2011 Prius P0303 misfire

Hello everyone! I am in the process of troubleshooting a cylinder 3 misfire on my wifes Prius. The code has been showing up for the past month or so. I finally got a chance to troubleshoot this weekend. I changed out the spark plugs with Denso plugs, changed the cylinder 3 coil with a Denso coil, cleaned the egr pipe and the spots where the pipe connects (which wasn't too bad), and the throttle body (which was pretty much spotless). The spark plug on cylinder 3 was white and ashy. We get to driving the car and it is still randomly driving rough. It has popped p0303 yesterday after all of this and I cleared this. This morning the code has popped up again and I'm thinking the next step would be fuel injectors. Has anyone run into this and if this could be an injector where would they be located on this car?

 

Hey Chapman! Thanks for this link! I have searched youtube for the procedures on this and nothing really came back for the fuel injectors on the Prius. I may call our local shop and see what they'd charge. It may be cheaper to have them do it right the first time lol. The main concern I have at this point is the location of the fuel injectors. My wife and I both looked around the engine and didn't see the fuel rail so a little help would definitely be appreciated! If they aren't too bad to get to I may try and tackle this.

 

Danlatu, we've checked the oil and haven't noticed any milky look or oil levels rising. Also the coolant level has not changed. Are there any other signs or symptoms I should be looking for?

 

Hey JC I'm pretty positive I did. This was the only plug that looked out of whack also. Here's the engine layout (I think)

Oil Cap- Cylinder 1- Cylinder 2- Cylinder 3- Cylinder 4. The wiring looked good to the coils from what I could see

 

It's around 155k-160k miles

 

The only code that keeps popping up is P0303 which is cylinder 3 misfire. If I could get some help locating the injectors I would like to try using the old screwdriver stethoscope trick. If they're a pain to get to I wouldn't mind getting a tester also and such. I'm really thinking it's something with the injector tbh. It may just need to be taken off and cleaned or swapped out in general. I'm comfortable doing either though

 

I have been looking at Prius engine diagrams and have circled the area I believe to be the location of the injectors. Is this correct? If so that would be the front of the engine and should be pretty easy to access.

 

Thanks danlatu! I will go ahead and test the injectors tonight via meter and the screwdriver stethoscope test. If they pass I will test for head gasket next

 

I wanted to give everyone a heads up. Life has been very busy. We dropped off the car at the mechanics this morning and the oil is a little low. It's going to go ahead and get an oil change while it's in there so they can continue diagnosing. After this though I think I'll be using mobil 1 high mileage 0w20 for 7500 miles. I believe that is a full synthetic. Anywho I listened to the injector on cylinder 3 and it sounded good. I have a junk meter and the readings were bouncing all over the place on the injectors (tested more than 1) At this point it's honestly cheaper for me to have a mechanic look at it than throw more parts at it just guessing. Even if it is the injector at this point I'm not comfortable swapping it out.

 

The mechanic said this was the intake manifold and it needed to be updated to the new one since toyota had a tsb. Did that and no luck. Still running like crud (bumping on deceleration) and now we are out around $1k. They said they still didn't think it was the injector but to drive the car this weekend and see if it relearn the air/fuel ratio. I asked about the head gasket and they said they didn't see any head gasket issues but will test via putting each cylinder under pressure Monday if this issue still continued.

 

The issue is much worse now. Car is back at the mechanic and they are going to try and get compression tests run today. Hoping this is something simple....

 

Looks like I was right all along. The mechanic moved the injector from cylinder 3 to cylinder 1 and the misfire moved over to cylinder 1. They said they pulled the injector off the car and cleaned it. Most likely was done in the diy youtube parts cleaner fashion. They said that some crud did come out and the misfire seems to have disappeared. The wife is driving the car now. In the meantime I've been looking around for a matched set of 4 injectors in case this is only a temporary fix. Fingers crossed we are good to go though! Best case this happens at a time I can pull the injectors myself and send them off for a proper cleaning...Worst case I order a matched set of 4 matched denso reman injectors from ebay and just put those in. Either way we're riding this out for as long as we can. Hopefully this helps someone else going through the same issue!

 

Misfire came back. I ordered a set of 4 denso reman injectors from eBay w lifetime warranty. Mechanic had the gall to charge for labor after spending a grand and making the issue worse. Needless to say I swapped the injectors myself yesterday. The one that was causing the misfire was visibly discolored on the end. So far so good with the new injectors. We are going to give it a week or two before calling this resolved. I'll be shipping the original injectors off for cleaning sometime in the next few months so there is a spare set on hand. Either way we will be using top tier fuel from now on and I will be running some redline fuel system cleaner through there to clean up whatever carbon crud was caused by this misfire. Btw I did crush the top seal on the cylinder 1 injector on install and fuel sprayed everywhere lol. The seals on the old injectors were still pretty pliable so I just used that on the one injector. I'll probably leave it be and carry on! So far car runs better than it ever has! I'll keep everyone up to date with a follow up in a week or two.