My 87 IROC 350 was put on my friends scanner today to try and figure out why I have a slight stumble off idle. Well it isnt switching between Lean/Rich. I havnt checked what kind of vacuum it is making but where should I start? I am going to go ahead and do the o2 sensor because I'm pretty sure it has never been changed.

 

LBC,

How many miles are on the O² sensor?

 

Probably 106,000miles.

 

I'd say you got your money's worth from that one. You'll probably save the price of the new sensor in the first five tankfuls of gas, anyway.