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Discussion Starter #1
If I unplug my upstream O2 sensor, will that force a "rich" condition? In other words, will it force a rich commanded AFR? It should change if this is not my current issue for my rich commanded AFR, right????
 

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What is your O2 sensor reading? I know it is probably in the other thread, but since you started a new one it is easier to ask. I think that if you unplug it you will immediately get a code and will probably go into some sort of limp mode.
 

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Discussion Starter #3
I know... it actually stayed at 13.79 for my commanded AFR...so I'm wondering if its not the upstream O2 sensor, or something in the emissions.... It reads between 2 (super lean or 27.58) and .78 which is pig rich....
 

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It appears to me that the sensor is working. I wonder if you don't have a bad injector. What does the injector control look like?
 

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Discussion Starter #5
The pulse length seems to be pretty consistent across all 4 of them. I do have occasional misfires on 1, 2 and 4, but it only seems to happen during FCO and I think that's because it's commanding 27.58 instead of 29.4, so it's getting just a tad bit of fuel in there. I ordered an hptuners cable so I can data log with it.... I was hoping someone near me would step up, but the 2 members that are close to me and have hptuners won't do a log to help me. I got someone to finally say yes, but they live about 45 minutes from me. I'd just rather order the cable so I can do it when I need to now...
 

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Are you saying that the injector pulse doesn't react to the O2 sensor reading? That sounds like you are in open loop control. Some form of limp mode.
 

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Discussion Starter #7
No..the O2 sensor does react, but the commanded AFR seems to react more to the gas pedal position then the actual measured AFR reading. Torque shows the car goes into closed loop, but not sure how it determines that. If it does it by temp sensor on cat, then there could be an issue of the car staying in an open loop and me not knowing it. My problem is that the tuner at ZZP could have turned the CEL light off for certain things and I don't know it. I'm also wondering if my waste gate isn't stuck open....I hear a lot of air rushing that I've never heard before when I go into boost.... But the car still goes. Just yesterday I was driving it. Layed rubber all through first and second gear at 21psi....just sounds different now though with all the air rush sound.
 

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Discussion Starter #9
So John...I think I FINALLY have the answer. Apparently the tuner that did my tune shut off the O2 sensor CEL. I just went down to put gas in my car (about 3 miles each way) as I was going to drive it tomorrow to work (about 14 miles each way). And my Torque app FINALLY showed this message on one of the gauges:

Fuel Status: Closed Loop 1 O2 sensor (fault)

So I'm going to guess that this means sensor 1, the upstream O2 sensor (wideband)?

Too be honest, the vibration is gone...so I'm "hoping" this is the issue!!!! :yay:

Of course I've been known to be wrong before!! LOL....
 

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So John...I think I FINALLY have the answer. Apparently the tuner that did my tune shut off the O2 sensor CEL. I just went down to put gas in my car (about 3 miles each way) as I was going to drive it tomorrow to work (about 14 miles each way). And my Torque app FINALLY showed this message on one of the gauges:

Fuel Status: Closed Loop 1 O2 sensor (fault)

So I'm going to guess that this means sensor 1, the upstream O2 sensor (wideband)?

Too be honest, the vibration is gone...so I'm "hoping" this is the issue!!!! :yay:

Of course I've been known to be wrong before!! LOL....
Really? Disabling the #2 O2 sensor MIL is pretty common, but I have not heard of disabling it for the #1.

Yes, O2 1 would be the upstream wideband sensor.

So, the vibration is gone, did you replace the sensor?
 

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Discussion Starter #11
Hey John...I did not replace anything. I tightened down all of my ic piping clamps, from the turbo the throttle body elbow. I drove the car to work today. Got the same error and then about 5 miles from work, it cleared itself and showed open and closed loop after that. Vibration was awful this morning.

Got in the car at lunch....not vibration..none...nada....zip. Drove the car home, no vibration, but it's still commanding very rich. I was looking at my torque logs and the downstream o2 sensor is REALLY lazy...like 10 seconds lazy to go back to rich. I'm going to just replace both and hope this cures my issues. I was reading that the downstream should hover around 0.47...and mine is either 0.9 or 0.1...with a +- of .1. It's never hovering around 0.47. Ordering them as we speak from Amazon.
 

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As far as i know, the downstream sensor has no effect on the engine, it is only there to monitor the cat.
 

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Discussion Starter #13
According to a tuner ive been talking with on the Cobalt forum, it does control emissions and AFR to an extent. And if its lazy, the computer automatically goes into an enrich mode to not damage the cat from running too lean but wont set a CEL as long as its active. He said it will only set a CEL if it loses connection with the ECM. Now how true that is...I dont know. I haven't been able to find anyone to back that up...but hes got a lot of posts over there and seemed knowledgable.
 

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Discussion Starter #14
So a question John...what's the highest and lowest value that a wideband O2 sensor should see? I've read 0-5 volts... but mine is only showing 0-2 volts. Any thoughts? My new sensors should be here tomorrow...but just wanted to know.
 

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Discussion Starter #16
Thanks for posting this thread Ghost as its a real learning curve for me.
NP

So I was going back through some of my previous logs from when I was having my HPFP issues and before I had my exhaust replaced. I did do research on my evap system and my evap system is within parameters of kPa.... Furthermore, my commanded AFR now and commanded AFR then, have the same ratio...so by deduction, I believe my wideband O2 is good. However, the one thing that I did find was that all of the logs prior to having my exhaust done, do not have any feed coming from the downstream O2 sensor.... Now it does. So...that leads me to believe that the PO didn't have the downstream O2 sensor plugged in. And when my dyno tune was done, I would also be led to believe that the turner shut off the MIL for this sensor because it wasn't showing in the tune. So I'm going to disconnect it again and see if this fixes my rich issue. Now, if the tuner I've been working with on the Cobalt is correct, and this sensor was not used to tune initially, my car should got back to a commanded afr of 14.7..... So I'm going to work on this and let you all know....BTW, is the plug the one on the fire wall up under the cowl for the downstream O2 sensor????
 

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A slightly rich condition wouldn't cause your car to vibrate period. Check your motor mounts and trans mounts. Why are you logging AFR? Log lambda the car would try to be at lambda 1 regardless of the ethanol content in the fuel or type of fuel. Remember if the car is running extremely rich condition it would set a code!

Check the upstream 02 sensor, injectors, hpfp and the tune!

The bank 1 sensor 2 o2 sensor in the kappa platform does not affect fuel mixture, is not like a BMW that uses both sensors to regulate fuel mixture.
 

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Discussion Starter #18 (Edited)
But at 1k rpm its not a slight rich condition. AFR at 1 k is 11.2 or less. Furthermore, I do have it logged at lambda and it is commanding 1. We dont have anymore ethanol in our gas then we had 4 years ago...so why is the commanded AFR suddenly 13.7?

You're talking to a guy that knows when his car reaches 220 degrees without looking at the gauge because the sound of the engine changes. My car doesnt sound the same at cold start. Instead of idling at 1500 when cold, it idles at 1k. While it's still a rocket...theres a lot more rushing air sound when I get my 23psi of boost. All of this tells me something has changed. And the only thing logical right now is the commanded AFR. Furthermore, I believe the cat is hotter then normal as I'm getting fogging on the passenger window and passenger side windshield when I drive the car in the morning to work...I've NEVER had this!

The HPFP was replaced 2 years ago and has less then 5k on it. The tune just cant change on its own and hasn't been touched in 4 years. And from what I can tell the upstream is working properly. By saying the upstream is working properly, when I do the math and look at it...1.05v is 14.43afr when commanded is 13.79. When commanded was 14.7, 1.05v was 15.46. So again...something isnt right...and a tune cant just change itself...and these are perfectly in line with their respective numbers.

14.43/1.05=13.74.
15.46/1.05=14.72
 

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............theres a lot more rushing air sound when I get my 23psi of boost. All of this tells me something has changed. And the only thing logical right now is the commanded AFR........
Nothing about the AFR is going to make a "rushing air sound". You must have a leak somewhere.
 

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Discussion Starter #20
But wouldnt that throw a CEL? I'm still getting 23psi of boost.
 
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