VTV confirmation

[jfnall]

Been going through my 10 year old desmog. Needing to get clarification on the VTV on the carb that connects to the Choke Breaker. Some pics show the green side to the front and the diagram shows the green side to the firewall. Who’s right? Both pics were “Jim c rebuilds” according to the posts. Thanks

 

[4Cruisers]

Green side towards the firewall.

 

[SHFTY60]

Just to utilize the search functionality, I’m going to post a question about VTV’s here…

I was replacing all vacuum hoses today and I successfully pulled off hoses on all VTV’s except one. Unfortunately, I do not see it referenced in the emissions manual. I also don’t find it online when searching for a black/white VTV. Here’s pictures of the busted piece as well as the manual with a markup of where it was located in my rig. Questions are: 1) if manual doesn’t have it, do I need to concern myself with replacing? 2) If I should replace, any idea on what to search or where to search to find a replacement?

 

[OSS]

That's an EGR valve hack and not part of the original system.
The idea behind it is for the VTV to slow the EGR valve opening by restricting the air flow to help prevent EGR hesitation at light throttle acceleration.
In some sense it does do that, but it can have an unpleasant side effect when the throttle is released.
Those VTVs restrict air going one way to slow the actuation of whatever and don't restrict (much) air flowing the other way.
The key word here is "much". There's still some restriction flowing through the free flow direction which can cause an old EGR valve to stick open because the difference in vacuum pulling on the valve vs letting go wasn't abrupt enough to set the diaphragm free.

You can use that VTV if you want and also try driving without it. It's up to you whether you think it's an improvement or not.
If you can't tell the difference either way — get rid of it.

Whatever you do — don't install it backwards!

 

[SHFTY60]

Thanks @OSS. I am in the process of preparing for a (CA) smog test. Rebuilt the carb and plan to finish the hoses and then take it in to see where I stand. I think for now I’ll just hook this up without the VTV. If I fail, perhaps that’s one (of most likely many) thing I can try to pass.

 

[DFXR]

OSS is correct as usual - I have a black and white Vacuum Delay Valve in that same spot, as an EGR hack. Without it, I get enough of the classic stumble at low RPMs that holding a steady 15/25mph on the dyno is very difficult for a smog tech.

I recently passed CA smog with the VDV in place. The black/white ones open (roughly) between 4-8 seconds after getting a vacuum signal. That’s enough to smooth out the low RPM performance but still allow the EGR to operate at higher RPMs and cut the NOx. General driveability is of course better. I don’t notice anything weird on decel.

See how she runs without it and then go from there.

 

[DFXR]

If you end up wanting to replace it, here’s some more detail (post #212):

The Classic FJ60 "Stumbling/Hesitating Acceleration/Running Problem

forum.ih8mud.com

 

[SHFTY60]

Thank you @DFXR

I went ahead and ordered the one you posted about. I'd imagine smog issues happened with a previous owner and this was added to get it to pass. I will drive it around without, just to see, but assuming I get everything put back together, I'll install it to go in for my test.

 

[OSS]

Technically- adding that VTV to the EGR vacuum hose is considered tampering. By the book, it's illegal to do so. Most techs probably won't care though

 

[4Cruisers]

Technically- adding that VTV to the EGR vacuum hose is considered tampering. By the book, it's illegal to do so. Most techs probably won't care though

How thoroughly do they do the visual inspection? I would think they'd look for missing components, not extra components. Would they even notice?

 

[SHFTY60]

Thanks @OSS, will keep that in mind.

 

[OSS]

A long time ago I took my cruiser to a random smog shop and it had one extra vacuum switching valve (VSV) that I had installed extra for something else bolted to the fender with a dangling vacuum hose on it. It wasn't part of any smog equipment but it was identical to other VSVs that were.

When the tech saw that VSV with the loose hose, he got all agitated and refused to test my vehicle - going on & on about this or that.
Other shops don't care. Just gotta find a friendly one .

 

[SHFTY60]

I'm assuming the shop I've gone to is friendly... they passed me last time WITHOUT the air intake hose . They did suggest I "work on that before you come back"

 

[DFXR]

I think it really depends on the shop, the tech, the time of the day, the time of the month... meaning of course that nothing is for sure. Some of the shops might really care about tampering but many others are just worried about getting popped in some kind of sting operation.

But a black/white VDV in that spot looks fairly normal. On the other hand, a black/yellow (the next step up for delay) kinda jumps out.

The fact that you have tested in this place before and they can assume you’re not a narc will probably help.