Low warm idle in a '91 3VZE, where to start diagnosis? (1 Viewer)

[jfwhite]

I have a '91 pickup that's developed a very low (300-400rpm) idle when warm. It idles where I'd expect when cold: 1700rpm immediately after startup, then 800-900rpm or so for the next couple minutes. I did a basic tune-up after the issue first appeared: plugs, cap, rotor, air filter, the old parts looked fine and the new parts made no difference.

What's odd is that it runs 100% fine other than the low idle. Vacuum appears solid, the engine revs freely through the whole range and is great under load. I'm aware of some of the usual idle suspects with these engines, and I would think that a bum TPS or a clogged IACV would manifest itself in more than just a low idle. I would expect an idle surge, stumble, hesitation.. etc. I know I can bump up the warm idle adjuster or advance the distributor but I would prefer to address whatever is the underlying issue.

I'm guessing my first step is pulling the throttle body to clean it thoroughly? Anything else I should consider testing while it's still in one piece?

Thanks!

 

[KLF]

Did you try adjusting the idle screw on the throttle body?

 

[jfwhite]

Did you try adjusting the idle screw on the throttle body?

That does seem like a good idea.

I can actually still see the factory paint marks on the idle screws so I am fairly confident they have never been touched. I know I could bump them up, but if it was idling correctly before, there must be something that changed, right? Failing VSV, vacuum leak, or sticky IACV, I would guess? Possibly a slight coolant bubble in the TB?

 

[Mudder]

The idle screw it held in place by a rubber O-ring and as time passes it dries out and will allow the idle screw to rotate in and lower the idle or put and raise the idle.

 

[jfwhite]

The idle screw it held in place by a rubber O-ring and as time passes it dries out and will allow the idle screw to rotate in and lower the idle or put and raise the idle.

Thanks, I will definitely take a look! This is the screw directly on top of the TB?

3vze Adjusting Idle -- Help Please - YotaTech Forums

95.5-2004 Tacomas & 96-2002 4Runners - 3vze Adjusting Idle -- Help Please - Oh gurus and members smarter than I (that means most everyone here), I want to adjust the idle on my 91 v6 3vze 4x4, as it seems to be idling extremely low and rough. I read up on the process and using the Idle adjusting...

www.yotatech.com

 

[KLF]

I have also had that O-ring get dried out, and air will sneak past it and mess up the idle. Plus ya the screw will turn on it's own. Adjust the idle then put a piece of electrical tape over it to hold it in place. See if that helps.

 

[old87yota]

You could get a new o-ring and not have to worry about the idle screw backing out.

 

[jfwhite]

I have also had that O-ring get dried out, and air will sneak past it and mess up the idle. Plus ya the screw will turn on it's own. Adjust the idle then put a piece of electrical tape over it to hold it in place. See if that helps.

You could get a new o-ring and not have to worry about the idle screw backing out.

Yep, turns out mine was pretty dry and hard, too. I replaced it and the screw now feels much more tight and snug. I also blasted the TB with about half a can of throttle body cleaner, and the idle now sits at ~650-700rpm when fully warm. It's not quite as high as I'd like but definitely way better than 300rpm. When I have a little more time, I'll pull the whole intake manifold and clean everything more thoroughly... definitely seems like the idle issue is due to general gummie-ness of the throttle body and intake. Thanks for pointing me in the right direction!