2005 Prius bad EGR valve?

There is no EGR system on Classic or 2G Prius. I suggest you obtain the diagnostic trouble codes and see if engine misfire is the only issue.

 

Hi I have a similar problem, did you ever figure it out? My Prius has had rough shutdowns for a while, but it hadn't bothered me much. But on this last trip (about 3000 miles), it got a lot worse. When I got to a stoplight, the engine would just sputter, like it was misfiring, for a long time, shaking the car. The final straw was that while driving, it began to do (what feels like) the same thing. But only in very specific circumstances. It seems to only do it at like 0-25% throttle. Anything more and it runs smooth. But with light throttle, it just feels like it is misfiring all over the place. When in cruise control, when we come up over a hill and start going down, it would "misfire". But if I either step on the gas, or turn off the cruise and coast, it is smooth. I've been doing a lot of searching, but haven't found anything that sounds quite like what I'm experiencing. No check engine light. 2007 Prius, 377k miles.

I found a video of something that sounds similar to what mine is doing, but mine is just doing it a LOT more.

 

If there is a problem with your foot off the throttle (ie at "idle"), then clean the throttle body and the Mass AirFlow sensor and see if that helps. While you are thete make sure that the oil and coolant levels are good.

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Hey, thanks. I think it actually idles fine... Ie the ICE runs just fine at idle. It's when it wants to shut down that it gets really weird. Starts clunking all over the place.

Same when driving, if I am coasting, it will idle just fine. If I have it on cruise, and it's right in between throttle and no throttle (like just starting to go down a hill), it does the same clunking thing.

I'll take a look in the throttle body either way. Oil level always stays constant, as does coolant level, but I'll double check those as well. Thank you for your suggestions.

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Clean the throttle body! A dirty throttle body on a gen2 is known to bother the computer and sometimes make the ICE not shut down like it should. It’s a very easy job, lots of videos on YouTube

 

Excellent! Thank you! Will clean the throttle body and report back!! That does sound like a likely culprit to me.

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Edited to indicate I cleaned MAF, not EGR. Sorry y'all! Mistyped that one

UPDATE: Cleaned MAF and throttle body and it seems to have completely fixed the issue (based on a short test drive). ICE start and shutdown are smooth. No clunking or weird behavior while driving. Thank you for the suggestion!

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Awesome!! Happy to hear this. Good work

 

g2 has no egr.

 

As stated a few times in this thread, the Gen 2 does not have an EGR system to be cleaned.

Perhaps you mean you cleaned the PCV valve.

 

Thanks, yes, my mistake. I meant to say I cleaned the MAF. Dang acronyms.

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I cleaned the MAF while cleaning the throttle body. I think I was on auto pilot and put in the wrong acronym. Woops!

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When you pull the air filter Box off to clean the throttle don’t forget the sneaky pipe clamp under the box that clamps the box to the throttle body bore.
It’s a 10 mm bolt head. And spray some lubrication on the return spring.

 

Just need to UPDATE again and say that after a longer drive, the problem is NOT fixed. Still trying to figure it out. Please check out my thread for a video of the car running. Rough, Long Shutdown, "Misfire" on Light Throttle | PriusChat

Rough, Long Shutdown, "Misfire" on Light Throttle

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Considering the car has 377K miles, I suggest you check engine compression to see whether the engine is in basically good mechanical condition or not.

Look for an air leak in the engine intake air system. In post #14 above, Ed pointed out one place where an air leak might occur. Also look for a leak anywhere in the system between the mass air flow sensor and the throttle plate. Make sure the engine oil cap and the engine oil dipstick both have good O-rings sealing them. Ensure the PCV hoses are tightly fitting and the rubber has no cracking.

 

Thanks! Great idea. I'll take a look at those tomorrow. I do think the intake is sealed up nicely, but because I saw some oil inn the intake when I cleaned it, I suspect the pcv might be stuck or leaking.

I'll be interested to see how the compression test goes. It uses almost no oil, which I've interpreted as it being fairly healthy, but I guess that's primarily the rings, definitely could be an issue with the valves.

Speaking of the valves... When I did the timing chain, I pulled the vvt sprocket apart... I wonder if it could have something to do with that.

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It is normal for hydrocarbon fluid residue to deposit in the intake manifold at the bottom of the throttle body. The source of that might come from engine oil via the PCV hoses and also may partially come from gasoline vapor. The Prius engine uses Atkinson cycle, where during the compression cycle, the intake valves for a cylinder are not fully closed as the piston starts to compress the fuel/air mixture in that cylinder. Hence, some of the fuel/air mixture can exit the intake valves and deposit in the intake manifold.

If the PCV valve has not been replaced in the last 100K miles, I suggest you do that replacement now. If the valve is remaining open when it should not be, that would cause a lean fuel/air mixture which might be the cause of the driveability issues you have noticed.

 

When you say "apart", what are you saying here, exactly?

 

When I was replacing the timing chain, there was basically zero information available, since it's supposed to be a lifetime part (mine had stretched out of spec). The cam sprocket on my Prius rocked back and forth freely, whereas I watched some videos of camrys and there is a retaining tab that is supposed to lock it in place. I searched and searched to try to find any documentation that indicates that the Prius sprocket should rock freely, but couldn't find anything. So I brought the sprocket to my bench and opened it up completely and verified that it was not broken, just operates differently than a camry. You can see it apart in my video below at about 5:35. I just don't recall what I torqued the bolts to, and I'm pretty sure I didn't use thread locker and I've worried about that! I guess it wouldn't be that hard to pull the valve cover off to check.

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