My prius (189k on the ODO) started shuddering all of a sudden as I was driving and the check engine light started flashing on and off. The CEL has not remained solid. The shuddering got worse under acceleration. I immediately checked the coolant level and it is still at the full mark. Where should I begin? Replacing the coils, spark plugs, egr valve, egr cooler, intake manifold? Took a picture of the dipstick... someone said it sounds like it's out of oil but it seems like there is plenty. Also, if anyone is near Yorktown VA, I would love some help as I do it and can offer compensation to mane sure I don't miss things. Thanks!
start with cleaning the egr circuit. it's free, but time consuming. lots of video's online. if you want to make sure it's not the headgasket before doing all that work, you can perform some tests or have a shop do it.
Likely a waste of time now. I'd get a boroscope inspection of the cylinders with the coolaning system pressurized, looking for tears of coolant seeping past the head gasket. Also look for any piston tops lookiing oddly clean (it tends to be cylinder one or two). Leak-down test is also good: you manually crank the engine till a piston is at Top Dead Centre on compression stroke, apply air pressure to that cylinder, using a special leak-down gauge set. Shops that have the equipment and know-how will know what you're talking about. Once the head gasket is assessed, and likely replaced, then I would follow up with cleaning the EGR and intake manifold. It's best done every 50K miles.
These are the 7 codes that popped up, I know some of them are duplicates but thought I'd include them. Gonna test the battery and alternator to see how those are holding up p0302 p0300 p0304 p0302 p0300 p0302 p0304 c1241
Any specific tests I can do? I was browsing the forums and saw someone recommend a liquid in the coolant that could change color if exhaust fumes are present. They just didn't name the product
idk if there's a 100% positive test. i've heard leak down, boroscope, there are a few videos out there: watch
Combustion gas in the coolant, compression and leak down tests rarely work as a hg diagnostic on a gen3 Prius. A borescope test is the most conclusive with the coolant under pressure. Using a dual view borescope, eg not a cheap one. If you were getting one cylinder misfires rather than multiple per your codes you could look at coils and plugs by switching them and watching for the misfire to change cylinders. Multiple is typical of hg. The only thing not making sense is your lack of start up rattles. If you had them a few times and they cleared up, that was typical early hg behavior. If you had those and now its worse your engine is at risk. Don’t parts cannon it and lose the engine or waste a thousand dollars. Typical Borescope Test Car Care Nut HG Borescope at 10:57 He starts by looking at a spark plug. He mentions egr as a possibility. Only if stuck open as an egr normally closes at low rpm or startup. Stuck open egrs are not typical on a Prius that tend to clog egrs. But an egr that is stuck open will stay open and not quickly clear. In mid 2014 Toyota revised pistons and rings which helps hg frequency.
One simple&easy test you could do is to test whether egr valve stuck open. You only need thin metal plate you use to block the egr flow. That same Car Care guy has a video showing how to do it. I had valve stuck open and engine was rattling and shaking. A lot.
Was your engine throwing misfire codes? Mine has misfire in 2 and 4 and the miscellaneous misfire code as well
No, just P0401. Nothing else. I hear it’s rare to have valve stuck open in Prius but happened to me. i noticed your coolant and oil levels were in the max level if not even beyond. How long you’ve had the car? In long term its not good to have too much oil. Dipstick also very readable. What oil you’re using? Never had that well readable dipstick reading with Prius
