Finally got Datamaster to work (all be it intermittently) so I hooked it up to the vette and sat idling for about 20 minutes.
What I found, and what I need advice on is:

I'm pretty sure, but just to confirm, there are '2' (two) O2 sensors on a '93 vette right?.

The left O2 was giving a reading around 870-890 Mv, but on the right O2 I was getting a reading of 4 Mv's, and a code 64, the car also was constantly in 'open loop' (I have heard idling can force open loop so that maybe irrelevant). Is this likely to be a bad O2 or a wiring problem?.

The injector pulse width and duty cycles were around the same for both sides.

Also, anyone know the part # for the O2 sensor and whether an 'F-body' (firebird/camaro) sensor would work?.

Any help would be appreciated.

Thanks
Sara Lou

 

The ECM adjusts the mixture continuously from rich to lean and back to rich, etc. The ECM looks at the O2 sensors to determine when to switch. You should see the O2 sensor voltage moving constantly between approximately 200 mV and 800 mV. If it stays at one extreme then you have a problem with the sensor, wiring or inside the ECM.

Each time the O2 sensor crosses the ideal mixture point (450 mV) the ECM adds to a variable called "O2 cross counts" (or something similar - the exact name depends on your software). The cross counts go up to 255 and then roll over to 0. The counts should change approximately once per second. If they are not changing then you probably have a problem with the O2 sensor.

 

Stay with OEM sensors.

 

I just got a new O2 sensor from Rock Auto. Good price and quick delivery.

 

Or, maybe with the datalogging. Sounds like neither side was oscillating as expected.

 

I looked again at the datalog today (but ran it frame by frame this time), the left O2 seems to work fairly good, low 190's high 800's, fluctuating rapidly between the highs and lows, BUT, only when the car is in closed loop?. Once it knocks back into open loop the left O2 stays up around the high 800's.
The right O2 pretty much stays around the 4 to 13 mark regardless of open or closed loop.

I'm pretty sure the logging software is a contributory factor in this, but from what little data I can get, it seems constant to what i'm seeing with the left O2 working in closed loop and the right O2, for all intent and purposes, is dead.

One reason I ask about "F-body" sensors working, I have a pair of 4 wire heated O2's off my '94 firebird I thought about trying in there to see if the sensor was bad or if it was further 'upstream'. I don't yet know what i'm dealing with till I can get the car up in the air and look.
I do know it has hooker long tubes, and judging from the mess of varying bolt lengths, 2-3 gaskets where they bolt to the heads, and half the accessory bracket bolts missing/loose, who knows how the O2 sensor wires were extended!. This hasn't been the best cared for vette over the years of prior ownership.

Sara Lou

 

Sounds safe to assume your ECM isn't getting a signal from your right O2 sensor. If easy enough to do, I'd consider swapping them to confirm if it's the sensor or wiring above it.

During warm-up, O2 sensor readings aren't reliable until they get hot. Once in closed loop, they are. When you hit WOT, O2 sensor data is ignored. IDK, maybe the ECM doesn't even capture O2 data during WOT.

 

Any ideas why the car would throw itself into 'open loop' after a few minutes of idling in 'closed loop'?.
I really need to take it out for a run, but until I can get this logging problem fixed, there's not much point.

Sara Lou