I’ve spent a lot of $$ trying to fix a persistent problem on my 2000 Toyota Sienna CE van. Engine chugs at idle & low speeds, then accelerates suddenly (when rolling, in gear). Have tried: changing timing belt (+ water pump), cleaned fuel injectors, replaced all of these: crank sensor, fuel filter, spark plugs & wires, ignition coils. $1800 later, nothing has worked. My usually spot-on small-shop mechanics (2 different shops) are baffled. It still (sorta) runs, but the sudden acceleration is a hazard in traffic & it’s not reliable–maybe not even safe anymore.
Local shop ran full diagnostics at our expense. Code results: PO 301, PO303, PO305, PO1717, PO171, P0172, P1130, P1150. Translation: Cyl.s #1,3,5 misfiring. Fuel trim lean, bank 1; rich bank 2. (This prior to sparks & wires replacement.) They recommended replacing both A/F ratio sensors, which would run another $700 (at their shop, book rate). Did not authorize repairs, as I don’t trust this shop & my other mechanics doubted this was THE cause of this problem. Reluctant to spend another $700 if that repair is not likely to resolve this issue. Any ideas?