When to Change PCV Valve ?

It's probably fine, the kind of thing you might do once in a vehicle's lifespan, often just as a precaution. I'd vote 100K.

My son and I did his on an 06 civic with 212,000 km's. Again it was likely still ok, but there was symptoms: there's a secondary PCV hose between the air intake (downstream of air filter) and valve cover, and there was some oil around it's connection at air intake. Also the air filter seemed to be overly oily/dirty, and the car's oil consumption is climbing a bit.

All of these could be PCV valve related so we thought to try that first. Had a bear of a time getting at it, especially while avoiding intake manifold removal. Ended up buying a $40 long reach, ratcheting wrench to facilitate that, and luckily it did the trick.

 

It's pretty rare for one to fail, but not unheard of. They can stick open or closed. I have read reports of new valves improving fuel economy by a few mpg. I would say that, if you're not having problems, it can probably wait till 100k. But, of course, ymmv.

I replaced mine along with the spark plugs at 148k because my mileage had slowly gone down by about 3-5 mpg. It came back up, but I'm not sure what helped the most since one of the plugs looked pretty bad. I also cleaned the throttle body while I was in the area. I got the car with 121k on the odo and don't know if or when either had been replaced before.

Doing it when replacing the spark plugs saves work since removing the coils on top of the plugs helps move the wiring harness out of the way so you can get a socket on the pcv.

 

I can't seem to figure out why my 2005 cars vary so much in mpg. My best one gets about 55 mpg, my worst one with 17 inch wheels gets about 40. Only thing I haven't changed on it is the PCV valve. Maybe I have to change that and see if anything improves.

I don't think it's a worn engine as the car only has 110k miles. The one with the great gas mileage has 183k miles. Very puzzling.

 

Have you checked the rear wheels to see if the drum brakes are dragging?

Also, are the two Prius used for similar routes, trip distances, average speeds etc.?

 

I've checked the brakes and it's not dragging. The one that has higher mpg is on the highway more. But I can't see a 15 mpg difference. Both cars have really good power, engines are in great shape with very little oil burning

 

Simple solution: just get rid of one of the cars, lol.

I had a twin exhaust bike like that: one pipe lean, one pipe rich. Drove me nuts. Trade to one with a four-into-one exhaust.

 

So now one pipe lean and three pipes rich, 2 pipes lean and 2 pipes rich, or 3 pipes lean and 1 pipe rich?

 

That is quite a difference even with the 17" wheels, @JC91006. Of course we've both been seeing plenty of people wondering about their low fuel economy. I'm not an engine mechanic, so I don't know if the pcv valve would make that much difference in fuel use or not. I kind of doubt it. But it's not really that hard to change and not expensive. You could be our guinea pig.

 

How about checking front wheel toe-in?

 

I haven't checked the alignment, it seems to track straight. I'll check that on my next oil change. Thanks

 

I've changed PCV before, twice, and both times I found the old PCV to be in good condition. So it's no longer a priority for that maintenance item. I'll do it on this car and see if things change

 

Both of the ones I changed seemed to work fine, too. Dirty, but rattled back & forth just fine. I just replaced them because I was replacing plugs and it was easy & cheap to swap the valve while I was in there. Like I said, I don't know if it made a difference. In fact, I doubt it.

 

Changed the PCV today, took me about 10 minutes with my new early father's day gift (a milwaukee power ratchet), dang it was fast.

But the PCV that was removed had no issues, rattled nicely and was still pretty clean. I was tempted to stick it back in.....but for what it's worth, I put in a new part.

 

Power ratchet!!! Arrrrr! One of these days, I'm gonna spring for one.

 

This power ratchet is great if you like to do diy. Such a big time saver.

Got the idea from reading the recent posts on engine rebuilding, don't know why it took me so long to get one

 

Same here. Plus I have a friend with one and he can fly using that thing.

 

I have a 2004 with 140K miles. I was having a new actuator pump put in...so with everything unbuttoned...decided to put in new pcv valve. See attached photo. Mine still rattled, but was coated inside with layer of grime.... also had throttle plate superficially cleaned. My mpg have always been good, but very good now. HWY ave 50 mpg, city >.

 

Yes that’s the way to do that. Pcv and throttle body clean.

When you replace the pcv remove the 2 hoses that go into the throttle body one of the throttle body inlets will be clogged.
Flush that out with carb cleaner. Look carefully at the hoses ends. Mine were cracked and needed to be replaced.

also lube the throttle body return spring.

Good way to see how your engine likes the oil your running by how much junk is in that TB inlet. This is a very clean running engine if you see a lot of post pcv gunk your using crappy oil.

I run really high end oil you can eat off the valve train it’s so clean.
I have zero gunk in the throttle body,

im lucky down here I was able to bypass the throttle body coolant loop. Car runs really good with a cold throttle body, but you won’t get away with that in Ma though.

 

For oil I always use Castrol high mileage semi-synthetic 5W-30. No problems...burns un-noticeable amount of oil.