Strange STFT spikes

2014 Chevrolet Cruze Eco 1.4 Turbo with 6spd Manual.   155k miles

After a P0299 code, checked the infamous boost check valve in the intake manifold to find it gone.  Replaced valve cover and intake manifold.   Car starts and runs pretty good.  Clutch on the AC compressor cycles when at idle and engine rpm bounces.  That could be a separate issue, so ignoring that for now and leaving the AC off. 

No codes.   Keeping the AC off, took a test drive with data logging.   Using a Amazon bluetooth obd2 with the android Torque App to monitor and log.   Looking at fuel trims, I'm seeing a strange STFT spike.   Doesn't seem to change LTFT that I can tell.   

Attached is a chart of my test drive.   What could be causing the STFT to do that?

Thanks!
 

 

Without some more context, there's not much be gathered from fuel trim alone.
At minimum I would want to see loop status, rpm, vehicle speed, throttle angle and o2s, MAF calculated and actual to know when and why the trims go high.
It could be part of the cat monitor, or it could be meaningless if it in open loop fuel control.

Attached is the csv file in a zip format, has everything I can get w/o custom pids. 

I plugged in my actron cp9780a. Went through the State OBD check. All monitors completed, except the EVAP System. I replaced the purge valve last month because it had a pending code.

Thinking it is time to upgrade to a Kingbolen K7, so I get all the functionality in one unit.

Curious too, the Actron is saying I have a bad LR wheel sensor, yet the ABS light is not on. Weird.

fj5gtx, I had a look at your data, but couldn't find loop status in there. Did I miss it?

Wanted to find loop status because that generation of Cruze commonly spiked the short term trim when transitioning from Closed to Open loop, always on fuel cut deceleration. I never got a satisfactory answer on what the strategy is, exactly, but they all do it. Probably even more noticeable on yours as a manual transmission.

Aside from the outliers, your Cruze spends most of its time within 10% of zero, which is excellent. 

Thanks Tyler!
Unfortunately you did not miss it.  For the Torque app and the bluetooth obd2 interface I am using, loop status wasn't in the list of available pids. I would have to add a custom pid to get it.

I wasn't paying too much attention to decel. I was aware the injectors would cut off the fuel in that condition, but it didn't occur to me that it would spike the short term as a side affect.

I received a Kingbolen K7 scanner last night.   I'll set it up and see what if I can capture more data, including loop status.   I'm assuming I can datalog and dump to a file that I can transfer to my laptop, if not I'll be disappointed. 
 

fj5gtx wrote:

Thanks Tyler!
Unfortunately you did not miss it.  For the Torque app and the bluetooth obd2 interface I am using, loop status wasn't in the list of available pids. I would have to add a custom pid to get it.

...

I received a Kingbolen K7 scanner last night.   I'll set it up and see what if I can capture more data, including loop status.   I'm assuming I can datalog and dump to a file that I can transfer to my laptop, if not I'll be disappointed. 
 

Gotcha, no worries.

Let us know how it goes with the Kingbolen. I haven't used the K7, but it looks to be Launch based, which don't include a way to export data files. I'm happy to be wrong. That's one thing that Torque gets right.

Tried out the KingBolen K7 tonight. I didn't see the openloop pid in the list for live data. In fact I didn't see vac/boost either - disappointing. I'll need to dig around a little more to understand if its possible to get more pids than Torque provides. I had hope that I'd get more pids just showing up in the tool without doing anything special.... I'll look a little harder at that later.

The reports are easy to export, but user interface does not support exporting data logs.

So I figured out how to mount the K7 as a usb drive and retrieve the datalog. I found a sample data log I created. However it is binary (with a .TC extension). Seems like TC spells out to Think Car.

Google search found someone who talked about creating a python script to convert it to a csv text file, but they were reverse engineering the TC format for a transmission module.

One could likely create a generalized TC file to CSV convertor. But I'd want a TC published format before I'd spend time on it. I'll look into this more later.

I'm kinda spoiled with Torque's interface on a 11" tablet. I can design whatever graphs/gauges I want, multiple pages if I desire, and easily datalog into csv files. K7 is downgrade in comparison, but the K7 is bi-directional.