1997 4runner, 3.4l: idle speed too low, engine stalls at idle

[werminghausen]

My idle speed falls to around 500-550 rpm when hot.
It happened now several times that the engine stalls at a stop light.
Is there a safe way to raise the idle speed to 600-650?

Best, Martin

 

[dhalsey]

I have had three vehicles with 5vz-fe's. My first two when I was younger were tacomas. I actually got rid of the first one because of this same problem. There was nothing wrong with the idle. It was always the fuel system being dirty. Using poor fuel quality or mixing multiple brands of gas that are of poor fuel quality is your issue. I spoke to a retired engineer that worked at a fuel refinery in ca. He said that the additives that are used in modern gasoline can sometime conflict with other additives of other brands. You need to search for the how to seafoam your truck. Or try lucus fuel additive every other tank and just drive it clean.

 

[zumogo]

IMHO there are a couple of things that might be looked up or change. Fuel filter, 02 sensor MAF sensor air filter etc

 

[baja1]

My idle speed falls to around 500-550 rpm when hot.
It happened now several times that the engine stalls at a stop light.
Is there a safe way to raise the idle speed to 600-650?

Best, Martin

hey my '97 that has been running deadnuts perfect did that to me for the first time a few days ago! coming off the freeway down the offramp engine died at the stop. I was thinking maybe the IAC? I cleaned the TB but not the IAC, gonna give that a try. anyone know if there's anything in there that would be harmed by a soak in chemtool carburetor cleaner???

 

[nissanh]

Mine is around 550-600 and works great. How old is your transmission fluid?

baja1: when you clean the TB, the dirt falls right into the IAC, clogging it. The best way to clean TB is to remove it off the engine and have the IAC at 12 O' clock and clean. If you plan to clean IAC, then remove it and clean and put a new gasket between TB and IAC and install. If possible get a new gasket for the Tb ad intake manifold.

 

[werminghausen]

Mine is around 550-600 and works great. How old is your transmission fluid?

Hey, my transmission fluid might be very old indeed. Do you think fresh fluid will be less restrictive and therefore the engine idle speed is reduced less when at a stop? Any way a good idea to change the trans fluid.

Adjusting the Idle Air Valve (is this the IAC?): Is there a way to adjust this unit inside to give the engine a little bit more air (and rpm) at idle?

fuel filter: good idea to change this one... anyhow.

fuel additives (Lucas fuel additive or sea foam) : not sure if this will cure anything?

Best, Martin

 

[nissanh]

Do a drain and fill. You can find the fluid type on the dipstick or on the drain bolt. Buy from the dealer. You'll drain about 4 quarts and will need exactly 4 quarts to fill it right.

There are two types of trans fluid at the dealer. The old version is what went to my 97 and is about $10 a quart. New version called T-4 is about $6 and does not include my fluid type.

 

[werminghausen]

Drain Transmission fluid:

Are you saying skip the filter and just use new fluid?
Makes things much easier of course.
I have Transmission fluid on the shelf: Toyota ATF Type T -IV
Is this the correct fluid?

Martin

 

[werminghausen]

How about sea foam vs BG 44K? I have that stuff on my shelf at least. What is the difference?

Martin

 

[Park]

I have this problem too. Its intermittent but it never occurs unless I'm running 87oct. I usually run EO87, and dont have the idle issue. Im planning on changing out the fuel filter and installing some new NGK plugs. Hopefully that cures it.

 

[gamefreakgc]

Uhh... changing the transmission fluid isn't going to make a difference. The transmission isn't under any stress at idle...

It's your IAC (Idle Air Control) valve. Take off the throttle body (get a new gasket) and you'll find it on the underside. Take off the IAC and inspect (also need a new gasket for the IAC). While you have it off, clean the throttle body out really good with a rag.

With the IAC off, Inspect the valve itself as well as the coolant passages inside. Are they corroded or clogged? New IAC is in order. Coolant passages clean but the valve itself is dirty or clogged? Try cleaning it with a q-tip or something like that. You could try cleaning it with MAF or carb cleaner, but not sure if that'll help.

Put it all back together and stalling should stop. That's assuming your spark plugs are wires are good.

 

[baja1]

hmmm....I thought a similar problem was caused by a dirty IAC after cleaning the TB and thinking some crud had fallen in there. took it apart today and found it surprising clean, soaked it in chemtool with the plastic electronics not submerged, put it all back together and still runs great. pretty sure that wasn't the culprit!.......:juggle: