Quick O2 sensor question

[garylau]

Could a very badly leaking exhaust manifold (nickel-sized hole in the manifold and a bad connection to the downpipe) give false readings to the O2 sensor and make the car run poorly?

[mechanicaldj]

question: does it run poorly when the engine is cold?

if yes: then no to your question

the O2 sensor has to fully warm up first in order for it to work

[NovaSS]

Hole in the manifold ? Does it have hair line cracks all around it like a spider web?

I have only seen a couple manifolds burned out, mostly big stuff thats under load all the time. If you burned up a manifold you have problems, more then just an O2 sensor.

[j-stauf7]

Yes, that would be a concern to me.

[garylau]

Okay, well it won't idle at any operating temperature, so I guess it wouldn't be that. Sorry, I can fix almost anything once I know what's wrong, but my knowledge of diagnostics is severely lacking.