Ok here's what happened: I replaced a failing two way coolant valve and went ahead and replaced the coolant. After this the heater wouldn't get hot, so figuring there was still air in the system I added more (which it took)...and repeated that twice. (and opened the top valve to allow it to bleed). Finally heat. I got up this morning and the heater still wasn't working....so I added more fluid....which it needed. Now I have heat. BUT, The engine started running like crap. Code says misfire on cylinder 1. Changed the plug and coil pack. This did not help. (When I pulled plug one out the end of it was dry.) Could it just be a crazy coincidence Immediately after I changed the radiator coolant that a faulty or clogged injector rare its ugly head? The car was running fantastic before this. I thought, before I check the codes, that some way maybe I overheated the car and landed with catastrophic issues. Alright guys.....where to go next??? I have 378,000 miles on my 07 pruius Thanks!
At 378K, pretty much nothing is a coincidence. If you are going to continue the shotgun approach, the injector probably would be next. After that, you probably need a shop visit for things like a compression and leak-down test.
A shop?? hmm what is that? I may have to. I will obtain a new injector and see if that helps. Overheat? That thought ran through my mind too, but I didn't detect anything "hot" under the hood. No sign of that anyway. The coolant was luke warm at its hottest. The engine didn't appear hot in any way. I drove the car the majority of the day today. I really want to get 400,000.....If I can, then I win! This is personal....but I think I've already won big time with 378,000. Any other advice appreciated.
Well, did you actually drive the car while the engine coolant was low? If you were only working on it while parked in your driveway, I doubt the engine had overheated. But if you drove at 75 mph for 100 miles while the coolant was low that certainly could cause permanent damage.
First just try switching the injector on the misfiring cylinder with another one and see if the misfire moves. JeffD
Thanks Patrick. No, I drove down the road, maybe 5-10 minutes. The least amount of fluid I had in the system was over a gallon. Probably the Injector I inagine is the culprit. I will swap it tonight and drive to work and have the codes rechecked. The timing was just really strange and the fact it has been running so well till last night.
I assume that the logged code is DTC P0301. If you had drained 6 quarts and added 4 quarts, then you were low 2 quarts. That would explain the cabin heater not working. Make sure the wiring harness connectors to the spark igniters and fuel injectors are properly seated. If that doesn't help then I hope you will find that the cylinder 1 injector is the problem. If you had a problem with more than one cylinder I would suggest you check the fuel line pressure which should be at least 43 psi at engine idle. Otherwise the next step would be to perform a cylinder compression check (using Mini VCI to get the engine to spin) or else a cylinder leak down test.
Upate: I went ahead and replaced ALL the injectors and ALL the spark plug igniters. Plugs were replaced a month ago. I still have misfire on cylinder 1. I will do what Patrick said and do a cylinder comp check, but is there anything else that might be causing this misfire. This misfire, like I said, started immediately after I replaced the 2 way valve at the radiator. Is there anything in this vacinity I could have disrupted to cause the misfire? What about any sort of vaccum hose? I didn't see anything disconnected. At idle, at times, it sounds like the transmission is going to drop out of the car! I got under the car today and listened and observed and I've been told the transmission does this when there is a misfire. Crazy. It rattles and knocks horribly. I should say the motor when idling runs well at times for short durations. Like maybe 10 - 15 seconds, but invariably returns to the horrible shaking---Misfire. 379,000 miles. I am not ready to give up! I was able to pick up the injectors and ignighters for free btw. I know a local guy who buys and sells wrecked prius and rebuilds. Thats where I got mine.
It is possible that a bad wiring harness connecting to the cyl 1 spark igniter or fuel injector is the cause of the problem. Or the engine ECU might be (in rare occasions.) The engine and hybrid vehicle ECUs are both located behind the glove box, to the right of the cabin air filter. I am not aware of anything around the engine coolant valve which would contribute to an engine misfire.
The air in the system probably air locked the coolant that was there from circulating which is why the coolant you could get to never got warm. I had this happen to me once on a motorcycle back in the 90s. The air trapped preventing the coolant from circulating and the engine over heated warping the head which then caused a leak between the cylinder block and cylinder head pulling in cooalnt causing a misfire.
I am wondering why you have a misfire on cylinder 1 but you measure low compression on cylinder 4. I am also wondering why you observe the engine idling OK for short durations. A low compression issue should be continuous, not intermittent. Cylinder 1 is closest to the passenger-side fender; cylinder 4 is next to the inverter. The next step is to inject a couple ounces of engine oil into the cylinder with low compression and see if it improves or not. If no, then the valves are the problem. If yes, then the piston rings are the problem. Either way, the cheapest repair would be to install a used engine if you want to put more money/time/effort into this car. Otherwise, tow it to the salvage yard and be done with it.
