I finally hooked my computer up to WinALDL and got everything working right. I started pulling data off it and I've noticed that the O2 sensor readings are all whacky. Nothing stays relatively stable even at idle. Would this indicate that the O2 sensor is on it's way out? Im positive its the original one from 16 years ago as the car only has (now) 54500mi and 48150mi when I purchased it.

And how difficult will it be to remove the old sensor if its time to replace it?

 

I just found the O2 readings that I had written down.

At idle it would go anywhere from 230mv up to 840mv
At about 2000rpm(about 100kph) it would average 550mv-980mv with the occasional drop to 30mv-50mv (not forgetting the 0 either)

I did this with WinALDL connected to my car with my friend monitoring it as we drove.

 

The readings sound OK, as far as all that goes. At idle for instance, the ECM is constanly trying to vary the idle mixture from lean toi rich and back, several times a second, and will light the "Check Engine" light if ic can't make it happen. The name for that is "cross counts".

Problem is, if the O2 sensor is bad, it's entirely possible for the ECM to do stuff to make the readings look right to it, even though the bad readings don't correspond to reality.

Aside from the usual problems of getting at it and dealing with it being stuck from age, it's pretty easy to swap. They even make a special socket for it, that has a slot for the wire to go through.

 

Im still new to how to interpret the sensor data on this WinALDL program.

What would be normal symptoms of a poor or failing O2 sensor?

Right now the car runs fine over 600rpm without any problems whatsoever. If it dips down to where it likes to idle (475-500rpm) it makes the car shake(which feels normal) but every few seconds it will sound like too much gas has gotten into a cylinder causing it to fire stronger than normal sorta like a crappy snow blower when it stutters(but definately not as loud). The rpms usually fluctuate when this happens.

I also noticed that when monitoring the flag data in WinALDL the "rich" flag toggles on and off repeatedly.

I've already dumped 2 bottles of STP concentrated injector cleaner(the symptoms were more noticable before the injector cleaner, hard starts, rough idle, etc) into the system at fill up, fuel filter was replaced by GM, the plugs, wires, rotor cap and rotor were replaced by GM, coolant flush and synthetic oil change was also done by GM. I was curious to know the life of an O2 sensor as that would be the next thing to change up in it's overhaul.

The previous owner did nothing but change the oil and flush the coolant before storing it for the winter so im wondering if I should continue looking at the O2 sensor or start goin somewhere else for this minor driveability issue.

Much appreciated the response though!

 

The O2 sensor should be replaced as part of every tune-up, or so they say. And we all know about what "they" say.

Replace it and see if the car runs any better or uses any less gas. It usually has both of those effects.