What are the symptoms of a bad O2 sensor?
Does it mimic a bad vacuum line,, or a sticking egr valve?

 

There are numerous symptoms; rough idle, pinging, missing, increased emissions, and bad or worse gas mileage come to mind. You most likely will be getting an SES light, so pull those codes and check them.

 

Thanks for replying !!! I have a rough idle that comes and goes..

No pinging
No missing
Good gas mileage
No SES light

Do you think the occasional rough idle I get could be vaccuum ? I have a few of the original hard plastic vac lines that run from the egr selenoid to the egr valve..

Thanks
Melissa

 

Probably not related to egr vacuum, i have had one of those plastic lines disconnected before with no ill effects.

 

o.k. thanks.. Any suggestions?? Happens sometimes when I come to a stop,, if I put it in Neutral it goes away and runs smooth...All tune up parts are good and new fuel filter...

 

When you put mostly any FI car in neutral the idle goes up by about 50-100 rpms. It is programmed into the chip. Sounds like you have a vacuum leak somewhere. A bad o2 sensor would give you poor mileage.

 

Birdman,, thanks for your help !!!!! I finally found it!! SES came on and gave me a code 15... Pulled the 02 sensor and couldn't believe it was the original one from GM...Replaced it with little problem and my car runs much, much better...It took a long time for it to set a code.... I'll keep the original sensor in a box with the original radio I took out !!! My car has 102,000 miles but rebuilt the engine 11,000 miles ago,,,should have changed that sensor anyway........Thanks again for your help !!!!!!!! I will post pics of my car as soon as I figure out how to do it....... It's a beautiful car,,, burgundy w/gold pkg......All stock... Has an appraisal...... Have a great day !!!!!

Melissa

 

Hey guys reading this thread with interest. Have an 87 with 5.7 TPI and experiencing similar issue. No MIL light. I also have an occaisonal slight hesitation in throttle response from standstill. Car is pretty much stock and I know it needs a new FF but have had zero luck freeing the fittings on the old one. Fittings rusty lines not, go figure.... My guess was a vac leak but when one came off (purely by accident) light pretty much came on almost immediately. The rough idle is annoying!