PCV issues

1989 c1500 5.7 tbi
I’m fighting a high idle issue and I’ve sprayed carb cleaner all around the intake manifold, throttle body gasket, and all hoses under vacuum. I think the culprit is my PCV valve. I have a new one installed and it’s functioning properly. The stock hose has no leaks but at idle the right angle portion that connects to the throttle body collapses completely and partially pulls my pcv valve out of the cover. Would that cause an idle issue? Also is the PCV valve supposed to have a gasket between it and the valve cover? Thanks for any help you can give.

brinx182 said:

1989 c1500 5.7 tbi
I’m fighting a high idle issue and I’ve sprayed carb cleaner all around the intake manifold, throttle body gasket, and all hoses under vacuum. I think the culprit is my PCV valve. I have a new one installed and it’s functioning properly. The stock hose has no leaks but at idle the right angle portion that connects to the throttle body collapses completely and partially pulls my pcv valve out of the cover. Would that cause an idle issue? Also is the PCV valve supposed to have a gasket between it and the valve cover? Thanks for any help you can give.

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It would cause it to run lean, especially at low rpms. Stands to reason more air = lean condition = more fuel sent from ECM = high idle. Even if that ain't the problem, it's a problem, and a cheap and easy one to fix. Auto zone has the PCV hose couplers available and they're so cheap, i don't remember how much they cost. $5 even sounds high to me.

Normally I'm a pretty big fan of looking at the data, but I think you can wait until after you fix the obvious problem before you look at the data here. The only thing you're going to do is confirm there's a vacuum leak until you get it fixed. After you've replaced the boot, attach vacuum gage and make sure that's the only issue.

On my 1997, I don't recall a gasket between head covers and PCV, not sure how it is on TBI

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RawbDidIt said:

On my 1997, I don't recall a gasket between head covers and PCV, not sure how it is on TBI

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TBIs have a "D" shaped rubber grommet in the valve cover in which the PCV valve goes, on the passenger side. On the driver's side there's another grommet that has a tube which goes to the TB spacer to vent the crankcase too. The PVC is hooked to the bottom center plate of the TB and gets engine vacuum. The other vent tube is at atmospheric pressure since it's above the throttle blades of the TB. Older engines just used a vented air filter but, TBIs sucked it back into the intake to reduce emissions. You need to have both to properly breathe.

PlayingWithTBI said:

TBIs have a "D" shaped rubber grommet in the valve cover in which the PCV valve goes, on the passenger side. On the driver's side there's another grommet that has a tube which goes to the TB spacer to vent the crankcase too. The PVC is hooked to the bottom center plate of the TB and gets engine vacuum. The other vent tube is at atmospheric pressure since it's above the throttle blades of the TB. Older engines just used a vented air filter but, TBIs sucked it back into the intake to reduce emissions. You need to have both to properly breathe.

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Good to know, thanks.

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Guess I'll hijack here since my 93 tbi pcv setup is

PlayingWithTBI said:

TBIs have a "D" shaped rubber grommet in the valve cover in which the PCV valve goes, on the passenger side. On the driver's side there's another grommet that has a tube which goes to the TB spacer to vent the crankcase too. The PVC is hooked to the bottom center plate of the TB and gets engine vacuum. The other vent tube is at atmospheric pressure since it's above the throttle blades of the TB. Older engines just used a vented air filter but, TBIs sucked it back into the intake to reduce emissions. You need to have both to properly breathe.

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I keep wondering since my motor was replaced with a crate engine with a roller cam and is basically unknown beyond that, if there's any chance just using the stock replacement pcv valve for the original motor isn't the best?
Reading around about vacuum and valve specs..etc seems to point to there being some kind of way to dial in the correct pcv valve?
Anything to waste time thinking about?
Are there any methods or tests to find out if things are working as they should?

scott2093 said:

Reading around about vacuum and valve specs..etc seems to point to there being some kind of way to dial in the correct pcv valve?

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I'm running this with no issues.
www.gmpartsgiant.com/parts/gm-pcv-valve-6487779.html

PlayingWithTBI said:

I'm running this with no issues.
www.gmpartsgiant.com/parts/gm-pcv-valve-6487779.html

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Thanks. That's what I'm running and shows up for my truck. Well whatever the AC Delco version is ...
Guess that covers a lot of years which would include the different cams ft vs hr....

scott2093 said:

Guess that covers a lot of years which would include the different cams ft vs hr....

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I've been running the same one through 3 different cams - 208/213 @ 0.050, 224/224 on a 350 and a 230/236 on a 383 - worked for them all.

You had to ask if a collapsing hose at the TBI is bad? If it collapses it is bad and may even be leaking vacuum there. Yes, as has been said, there is a D shaped rubber grommet for the PCV valve to slide in to. Never has had a gasket.