what are the symptoms?

i think i might have to replace them.

I have a 94 Z with 91k miles... original 02 sensors...

Mac Headers, no cats...

 

Crappy idle and elevated gas consumption would be two clues that the O2's are bad. Might even throw a SES or code.

 

When the ECM/PCM isn't getting the 1 MV from the sensor it throws a SES code. Might want to change them anyway, It's only about $50 and an hour of work, and will probably improve your fuel economy... even though they may or may not be bad, they're still pretty nasty by now.

 

ok this is my problem....


Car runs fine at WOT but when i am cruising at around 45-55 mph in 4th and i step on the gas lightly the car bogs a little when it is anywhere from 1500rpms to 2300rpms kinda... after that it goes. If i press it more than necesary it will downshift and won't give me that problem...

any ideas?

Spark plugs, wires and optispark are farily new.

 

Jon just get new O2s already. I got mine (genuine AC/Delco parts) from Rockauto.com for like $63 shipped. Its worth it to know if that fixes your problem or not.

 

The EGR functions at high load low to med rpms. Those are the conditions that you describe. Might be bad.

 

I have the EXACT same problem as you. Down to the gear and the RPM and milage. My problem stated to get worse, and I then changed plugs and wires, all other stumbles went away except for that one.

BUT, starting today, its getting a stumble under load for a few secs then goes away. I'm thinking its the opti, but i'm goan replace the fuel filter first and hope for the best.

I already have money on side for opti, but I dotn want to spend it jsut yet.

 

Bad O2's can cause a lot of problems that were already mentioned, I would think there is a good chance they could be bad if they have been in for 90k miles. I beleive manufacturers recommend changing them at least every 50k miles. Thats when I changed mine.

 

when my passenger side O2 went bad, my car would throw a ses and then would go away after a view seconds. Think that made me think it was 02 b/c when I revved it up, black smoke poured out the exhuast. If it wasn' stumbling or almost stalling, it would at least feel slow at WOT.

 

$63 shipped on two o2's is one heck of a deal.

 

I just changed my 90k miles old O2s. I was not having any problems, but hope to see any improvement in gas mileage.

 

How about this? Start with the cheapest (EGR), and then work your way up, O2's, etc... I would replace the plugs wires and opti LAST!! If you do a search on these problems, very rarely does it turn out to be the opti, and there are a ton of people that have spent a lot of money for nothing. I just want to save you a few buck

Also, check the vacuum lines, there could be a crack or leak in one