Starting noises 2001 3.4

[neuro_optic]

My 01 GA with the 3.4 is acting up again!! When I start it when its warm, sometimes it has to crank quite a bit before it starts and it stalls out sometimes after it starts. It has like 59,000 on it and I am changing the O2 sensor this week, becuase I am getting like 10-15 MPG and was told it is the O2 sensor, could the O2 sensor cause hard starts? Also when it does start when warm, sometimes it make a knock noise at startup, no not like a bad engine or bearings and it only does it once AT start-up. It is almost like noise that might be associated pre-detonation or a timing noise. It only makes that one knock noise at start-up when warm. No matter how much I rev the engine or drive it is a quiet as mouse the rest of the time.

JCM

[rixGAphx]

Everything you describe seems exactly right for a bad O2 sensor at the engine (not the one at the cat).

Change it and report back if anything is still wrong.

-Rick

[grandam01]

ok i have the same start up problem every now and then also it has become more frequent but i get loud blow-off valve sound, ya know, like the engine is pushing air out, but it comes from the intake. WTF this is getting annoying cause i don't have a turbo.