Cold start issue: 2.7L Stumbling/Stalling UPDATE: Fixed

Still trying to narrow this down...rather frantically now that it's getting warmer and it seems to only really do it when temp is 60 deg +

I was unable to recreate the bad RPM reading on my scanner. However, I have narrowed it down to an event that I seem to be able to replicate...filling up with gas. Tank is on E, drive about 5 mins to gas station, fill up. Turn the key, its stumbles to life at 500 RPM then dies. After that I can crank and crank and crank before it starts again (usually about 15-20 sec). Holding WOT seems to make it start quicker. This has happened to me about 4 or 5 times now, each time it's the exact same scenario. This starting to sound like a vapor issue, fill up with fuel and vapors are pushed into the intake due to bad solenoid thus flooding the engine. WOT allows it to start cause it's adding a lot of air and clearing the combustions chamber. I am going to try to test my purge valve and VSV tonight and I will report back. Thoughts, ideas?

 

Both evap solenoids seem to be okay, they open when given 12V and close when deenergized. Only weird thing is one of the solenoids is getting 3V when closed, should be 0V I believe. Going to run fuel system cleaner through it then get a fuel pressure gauge and try to troubleshoot and try to rule out fuel pressure regulator and injectors.

 

So it's been two week with the fuel cleaner in and since I took out both evap solenoids, cleaned them and cycled them. I have not had this starting issue since then. It's been very hot past few weeks too. I will see if I have the issue when I fill up with gas in the next few days. I'm gonna call it fixed, fingers crossed.

 

Turns out this was the charcoal canister. It took 2 years but eventually I got a CEL (P0442) for this, so I finally decided to troubleshoot it cause my state inspection was coming up. Some internal check valve or diaphragm was letting the fuel vapor pressure make it's way into the intake through the "Canister Closed Valve" which is normally open. Therefore this issue would present itself during hot days after the truck has been sitting or after I filled up with gas...vapors were forced into the intake. Other symptoms were that I could not fill up the truck with gas while it was running, it would immediately shut the pump off.

I replaced the leaking gas tank and a few other things a few weeks ago and then the truck would stall after sitting on a hot day...it hadn't done this since around the time the CEL came on. CEL came back on after these repairs so the charcoal canister was the last piece and was luckily under warranty still. Replacing that fixed all the issues I was having.

More details on this issue as well as troubleshooting here:
https://www.tacomaworld.com/threads/strange-evap-issue.732305/
https://www.tacomaworld.com/threads/p0442-repair-troubleshooting-log-and-smoke-test.843788/
https://www.tacomaworld.com/threads/how-to-techstream-evap-test-p0442-and-p0456.843787/

 

Great job and thorough follow up!! Thanks for taking the time to share it all here.