lesha30

Hey,

I have 91 4Runner, 3. slow 2WD.
Do you know what regulates the amount of incoming air when the engine is warm?
The problem is that when I drive it for a while, then let it stand for 10-20 minutes and start it back up, the engine is idling rough and on very low rpms. Every once in while the engine even dies because of it. So, my mechanic told me that there is the problem with regulating incoming air when the rig is hot.

Thanx for your responces

lesha30

...and, oh yeah, my mechanic told me that it's not MAF sensor.

Thanks

Firefyter-Emt

TPS ???

lesha30

The TPS has been changed 5K miles ago, although it's adjusted ALMOST perfectly, but the problem still exists.

toy283

The only things that regulate the airflow in the engine (any engine) are the throttle butterflies and thus the throttle peddle. MAF, TPS, O², etc. all regulate fuel flow in accordance for proper burning efficiency.

Unhappy99

I would be of the opinion you are experiencing a fuel problem, not an air problem. How many miles on your vehicle? When was the fuel filter replaced? When were the injectors cleaned? How often do you put injector cleaner in the fuel tank?

rimpainter.com

You have a VFM not a MAF anyway.

lesha30

My truck has 99K miles on it. The last time I've put any injector cleaners in the fuel was 6 month ago. And the fuel filter was changed a year ago (12000 miles).

rimpainter.com

If you give it gas during this condition, does it sputter and idle up?

In other words, does it get smooth as you put your foot in it?

Do you have an Auto or 5spd.?

cubuff4runner

I don't know to much about this but do you possibly have a gas line which got pushed near part of the engine block or other hot spot so it is kinda vapor-locking? It may only get hot enough when it is stopped for a period of time.

lesha30

Yea, when I push the gas pedal just a bit, engine runs smooth. And I have a automatic 4x2

MTL_4runner

Have you cleaned the throttle body?
That will certainly make it idle rough.

lesha30

As far as I understood, T body, if it was the problem, would make the idle to be rough all the time and not just when it's hot and been standing for a while. Am I wrong?

foxtrapper

There are three seperate air passages controlling idle on your engine. One is the butterfly or "throttle" in the throttle body. The second is the idle speed circuit which is a controlled bypass around the throttle. The third is the cold start circuit which is another larger bypass, but this one is controlled by a thermostat. There's a few others, like the a/c circuit that also partially control idle, but we'll leave those alone for now.

When warmed up, the idle air goes through the throttle a little, and through the idle speed circuit. Dirt on the throttle wreaks havoc on the idle speed, particularly when warm, and creates roughness, low idle speed, and stalling. Warm idle speed adjustment is a simple matter of opening up the adjusting screw on the idle bypass. Something your mechanic should have attended to. There is also the distinct possibility that he's screwed around with the main throttle butterfly, which has a very precise setting for idle. If that one is screwed up, you must correct it first.

So, clean your throttle body, check the throttle plate position when closed, and adjust the idle speed correctly on the idle speed circuit. At which point you will probably be fine.

lesha30

Do you guys know how to clean the T. body? I've done a search but came up with nothing.

Thanks

foxtrapper

Carburetor cleaner and a tooth brush. I've a very simple job.