Intermittent warm start issue - cranks, starts into low idle and dies.

Three times over the last couple months, all on warmer (>75 degree) days, my 2020 tundra with 40k miles has refused to start (always on a warmed up engine).

The truck turns over strong, starts into a low/rough idle, then dies after a few seconds. Subsequent attempts just have it crank and crank and crank with the occasional start into a bad idle. It dies right after.

The first time it eventually started after 10+ attempts over 30 minutes. The second time it only gave me trouble for a couple of tries before starting up into a bad idle Two days ago I had to leave it in a parking lot and walk home. The next morning it fired right up after a long crank.

Other than this it runs perfectly. This screams "spooky fuel issue" but it's so intermittent that I have no idea how the dealer is ever going to track it down.

No codes beyond one for 'rough idle' and 'failure to start'. Dealership hasn't been able to figure out what's wrong.

Anyone have issues like this? I've read of similar sounding issues on older 2nd gen tundras related to fuel density calibrations, but don't know if that applies on my non-FFV 2020...

 

I would probably go down the route of a battery issue, it may be on its way out. When I use to jump my battery, it would do similar things as you stated. I would start with getting the battery tested to ensure it's still good but consider its short-term replacement. Secondary would be a fueling issue. Maybe the fuel pump ECU or Resistor towards the bed of the truck I believe. Also consider changing gas stations, just in case there's more water in the system than fuel. For example, my Celica and Tundra after getting gas on base would stall out after the mile stretch leaving the base, would idle rough and stall out. Once I started getting gas everywhere else the issue was resolved.

 

Well, fortunately it was warm enough today that the dealer managed to replicate it. They pulled the fuel rail and no fuel was flowing while this was happening.

Turns out there's a TSB related to the fuel pump (I'd love to read this if anyone has access or knows of it). On warm days the pump can fail without the ECU being aware of the issue (hence the lack of useful codes). New pump should be here on Monday, so hopefully (fingers crossed) that fixes the issue.

 

If it gives you trouble after the fuel pump swap - take a look at this thread.

https://www.tundras.com/threads/fue...side-circuit-voltage-drop.63638/#post-2504951