ACE1252,
I am sure that the vent line not was clogged.
Before I removed the Opti to check the screws, I tried to secure that it not was any moisture in it. I used my compressor at low pressure and pushed dry air thru the ventilation hose all the way to and from the opti.

Injuneer,
Thank you very much for your digging in my logfiles.
I also have seen this pattern and I am very curious to see if you can found any reason for this behavior.

/Lars-Gunnar

 

The Opti vent line, from the Opti to the intake manifold has both a flow limiter (orifice) and a check valve.

Looking further at your long term fuel trims, they switch rapidly from deducting fuel at idle to adding fuel as engine RPM and engine load increases. Have you ever checked the fuel pressure, while driving on the road? It seems possible that the fuel pressure is not adequate to meet the higher engine load/RPM combinations, and and as pressure drops, the PCM is using the LTFT's to increase the pulse widths to deliver adequate fuel. There is a fuel pressure test port (Schrader valve) on the fuel supply line (at least there is on an F-Body, but Corvette should also have one). This is just one possibility that I can think of.

As mentioned earlier, every time the PCM is operating in Cell 15 (above 80 kPa MAP/above 2,000 RPM) the EVAP purge system is at or near 100% duty cycle. If you have a vacuum leak on the canister side of the EVAP purge solenoid (F-Body, it's on a bracket on the passenger side of the intake manifold) it would cause a leaning of the fuel mixture whenever the EVAP purge solenoid is activated. Again, just a possible cause, and something to check.

http://shbox.com/1/evap_sol.jpg

 

I have measured fuel pressure and it is 42psi before cranking, 34psi at idle, 43 psi at 100% throttle high speed, 33psi at 0% throttle high speed.
If I understand the log files right, the high LTFT correlates most to TPS and BLM Cell.
See the attached log file where I think that the correlation to EVAP is not that strong.
I will try to block the hose to the purge valve and test again.
The engine is still behaving well. No surging idle and no hesitations during acceleration.
It is two weeks since I used the cold spray and I cannot recreate the fault.

 

I maby have an explanation to why the LTFT increase at high throttle values.

We have 5% ethanol in our fuel in Sweden and ethanol have lower energy than gasolin so the pcm must add more fuel by increasing the LTFT.

 

US fuel typically has 10% ethanol, and it doesn’t cause a problem. While it does affect the stoichiometry, requiring about 3% more fuel, the % extra fuel would be the same in all cells.

https://www.eia.gov/tools/faqs/faq.php?id=27&t=10

Generally, +/-5% variation in LTFT's is acceptable. I scroll through the data logs, and record the LTFT's in each cell. Your log was good, in that you actually drove in almost all of the cells, and the LTFT’s in each cell were stable, and well developed. Then I enter the LTFT's in a grid defining the cells with RPM on the X-axis and MAP on the Y-axis. Your data has a very clear pattern of uniform increase in LTFT's from the lower left corner to the upper right corner. (I'll try and post a scan, but my scanner is not communicating well with my new laptop). At idle, the LTFT's are subtracting 5% of the “normal” fuel, In Cell 15 (high RPM/high MAP) they are adding 15%.

I'll give your 5% ethanol theory some additional thought, to see if there is something I am overlooking. Fuel pressure is good, so that isn’t a factor. And it's running well, so maybe that is the only thing that is important.

 

Just so you can see what I am doing with the data. I transferred my hand written notes to the Excel spreadsheet, and saved it as a .pdf