Engine running very rough and CEL flashing

We have a 2005 Prius with 77,400 miles on it. My wife came home from a short trip yesterday saying the engine was shaking the car and the CEL was flashing. About 4 months ago we also had the CEL come on but not flash and it ran a bit rough but not as bad as it is now. I was told by our local dealer that a flahing light is worse than if the light comes on and stays on. When this happened 4 months ago at 74,000 miles the dealer said they downloaded codes P300, 303, and 304 and that I needed to replace all 4 fuel injectors. I realize that 300 is a general misfire code and 303 is a misfire code for cylinder 3 and 304 is for cylinder 4. After reading some advice on here 4 months ago, I cleaned my MAF sensor, ran some fuel injector cleaner through a tank of fuel, replaced all 4 spark plugs, and started buying Chevron gas. The CEL stayed off and our mileage went back to normal. I thought I had solved the problem but now this after 3000+ miles. I checked all the ingitors, connections, spark plugs, and wires yesterday and all seem to be in good condition. Maybe they were right and the fuel injectors are going bad. I am at a loss as what else to do other than take it back to the dealer now and plan do that this afternoon. Anyone have any other ideas?

 

Thanks for the input and I may end up doing that. As I was driving to the dealer which is a 20 mile drive the engine started running just fine again and the CEL stopped flashing. I have not yet had the Hybrid Water Pump replaced that has been recalled. So I called the dealer and told them I would bring it in tomorrow to have the pump replaced and get them to download the codes. Now today the CEL went off altogether. I thought it had to be either turned off by a computer or dissconnect the battery for 5 min. but obviously that is not the case. I may end up cleaning or replacing the injectors but for now it is running good again. I will also ask the dealer about it tomorrow to see what they think and see if they can still download the codes or not.

 

It is strange how it started so suddenly and then stopped very suddenly. I had checked all electrical connections or everyone I could find and they all seemed in good condition and well connected. It was almost like a piece of something got stuck in one of the injectors and then broke free but I really have no idea.

The dealer did not get any codes as the CEL had gone off completely. I am reluctant to ask them to do much as they seem uninformed at times. When I picked it up after having the Hybrid Water Pump replaced (per the recall) I asked them if they had also changed the coolant. Their first response was that there was no coolant to replace. After I asked them what they thought the pump was pumping then they checked and saw that indeed the coolant had been replaced. Probably a disconnect between the mechanic and the service advisor. I just have to trust that the mechanics know what they are doing but the advisors they let me talk to don't seem to know much of anything. I wish they would let me talk directly to the mechanic doing the work but they seem to want to build in that barrier between the customer and the actual work being done. I am sure it makes it easier for the mechanic but more difficult for the consumer.

I will keep using occasional fuel injector cleaner and Chevron gas and hope it doesn't surface again.

I still suspect that I could have caused some of this from having sprayed too much throttle body cleaner in the throttle body before I knew better quite a few months ago.