Hi all, I have a 2012 Prius with 215k miles on it. It was having issues with misfires previously, so I cleaned out the egr valve, the little holes on the manifold, the pipe in between and the cooler. The misfires went away for several months and everything seemed to be fine. However, recently the car has been acting up again and again I cleaned out the intake and egr system. There was not much carbon build up and the valve appeared to be moving freely. I also removed the MAF sensor and wiped it down. It was coated in oil and there was oil in the catch area below the MAF sensor. The misfires went away for a little while and the situation appeared to have improved significantly. About 2 weeks later, the misfires came back with a vengeance occurring more and more frequently. The two factors that changed here are the weather got colder (35-50F) and it was after getting gas. The gas was purchased from costco, a reputable gas station. I unplugged the electrical connector to the egr valve and the misfires remained. (which should rule out the egr system). I marked the coolant level with a sharpie on the reservoir, drove the car for 25 minutes and it was nice and warm, the coolant level remained the same. The codes that come up are P0300, P0301, P0302, P0303 and P0403 (because I unplugged the egr) The misfires are "random", however it appears they occur more frequently if the car is not warmed up and if the car is under gentle acceleration. Light acceleration doesn't appear to produce the issue, nor heavy acceleration (if you stomp on the gas). If there are misfires, you can either let up off the gas or press harder and the misfire will disappear. Once the car is warmed up, the misfires are very infrequent. I would think that if it was a head gasket issue, that the misfires should be worse when the car is warm, as the coolant temperature and pressure is much higher. It shouldn't be an egr issue since that system is unplugged. I don't think its a spark plug or coil issue since its occurring on 3 out of 4 of the cylinders. My expectation would be that it would only be one (maybe two) cylinder if that was the issue. I'm thinking the MAF sensor is plugged or clogged, or its has bad gas? Maybe something to do with the cold and condensation build up? Any thoughts?
Those codes indicate misfire (on cyl’s 1 thru 3). EGR code is diff, P04xx IIRC. That’s good, but late in the day. If you mean the sensor down low in the intake manifold, that is MAP (Manifold Absolute Pressure). If head gasket is leaking coolant into cylinder, it tends to be worst at cold start ups, because the leakage is slow, more coolant collects in cyl’s overnight.
I can stick a camera into the cylinder. Better to do it when its cold? What should I be looking for if its a bad head gasket? Coolant on the cylinder head/ walls?
It's apparently tolerant of being oily. The real MAF, which is up in the horizontal air duct near the top of the engine, is not.
Just like the rest of us but he does have years of dealer training and experience to back it up. 5k oil changes from day one - yes, shortcut cures for oil burning and head gaskets - no.
I sent this to my mechanic, he says: I would perform a sniff test on coolant to check for head gasket and also check purge valve operation.
Stuck a camera down there, anything look suspicious? I see some pinkish reside, but it is not obvious to me if it’s pink coolant.
