93 corvette--poor idle/running rich/surging/bucking running out of ideas

[HellaciousA]

@GaryDoug

I opened my copy of the 1993 version of TTS Datamaster. In the "setup" screen there are options for:

- Y-Body Manual Trans

- Y-Body Auto Trans

- F-Body Manual Trans

- F-Body Auto Trans

If it works, I think it would be worthwhile for him to download your 1993 Datamaster File. That way when we can look at data we can have more confidence in.

What do you think of the fact that after the O2 sensors were switched side-to-side, the problem stayed on the driver's side? With a single wire O2 sensor, and the problem not being the sensor, what in the circuit would cause the voltage to hang at what may be the upper limit (1,132 mV) for 15 minutes of idle, then when the car was driven, slowly drift down to 350 mV and stay there?


@HellaciousA

When you say the problem remained on the driver's side, did you scan it and if so, did your driver's side O2 voltage show the same pattern described immediately above?

I didn't rescan--I just was able to see the cat glowing again and hear the exhaust popping, and the strong fuel smell. Given how inaccurate the data was with 9495scan, I didn't think there was a point. I used to have a copy of datamaster years ago, but I don't. If you guys have the setup file, I'd be happy to run that and do another data log.

[GaryDoug]

If it works, I think it would be worthwhile for him to download your 1993 Datamaster File.

I don't have the 93 version file, only the 94/95.

What do you think of the fact that after the O2 sensors were switched side-to-side, the problem stayed on the driver's side? With a single wire O2 sensor, and the problem not being the sensor, what in the circuit would cause the voltage to hang at what may be the upper limit (1,132 mV) for 15 minutes of idle, then when the car was driven, slowly drift down to 350 mV and stay there?

There might be a bad ground wire in the cable or the pcm could be defective. I would check it with no sensor plugged in to see what voltage is present and I would use a multimeter just in case the program has a defect.

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[HellaciousA]

.....

I followed page 6E3-A-81 of the service manual, and it was still showing about 1.1-1.2 volts bank 1 o2 sensor voltage with temps around 160-180 degrees. I disconnected the sensor and put my DMM in the connector and grounded it, and voltage showed .5 to .7 volts. On scan9495, the data wasn't clear, but on the chart for that bank, it was almost always at or near 1 volt, with bank 2 showing a more normal range. Per the service manual, it states to replace the ecm if the voltage doesn't go below .35 volts.

I fully expected to see an SES light show up, but none appeared. But I did get "Service ASR" and "Service Ride Control". Sounds like it's time to get a new ecm and hopefully once and for all this sorts it out.

[AL 9C1]

That's always the big money gamble right there. Pointing to ecm but it always sucks because of the doubt. We've replaced computers and fixed issues and have also replaced them and it was something else. I hope the ecm gets it done. I'm pretty curious to hear the outcome.

[HellaciousA]

Just to rule out any other wiring issues I hadn't already checked, I checked continuity on the o2 sensor harness from the body to the ecm and it's good. Knock sensors are also good and no damage found to any connectors or wiring I can see in the engine bay.