves and make sure they haven't weakened to the point where they are collapsing from the exhaust vacuum.

Ok this is funny. The light went out today while driving.

I replaced one of the check valves a month or so ago. I bought it a Napa and the non-threaded sided was actually a lot smaller than the GM piece...I had to use a large zip tie to get the line to tighten around it enough to stay on vs the plastic piece GM used. Perhaps I should go to the dealer and go for 2 new GM check valves and replace them both?

Look in my sig, find the phone number and order them off MAXX WRENCH.