P1124 P1126 at idle

[Jrboulder]

I have a new to me 99 C2 with a CEL that keeps coming on. Originally it also included P0130 but I replaced the corresponding O2 sensor and that code hasn't come back.

I can clear it and drive around for a while but if I let it idle for a couple minutes once warm the CEL light will come on.

Typical freeze frame data is coolant 205F, speed 0, rpm 740.

My understanding is that this is too lean for the computer to correct for, on both banks. So probably a vacuum leak along the shared path.

MAF is clean
hoses/connections appear OK
no whistling sounds

I don't have access to a smoke machine and I'm not willing to spray flammable chemicals on a hot engine.

I hate throwing parts at a problem that doesn't have a positive ID but I think I may have reached a diagnostic wall where I can either pay someone to diagnose it or just take it apart along the route of engine-in AOS and see what I find.

Any ideas?

[Jrboulder]

The AOS bellow doesnt look great, I'll change it and see what happens.

[shepmess]

I think you found your problem JrBoulder.

I had the same two codes in my 99 and it was keeping me from passing smog.

I built a smoke machine, looked all over for a leak and replaced a bunch of parts with no luck. Oil cap, gas cap, air flow meter, etc.

The final thing I did was replace the AOS Bellows and that solved the problem.

[Jrboulder]

I got the bellow installed today and it was immediately noticeable how much better the car runs.

Using new spring clamps I couldn't manage to get the bellow onto the AOS. One side would always tuck under.

I ended up installing the bellow with no clamps and then putting some 20-32mm screw clamps on. Much easier.

[edwardraab1]

I had the same issue. I changed the AOS and cel again came on after few miles, while sitting in traffic. I then changed the MAF and has not come on since. I recommend buying the Bosch MAF for $250 instead of $500 from dealer, since the same item.