FAST O2 Not Correcting?

[Blown98RT]

I have a SpeedPro with wideband and I am not getting any O2 correction. My actual a/f is much leaner than my target a/f. It is set to 25% correction accross the board, the wideband is recognized by the ECU. I have Closed loop enabled checked, max rpm at 1500 and low rpm at 1200. The connections are good. Any ideas? The gain is set at 30%. Should I raise this number?

Thanks,

 

[bobc455]

I assume you're also above the temperature where the O2 sensor will be activated, and waited until after the time for the closed loop to kick in (delay)?

Are you seeing 0% O2 correction on the dashboard, or are you just assuming it's not working because you're still lean?

-Bob C.

 

[Blown98RT]

Hey Bob, I am past the delay time and over the temperature in which the wideband will kick in. It is showing 0% O2 correction on the dahsboard and log. I'm not sure...

Thanks,

 

[Craig Smith]

Does the sensor seem to be displaying a/f ratios correctly? If the sensor is reading a/f ratios then everything is OK and something in your setup is causing it not to go into closed loop. Check the correction limits and make sure they aren't at zero. It is not possible for the O2 sensor to be working properly but the ECU won't go into closed loop, so if you feel confident that the sensor is reading OK, we can rule that out and take it from there.

Craig

 

[Blown98RT]

Craig, the wideband appears to measure the a/f correctly. The numbers look corect. I have correct limit at 25% for adding fuel and 10% for cutting fuel. Thanks for the help!

 

[Craig Smith]

The info in the closed loop parameters should be pretty self explanatory, so if you have all that set, there's one other "lesser known" culprit - after-start fueling. If ANY after start fuel is being applied, the ECU will not go into closed loop. Double check your after start fuel settings and make sure that they aren't somehow set to have the after start fuel lingering for a long period of time. You'll see a sensor in the dashes on the after start screens called "Aft. Corr." and this will show how much, if any, after start fuel is being applied. See if this gets you anywhere... good luck.

Craig

 

[Blown98RT]

Craig, I think that might do it. I have never looked at that sensor since I don't have it on the main dashboard. The only culprit I see is the After Start vs. Coolant Temperature which is set a .4% enrichment from 173 deg. on. Unfortunatelly it is raining here...I will try that as soon as the weather breaks. Like you said, everything else if is self explanatory. If that doesn't do it...i'm really stumped.

Thanks,

 

[Craig Smith]

Even if you have the after start set at .4% it should go away after a few seconds. There are two other screens relating to after start fueling - one sets the number of revolutions after going into run mode before the fuel is applied, and the other sets the rate at which the fuel is decayed out. I've seen this get set so that the fuel lingers in some small amount for a very long time and that's all it takes. You can use the settings in the demo calibration file on your C-Com disk as a good comparison for how the graphs should look. As long as your settings are at least similar, that should be OK.

Craig

 

[Blown98RT]

Craig, I have all 3 after start graphs identical to the Demo.cts that ships with the software. Still no O2 correction. The only correction I see is 0.8% for Batt Corr. Could this have any effect?

Thanks

 

[Craig Smith]

Hmm... this is strange. Like I mentioned before, if the WBO2 is working and displaying a/f ratios, it isn't possible for the ECU to be unable to go into closed loop. It has to be a setting in the tuneup file somewhere. Do this for me if you would: Go online, look at the closed loop parameters screen and reply with all the info on the screen. Also, while you are online, verify that the correction limits are set to something other than zero for every row of the graph. The last thing to check is that the UEGOS voltage stabilizes at .45 volts or so while the car is running. This will take about 30-45 seconds to stabilize from a cold start, but that's where it needs to be. This voltage tells a lot about the condition and the functionality of the sensor. Let me know when you have a chance and I'll do what I can for you.

Craig

 

[Lance]

The only other thing the ECU cares about before allowing closed loop is the UEGOS sensor value. It needs to be around .45 volts during operation. If above or below this value, the ECU will not allow closed loop operation.

Also make sure the O2 heater is operating. You should simply be able to turn the ignition on and feel the outside of the sensor warm up over a couple minutes.

One other thing to check (depending on the model of ECU) is that the N2O enable input is not connected to 12V. You can check the"N2O Enable" sensor in the main dash and it should be 0. With some models of ECU (Buick V6 SEFI) the N2O enable will inhibit closed loop operation.

Lance

 

[bobc455]

Lance-

Perhaps I don't understand you correctly, but if closed-loop is disabled (inhibited) when the N2O is enabled, how does it control toward the N2O target A/F ratio when you're spraying?

-Bob Cunningham

 

[Lance]

Originally posted by bobc455
Lance-

Perhaps I don't understand you correctly, but if closed-loop is disabled (inhibited) when the N2O is enabled, how does it control toward the N2O target A/F ratio when you're spraying?

-Bob Cunningham

Sorry. I guess I wasn't specific. On systems that don't have nitrous capabilities (Buick SEFI), the N2O enable can be used to inhibit closed loop. This is useful when on the trans-brake and 2-step so the mis-firing does not affect the A/F ratio and cause a false correction from closed loop operation.