Strange STFT spikes

Update: Took another drive. At the end, the Actron now reports EVAP is complete. Mystery of why the K7 and Actron were not reporting the same I/M status is still active.

Don't really want to clear codes and start over to try to figure it out again.

I'm still thinking the STFT are wack. My typical test on that car, and in fact any car, is to look at the fuel trims at idle and at normal driving throttle to see if they are with +-10%. If they are not, I'm looking for an issue causing it. After I cleaned the map and replaced the purge valve, both fuel trims were in range on the live data graphs in Torque. I guess I can go run live with Torque and see if the spikes don't show up in the live chart....

fj5gtx wrote:

The Actron scanner I have says the EVAP I/M is still inc. But the K7 shows everything "OK" in mode #06... not sure what to believe.  
 

Yeah, that's (unfortunately) typical of all Launch based scanners. They're not actually OK, they just show OK by default until the test fails. You have to go into each test and see if the results are actually populated, or if they're all zeros.

This is a shot from a TopDon (also Launch based) of an incomplete EVAP monitor. All the results are zeros, which means nothing is actually OK and the monitor hasn't run to completion yet.

 

I'm still thinking the STFT are wack. My typical test on that car, and in fact any car, is to look at the fuel trims at idle and at normal driving throttle to see if they are with +-10%. If they are not, I'm looking for an issue causing it.

You're not wrong to pursue total fuel trims over 10%. But I still think normal operation of your Cruze is to throw up short term spikes.

I wanted a better example, so I dug around and found old capture I took from a 2011 Cruze 1.4L. No issues, known good. The short term trims spike at around frame 1,200:

www.scanshare.io/share/RXejd8wF_kqiqg4thzzwzA#0,11,22,26

 

The spike occurs during a transition from fuel cut decel, back to Closed loop. Here's another capture from the Exhaust Aftertreatment data list that shows the same thing:

www.scanshare.io/share/ZPsPK1HS2Eedv27Q3wgLWg#7,11,19,25

 

Good to know that launch reports "OK" until they *know* it is not OK !  

So I think the 6spd manual massively complicates the picture - see charts. 

I have to prove this out, but I'm now assuming the STFT spikes are so transient that when I look at them live in Torque - they get averaged out in the visualization and the STFT appears within +-10%