Similar issue. 2007 Prius with 237k miles. Lately has given p0420 cat code 8 times since last 2 oil changes(6 months). Also , since last 2 oil changes noticed oil consumption is very high...800miles per quart. Changed PCV valve and Spark plugs yesterday. 2 of the spark plugs had oil in them. Other 2 we're dry. Today got check engine light. My strong guess is this is the p0420 ..with the spark plug change, some oil have seeped in, burned and got into cat. After spark plug change, I do notice acceleration is smoother . Before it would make weird sound(misfire?) in exhaust sometimes when I press gas. I use convention oil 5w30 Any recommendation considering I had oil on 2 of my spark plugs and my oil consumption issue ?
Ok. Any recommendation considering I had oil on 2 of my spark plugs and my oil consumption issue ? Pls see the thread above
Do any of the valve cover bolts seem loose? It doesn't appear too difficult to replace the gasket in this video, there may be better videos. For oil consumption, there are different suggestions and things to check if you read through posts, some try a 3 stage product set called BG 44K. I am trying to improve mine too, I used a cheaper engine oil flush, the idea is to clean up the crankcase and any stuck oil rings on the pistons so they start to work better again. Fuel system cleaner has helped some people and that is also part of the 44K kit, I just used a bottle of Techron. I replaced the oil with a cheaper synthetic and it seems to be staying cleaner and not burning as much.
If valve cover gasket was the problem, wouldn't I find oil in all 4 spark plugs ? In my case 2 we're dry and 2 had oil .
Check engine light off. So I am 100% sure it came because of p0420. Hoping new spark plugs, PCV will cause less oil consumption and permanently rid it off of p0420
I don't think they would all fail together since each plug hole has its own gasket, so it could be that just a couple failed. I would try to tighten bolts gently to see if any feel loose, or in need of tightening. If your two spark plugs with oil are next to each other it might be the bolt between them being loose. You might just be able to tighten or retorque them to specified torque and see if the oil stops leaking.
Well your not clear when you say oil on the sparkplug. If its the base of the plug above the threaded end the valve cover is bad pretty common but at the rate of consumption your seeing i assume you mean the firing tip has oil on it if so the motor is done. The piston rings primarily the top ring that manages oil is damaged or very worn. It probably has seen a few ran so low on oil the engine light came on events. Only takes a good one or 2 of those. New used motor time.
The 2 leaky SP were 1 and 3 starting from the left. So it can't be the bolts. Likely the Value cover gasket seal.
It’s pretty easy. Take off the wipers and windshield water dam will give you Plenty of room. Move the wire harness next to the cover on the drivers side over away from the cover unbolt and take it off. It will need some ultra black gasket maker at the metal seam where the timing chain cover meets the block just a little dab there on both sides on that spot then gasket is dry everywhere else. Must use dealer gasket. I found on my car the 2 small hoses that go from the cover pcv to the throttle body had cracked ends where they meet the plug into the cover so I replaced those 2. They have special tight corners an off the shelf hose will not work bend well without a manufactured hard bend so that was dealer replaced too. My Dealer had these in stock so common stuff, With cover off good chance to see how much wear is on the cams and chain How much slack the chain has. Good exploration. Take lots of pics for your records. As a side note with windshield dam out good time to flush out both water dumps. Keep tray free of debris if they clog up the water will overflow the dam and dump out right on top of the motor. You will never know till you stall out in the middle of a bad rain storm. They normally dump out behind each front wheel. Just put a hose inthe metal tray fill it up flush it out. Take advantage of the dam out.
Windshield dam tray removed pics: I was surprised to see how much crap was in there as I blew out tree debris almost daily with a leaf blower out of the tray. If you do not do that it may be very bad under. Can contribute to mold smell in ac with fresh air recirc on too. Take advantage of the disassembly situation.
There is a process that takes about 3 days to complete that super cleans your top end cylinders and pistons. You remove spark plugs and pour 4 Oz of acetone??? in each cylinder. Wait 24 hours and then pour 4 ozs of something else. Then fill engine with ATF and run it for awhile. Then fill with normal oil and new filter. I’ll search and find a link. I’m on my phone and can’t copy paste now. I have a friend that has a third Gen that I need to do it to.
I did a similar process recently. Running on ATF concerns me though. The process I followed, loosely: 1. Remove coils, plugs, etc 2. Pour 4oz Seafoam into each cylinder and plug with a rag 3. Wait 48 hours 4. Decide I should replace the valve cover gasket since there was oil on the 2nd plug threads (from the left) 5. Replace valve cover (and PCV valve, plugs, clean MAF and throttle body, lubricate a few things, etc) 6. Since I wanted to wait for the small amount of RTV gasket to dry, decide I should throw in 1oz of Marvel mystery oil in each cylinder 7. Change oil I did take some before and after pics with a borescope but didn't notice a big visual difference. Haven't driven enough to see if it changed my (minor) oil consumption at all. The valve cover job takes 2-3 hours if you move slowly. I hadn't done one before so it probably took longer. Remove the cowl, and carefully tie the brake fluid reservoir and engine wiring harness up and out of the way. I didn't have any issues getting the gasket to stay in place. Use a small bit of RTV and torque the bolts per spec. The service manual is very helpful here. My post with pics: Timing chain - slight slack between intake and exhaust sprockets | PriusChat
After Spark plugs and PCV valve replacement, did oil change. Since oil change have driven approx 1000miles (20% highway). Oil level still slightly below high. Oil Color is still like new(not golden brown color). I have not added any oil additive. So far so good. Still early and haven't done much highway driving.
And no p0420 code which I am now somewhat positive that it was related to oil consumption or a spark plug misfiring due to oil leak & rich mixture getting burnt and going thru catalytic converter triggering p0420
Got p0420 yesterday 1000 miles after oil change & the maintenance (spark plug & PCV valve replacement). Will continue to monitor if and when I get this code along with oil consumption (which definitely shows improvement).
High mileage oil burning car cat is probably contaminated very common on this site. I would replace the cat. my non oil burning G2 at 150k miles sold my oem cat bought a $125 cat off Amazon car ran much better.
Passed the smog test. Also, oil level still near high even after 2k miles since oil change. Only got p0420 once in last 2k. I bet changing spark plug and PCV valve did something good. As I noted 2 spark plugs had oil in it...There may have been misfiring & oil, rich fuel mix burning due to that. I also feel vehicle drives smoother now when I press gas & don't feel loss of hp Remember I started getting p0420 only 3 oil changes ago. May have gotten it 7 times in the prior 2 oil changes. And in both those 2 oil changes(ones before current oc) it was burning oil like crazy. The tech thinks PCV was functional.
