We have a 2005 Toyota Echo, manual 5 speed, with 160K miles. Everything works fine except for when you are accelerating (can happen in any gear) and mainly uphill. I assume the primary condition is when the car is being pushed or under more load than just cruising, anyway, it will will make a low grumbling noise and simultaneously shudders as if it is going to stall. This happens in a jerky fasion and doesn’t last very long but consistently under aforementioned conditions. We have 3 Echo’s by the way, all manual shift (Echo friendly
Scratching my head with a wrench in Florida!