Prius (2004-09) :: Check Engine Light With PO301 Cylinder Misfire Code

I bought my 2008 Prius 9-14 with 29,000 miles on it. (rebuilt title-big mistake I now know). I found out after I bought it that it had sat for 5 years before it was rebuilt) I figured it was a miracle the hybrid battery even worked.

I had no problems until 2-4-15 when check engine light was flashing and the car was shaking. The local mechanic said was the “clutch” (torque converter), took the engine and transmission out of the car to fix it ($2200). But he realized the mass air flow sensor (MAP) was not working even after he put a new one in so had me take the car to the Toyota dealer. The dealer found a cut in the engine harness and advised me to replace the harness which he said would cost $2800. The local mechanic saw the cut via my cell phone photo and offered to fix it for free which he did.

The next day check engine light comes on after driven 25 miles with code PO 301. (means misfires in cylinder one). The local mechanic switches cylinder 1 with 4, same code the next day, local mechanic switches the coils to the cylinders, still the next day the same code. He switched the fuel injectors. Same problem of cylinder 1 misfire. He cleaned the oil out of the intake manifold, did fuel injection cleaning, and cleaned gunk out of the fuel line. Car would drive good about 20 miles then same check engine light, same code, sometimes code PO300 (random multiple misfires).