3.0 V6 rough idle

[turtle68]

Hey guys, my new-to-me 1992 4Runner has a rough idle especially while parked or at a stop with the brake pedal pressed. I have installed new spark plugs, wires, and air filter. I am thinking there could be a vacuum leak. Am I on the right track?

The truck runs fine otherwise. Going to the road there is no hesitation or misfire.

 

[giro]

It could always just be older gas or the idle speed set just a little low.

Any reason you didn't do the cap and rotor when doing the plugs and wires? My dad always liked replacing those on new-to-us vehicles....so I guess that means I replaced mine 10 years ago. It's cheap and easy, and is probably time again for mine.

 

[Eacook1]

It could be a vacuum leak. I have a rough idle on mine. Turned out to be low compression on one cylinder. Runs good otherwise.

 

[giro]

BTW, is it an automatic? Mine's a manual, but on other automatic vehicles I've seen the engine speed dip a little when in park....basically the engine working against the brake. Put it in neutral or drive and it goes away.

Likewise with that car putting on the brakes would make the rpms dip a little. I thought someone told me it was due to the high powered brake lights, but I suppose it could be other parts of the brake system.

Either way, it makes sense, and just a small adjustment to the idle should take care of it. It's very easy, and the Factory Service Manual will walk you through it. See the perma-thread about the FSM if you don't have one yet.

 

[91'4bee]

Your on the right path with a vacuum leak. But like the others have said it could be just a low set idle screw, but this is assuming that it is an auto trans(and when in drive). If its a manual trans look for a leak in the line that connects to the brake booster to manifold.

Good luck

 

[turtle68]

Yup, it is an automatic. I'll check out that sticky thread. Thanks!