I inhereted this car from my dad when he moved the China. Super nice one too, very clean and well maintained. Now it's not running well and I don't know what to do. It started stumbling on acceleration from a dead stop only when warm. Cold starts and idle are fine. Now when in park and warm, the idle surges up and down. I changed the air filter, plugs, plug wires and engine harness. Tried some seafoam cleaner for the injectors all to no avail. Ran the codes since its a California model and got: DTC 5, 10 and 19.

I need some help on where to start and what to try next. Anyone help me out there?

Thanks.