Hoping for answers...bought a 2000 4runner, 3.4 about 4 weeks ago. Ran fine and my mechanic did a once over a a test drive. Passed state inspection with one minor find...a dent in the fuel tank about where the fuel pump resides. More on that later. Car ran fine and then developed an unusual symptom of engine running rough and near stalling after the truck had been shut down for 10 minutes or so. This event would only happen after engine was warm and then shut down, wait about 10 minutes to 20 then restart and the stalling event occurs. Runs fine cold and fine as long as you don't shut it down. Now for some history. This is a new/used motor in the vehicle. Previous owner had a timing belt go and then of course the engine. He bought a used engine and put new timing belt, water pump, radiator and gaskets for installation. The catalytic converter looks new and I installed new exhaust. I also installed new fuel filter, fuel pressure regulator, PCV valve and engine coolant temperature sensor. When removing upper air intake to replace FPR I found a very slight residue of what looked to be engine oil laying in the intake. It was not puddling, but enough you could reach down and find some to wet your finger. The inside of the intake had a very light film coating its interior. I have purchased a used fuel tank and am refurbishing it to new specs and will inspect fuel pump when I drop the tank.
After replacing FPR, PCV and coolant temperature sensor, I also cleaned and adjusted the IAC, the vehicle ran absolutely perfect for several hours. Starting and stopping with no stalling. I even had positive pressure in the gas tank which I did not have prior to repairs. Oh also you could hear and feel the vehicle surging ever so slightly while accelerating. That also went away after my repairs...but...while I was driving I got some pretty strong fumes of gas coming into the cabin and the truck continued to run fine. Inspection showed no leaks. waiting 15 minutes go back into truck...started it up and back came the rough engine and near stalling. Well I've typed enough...any ideas?