A month ago my prius started misfiring(with bad odour like rotten egg) without any warnings and firstly I checked the spark plugs, all 4 seems ok(no oil no moisture, all seem to working just fine) but I changed all plugs, even tough I changed it was still misfiring then suddenly the misfiring is gone, the misfiring has been happening randomly until yesterday and now it is permanently misfiring(still no check engine or any other errors on the dash) I did following things but it is still misfiring. 1. Changed all 4 spark plugs 2. Cleaned intake manifold 3. Cleaned egr and the pipe 4. Checked all injectors(all seems working) and tested all injectors with battery and carb cleaner Since there is no error I am just trying to figure out the problem myself, also since all spark plugs look the same(working) it is difficult to know which cylinder is misfiring, and now I just do not know what to check. Any ideas?
Sounds like your catalytic converter could be bad. They clog up and that would cause the engine to run rough and explain the smell.
How many miles on your Prius? How many miles since you did all the cleaning? Was the intake manifold clogged (particularly the egr inlet to the intake manifold)? Does your Prius consume any oil?
200.000 km now, I did all the cleaning yesterday so zero running. I would say intake manifold egr and egr pipe was not that bad as it in youtube videos cleaning all these. I check the oil regularly and no it does not consume engine oil
When you pulled the egr off, did you try and actuate it? Clean the throttle body? MAF sensor? Has it displayed any lights on the dash?
Could it be a hairline crack in a spark plug coil pack socket? Not sure if increased unburned fuel into the catalytic would liberate hydrogen sulfide but maybe with increased temperature. No codes and no misfire code. Mystery.
Up until a few days ago I never even considered a bad fuel pump in diagnosing lean conditions or misfires in a Prius. Then we had reports here of a complete failure and a weak one within a few weeks of each other. Model years were 2010 and 2011, 193 and 155k miles respectively. Too early to call this a common Gen 3 failure but worth a look for you if all else fails, I guess. P0171 | PriusChat fuel pump | PriusChat
the mystery is solved, it was egr valve clogged and stuck open so it was causing the misfire. Took it off and cleaned it with carb cleaner and now it is good.
That's good to know. A lot of times people will ask for help then just disappear from the thread, leaving all the posters high and dry as to the outcome. Thank you for getting back to everyone and sharing your results. It's great information for the next guy who might have a similar problem. That's what the Forum is all about.
