Question about 1990 Toyota 4Runner
Have you looked at your idle air control valve
What is it? This is an electrically driven valve that allows additional
control over the throttle at idle
Where is it located? The IAC is located on or adjacent to
the throttle body and consists of a small device held on by two bolts with an
How does it work? When the throttle is closed the throttle plate closes off any air from the intake manifold. In order to stop the engine from stalling due to lack of air the IAC opens a small valve allowing air to pass from the air ducting to the intake manifold. Often the IAC components consist of an air inlet port in the inside wall of the throttle body, immediately in front of the throttle plate, with a similar exit port behind the throttle plate. Connecting the two ports is a motor driven valve. When the valve is opened air effectively by-passes the closed throttle plate to maintain the engine at idle. The IAC also augments the throttle when additional power demands are put on the engine such as steering.
Symptoms of faulty IAC
How to check? Physically remove the IAC but keep the electrical connection to it. Temporarily block off the now open ports on the throttle, turn the engine on and examine the IAC valve action in response to additional loads (power steering inputs etc). The valve should open and close according to demand.
How to fix? If the motor of the IAC has failed then replace the IAC. If the valve is gummed closed by baked oil and carbon then clean it thoroughly with carburetor choke cleaner spray and a cloth. Similarly if the entry and exit ports on the throttle body to the IAC look blocked again clean them out thoroughly.
Posted on Jun 03, 2010
Testimonial: "Fast response and good advice, I'll try these suggestions and let you know the results."
Leaky vacuum hose, faulty idle air control valve, can affect the idle bad 02 sensors can make it to rich or lean, in your case too lean. A dirty throttle body can plug up the sensors as well.
Posted on Jun 03, 2010
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
Tips for a great answer:
Jan 18, 2014 | 2008 Toyota Corolla
Apr 10, 2013 | Cars & Trucks
Mar 02, 2012 | 1991 Toyota Pickup
Sep 17, 2011 | 2001 GMC Jimmy
Apr 18, 2011 | Chevrolet Cavalier Cars & Trucks
Feb 18, 2010 | 1993 Lincoln Mark VIII
Jan 14, 2009 | 1994 Nissan Altima
Dec 03, 2008 | 1999 Ford Taurus
Nov 13, 2008 | 2002 Chevrolet S-10
1,804 people viewed this question
Usually answered in minutes!
Step 2: Please assign your manual to a product: