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PCV Valve between valve cover and intake manifold

 
Old 12-03-13, 09:57 AM
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McCloudsZJ
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Default PCV Valve between valve cover and intake manifold

Am I correct in assuming there's supposed to be a PCV valve between the valve cover and the intake manifold? The 1992 SC400 I got on Sunday was suffering from (what I assumed was) a pretty serious vacuum leak (among 100 other things). The vacuum line from the intake manifold was just shoved down in the valve cover--there's no grommet or valve or anything.

I grabbed a PCV valve from a pile of parts in the garage and a rubber grommet that kind of fits the valve cover. That seems to have made it better, but... It's obviously not right. What is "right"?

I have over 10,000 posts on other car forums so I know how annoying dumb questions are, but imports are totally foreign to me . I promise no more stupid questions as soon as I find an FSM.

Last edited by McCloudsZJ; 12-03-13 at 10:04 AM.
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Old 12-03-13, 10:10 AM
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one side should have a line going to the intake pipe. the other side you are correct should have a grommet, a pcv, and a line going to the intake manifold. I would get the gormmet, pcv, install the lines and reset the ecu so it can re-learn as it has learned to compensate some for the air leak when its disconnected like that. just pull the battery negative for a minute (10 seconds really).
you can also just drive it around for a while and it will re-learn but it can take a while, and I get better results resetting it before the first cold start of the day so it can learn as the car warms. seems to work best that way.
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Old 12-03-13, 10:26 AM
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Originally Posted by Ali SC3 View Post
one side should have a line going to the intake pipe. the other side you are correct should have a grommet, a pcv, and a line going to the intake manifold. I would get the gormmet, pcv, install the lines and reset the ecu so it can re-learn as it has learned to compensate some for the air leak when its disconnected like that. just pull the battery negative for a minute (10 seconds really).
you can also just drive it around for a while and it will re-learn but it can take a while, and I get better results resetting it before the first cold start of the day so it can learn as the car warms. seems to work best that way.
Cool. Thanks for the confirmation. These engines are a little counter-intuitive, but I didn't think cramming a vacuum hose into the valve cover was right... I found a parts store across town that says they have the grommet and PCV valve in stock. I'll grab those this afternoon and take out the ill-fitting Jeep (I think? I don't really know where it came from) PCV valve.

I'm also getting less than 400CCA from the 5 year old Walmart special of a battery the car came with. I'll get a new battery and put all of it in tonight, then let it relearn tomorrow morning.
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Old 12-03-13, 10:48 AM
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that will probably help out alot, also on another note the walmart special is not that bad, they also have a good return/pro-rate policy... it is walmart after all.
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Old 12-03-13, 12:04 PM
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Originally Posted by Ali SC3 View Post
that will probably help out alot, also on another note the walmart special is not that bad, they also have a good return/pro-rate policy... it is walmart after all.
Advance Auto will give me $20 for it. I'm happy with that. I've always had decent luck with the Autocraft Golds, and for the price and 5 year warrenty, I'll probably keep getting them. I've shelled out $200+ for Optimas only to have them die in six months. Plus, money saved by getting a cheap battery leaves more money for go-fast parts.

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Old 12-03-13, 12:38 PM
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I think my truck has one of those from like early 2000's. somehow still works even when its freezing outside its one magical little battery. don't forget to get the right grommet, you want it to seal so the air pulled through the pcv is coming from the valve covers and not just from the seal area. It pulls the air from the other valve cover breather that has the hose running to the intake pipe, and since that pipe is after the maf, this is all supossed to be measured air, so any leaks at the pcv or even valvecover gaskets (check those 150+k gaskets out they are probably toast) will cause it to draw in unmetered air (like you were doing before), and that usually leads to a rough idle and poor acceleration.
If you see oil coming out of the valvecover gaskets on these cars, you know some air is getting in and its time to change it not just cause of the oil but the air leak it creates.

Also check out lextreme if you are into the v8 modification stuff. alot of good info there as well.
http://www.lextreme.com/pcv.html

Last edited by Ali SC3; 12-03-13 at 12:47 PM.
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Old 12-03-13, 12:59 PM
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I almost always replace the valve cover gaskets and intake manifold gasket within a week of getting a new (used) car. And I'm definitely into modifying V8's. Just never one of these fancy Japanese V8s. I've always run a PCV and catch can on one side, and a breather on the other. This is what I'm used to working on:




I did have a rough idle the when I brought it home on Sunday. It was also running rich as hell. I assumed it was a combination of the ECU learning (no battery in it when I got it), vacuum leaks, and the 89 octane that had been sitting in it for months.

After driving it for a day with the oddball PCV, home made race gas (e-free 93 octane with some Toluene and Xylene thrown in there to get it up around 100 octane), and some Sea Foam, it starts right up and idles wonderfully. It's still a little rich, but not shooting black pillars of smoke out of the tail pipes. I have no idea if it's accelerating as fast as it's supposed to because I have nothing to judge it against. It's slower than both of my Jeeps, but that's not really a fair comparison.

Thanks again for the insight.

Last edited by McCloudsZJ; 12-03-13 at 01:12 PM.
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Old 12-04-13, 06:09 PM
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looks nice, I am guessing its one of the Jeeps. it will take a few drives to learn after a reset, if it doesn't start clearing up it could be the o2's need changing, also some 1uz's just run a bit rich apparently. good luck!
also moving this to the performance/maintenance section.
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Old 12-09-13, 07:19 PM
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So does the guy have a v-8 or JZ?
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Old 12-10-13, 07:47 AM
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says he has a sc400 v8 in the first post.
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Old 12-10-13, 10:04 AM
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Originally Posted by bigwhite View Post
So does the guy have a v-8 or JZ?
Originally Posted by Ali SC3 View Post
says he has a sc400 v8 in the first post.
1992 SC400. 1UZ 4.0L V8. Now complete with a PCV valve and grommet. Thanks again for the info, Ali.

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Old 12-11-13, 09:04 AM
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hows it running now, pick up any power or a little bit smoother?
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Old 12-11-13, 09:39 AM
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It does seem to run better. There's a definite improvement... 95% of the time. The other 5% it's bucking and stalling at 80 mph. If you have any insight into that, I posted a thread called "Gas Cap Question" or something like that.
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Old 12-11-13, 01:03 PM
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sounds better at least, ill take a look at it.
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Old 05-14-19, 03:49 PM
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Default PCV valve

My 2007 gs350 is burning oil very offen, if I replace PCV valve, will that help?
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