'73 PCV valve leak, High idle even after throttle body rebuild Options

[chmillman]

Hi all,

So still working on the FI, have gotten a lot of stuff fixed. But, despite rebuilding the throttle body to fix an air leak around the worn shaft, the idle is still too high even with the screw turned all the way in. My FI guy did some research and found that the PCV valve is leaking. He put a constrictor clamp on the hose from the PCV valve to the intake manifold and adjusting that brought the idle down.

Apparently the configuration on the '73-'74 motors was to route the output hose of the PCV valve directly to the intiake manifold, whereas before/after the hose just went to the air cleaner. So if there is a leak in the system, it can cause idle problems - I guess that's why they changed it...?

Anyway I found this 5 year old thread here:

http://www.914world.com/bbs2/index.php?sho...c=347986&hl

Again apparently, since the original PCV valve is NLA, there was a suggestion that it be replaced with a Toyota part - haven't checked if it is still available. Is that still the current thinking? Having read the thread, I am a bit worried about the potential overpressure/underpressure problems it could cause...

Other possibility I guess would be to eliminate the PCV valve entirely and pipe the hose from the oil filler neck directly back to the air cleaner, and plug original hose entry into the intake manifold ?

Any other suggestions? TIA!

[emerygt350]

The active pcv (what?) is actually pretty clever. It should be causing a slight increase in your idle. That is the way it was designed. Even at idle it is drawing gasses off of your crank and heads. That is part of the problem with after market, that idle bleed needs to be a specific volume. Anyone with an active pcv will notice an idle drop if you plug it. It is a dead simple device. Pull it, clean it, put it back in. If you plug it and your idle drops from (what? Have you told us what your idle is now?) to 750 or so, you know it is all the pcv. If you plug it and your idle drops to 900-950 something else is causing the high idle.

Even with a perfect motor, a rich mix and/or timing, particularly timing, is going to cause a high idle. Remind me, 123ignition or stock? Are you certain your retard/advance is setup correctly if it's stock? Are your weights sticking?

Put a timing light on it and see what kind of advance it has at idle (with everything connected).

[Lockwodo]

I installed a FRAM FV279 PCV valve in my '74 2.0 a few years back, no kicks or complaints.

[emerygt350]

I installed a FRAM FV279 PCV valve in my '74 2.0 a few years back, no kicks or complaints.

was that plug and play or did you have to mess with it?

[Ishley]

I did the Toyota PCV valve and it works well. I ordered several so I have backups. like $5 here in the US.

[Lockwodo]

I installed a FRAM FV279 PCV valve in my '74 2.0 a few years back, no kicks or complaints.

was that plug and play or did you have to mess with it?

Direct fit. I replaced the PCV valve and the grommet at the same time.

[emerygt350]

I installed a FRAM FV279 PCV valve in my '74 2.0 a few years back, no kicks or complaints.

was that plug and play or did you have to mess with it?

Direct fit. I replaced the PCV valve and the grommet at the same time.

Where did the grommet come from?

[Ishley]

Amazon for the grommet.

[emerygt350]

No modifications needed?

[Lockwodo]

A direct replacement, no mods needed.

[emerygt350]

Interesting! I might give it a go and see what happens...

[JamesM]

IF you go the route of open venting the crank case to the air filter there are a few other things you should do as well.

First PLUG THE HEAD VENTS!

Second, get the later style (75) larger oil tower vent.

The number of cars I have seen with improper crank case venting setups at this point is mind boggling. The vented heads sort of work alright when there is vacuum on the crankcase but take away the vacuum and don't increase the vent size, the crankcase starts venting pressure (and liquid oil) out the head ports. At sustained high rpm this is bad enough to vacate the sump and starve your oil pickup!