i have a 1992 4runner 3.0 and it has been having the worst idle problems.
when started up in the morning it will shake and sound like its missing, it seems that it is running rich, as i can still smell fuel in my exhaust. i changed the plugs to ngk iridiums about 2 months ago and just changed back to v powers last week, this hasn't helped. the truck will run like this for a while then magically it will stop and idle drive perfectly with no power loss like a switch was magically flipped.

 

I’ve had similar situation with my 3.0 as well it’ll run terrible and then like you said it’s like you flip a switch and it runs great for a while and then the problem comes back have you found anything out

 

Sounds to me, for what's that worth, that you might have a cold start injector problem. Either the injector itself, the cold start injector timing switch, or the way the ECU is controlling it. When the CSi system shuts off, all of a sudden, everything is hunky-dory.
You might want to take a look in the FSM for trouble shooting the CSI system.

Another thought I just had, that gave me a headache since I get so few, is the auxiliary air intake valve isn't opening enough to give you the right amount of air to go with the additional fuel the CSI provides. Once again, when the system shuts down, as it should, everything is back to normal, and you're suddenly good to go. Literally
Again, the FSM will guide you on trouble-shooting/repairing it.

I wish you good fortune!
Pat☺

 

If it sounds like it's missing, it probably is. The unburned fuel goes right out the exhaust where you can smell it, but it doesn't mean the intake charge is rich.

So find the missing cylinder. Pull each plug wire, one at a time. The one that makes no difference goes to the cylinder that isn't firing. Put the inductive lead of your timing light on each lead. If the light doesn't flash, that plug isn't firing. (A plug can fire but not ignite the charge; don't confuse the cause and effect.)

You could have a marginally bad plug wire, a sticky valve, or something as simple as mis-set ignition timing. All of these can stop causing a miss (pretty suddenly) with increased engine temperature.

 

i hope the OP has found a solution by now, since the post was made 8 years ago....