Usually a faulty idle control valve will produce symptoms noticeable enough that the driver will quickly become aware that there is an issue. If your vehicle is experiencing any of the symptoms above, or you suspect that your idle control valve may be having a problem, have the vehicle diagnosed by a professional technician to determine if the idle control valve needs replacement. This article originally appeared on YourMechanic. Autoblog is partnering with YourMechanic to bring many of the repair and maintenance services you need right to you.
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If you'd be so kind as to allow our site, we promise to keep bringing you great content. Thanks for that. And thanks for reading Autoblog. Irregular idle speed One of the most common symptoms associated with a problematic idle air control valve is irregular idle speed. Check Engine Light comes on Another symptom of a potential issue with the idle control valve is an illuminated Check Engine Light. It has a sensor and electrical wires attached to it.
Check the owner's manual for the exact location. Unscrew the idle air control valve by removing the screws that hold it to the throttle body. Detach any wires coming from the valve so you can remove it completely.
Clean the valve by soaking it in gasoline. Move the flap in the valve while it's soaking, to ensure the gasoline reaches inside it. Drain off the gasoline. Dry the valve well by blowing compressed air into it. Check that the flap moves easily. Replace the idle air control valve, reattaching it with the screws and reconnecting all wires [source: Berenis ]. An idle air control IAC valve is a mechanical device that controls the amount of air entering the throttle plate in fuel injection-based vehicles.
A normal healthy idle air control valve will provide smooth idling in your vehicle. But if the valve goes bad for any reason, the idling will go from smooth to rough. A rough idle will result in intense vibrations forming whenever your vehicle is stopped with the engine running. Since less air will be going into the engine during its idle state, the car will react by shaking profusely. As soon as you start your car, the idle air control valve will immediately malfunction.
If you happen to be away from home and this happens, the stalling will happen every couple of minutes in the beginning. You should be able to make it to the nearest mechanic in time before the engine stalls completely.
Sometimes the engine stalling will happen on its own while other times, increasing the load on the engine will cause it to stall. For example, if you turn on your heater or air conditioner when you have a bad idle air control valve, then your engine will probably stall immediately afterward. To temporarily fix this problem, just turn off your heater or air conditioner to reduce the load. Then let the engine cool for a couple of minutes.
If a voltmeter shows a reading outside of the normal range, then you need to purchase a new idle air control valve. Of course, the labor cost really depends on the hourly rate of the mechanic.
It is located on bottom side of the throttle body, and easiest to adjust if the throttle body is taken off. Has hex head, tighten to increase idle and loosen to reduce idle speed. I feel turning around 1. I removed it to see if is sticking but it seems fine.
Could the electrical conection been the reaskn for this. Iac bad wheh car is put into reverse or drive an car wants to die when in park or drive if warmed up doesnt die. Could a bad transmission cause your cars rpm needle go crazy when idling I drive a Cadillac Seville.
I,m being told that is the problem. Any ideas welcome. Hi Carol, I would get a second opinion from another mechanic. If your transmission is behaving fine no jerking, engine speed matches ground speed, etc you could simply have a bad tach sensor or instrument cluster.
Take off your egr valve, emission gas regulator, if it is clogged up and the cars vacuum cant actuate the diaphragm inside it, it will cause the rough sporadic idle you describe and ultimately effect the transmission, by leading to a clogged catalytic converter, that causes extreme loss in power as the vehicle cant release the exhaust causing back pressure.
If you are not racing the transmission not slamming it into park drive reverse i highly doubt it is the transmission. A bad transmission issue would be shift solenoids or maybe cracked torque converter, that would just cause the engine to stall immediately as you put it into reverse or drive if you are in park or neutral and still having idle issues it is not transmission related as the motor is not engaged to the transmission.
If driving performance improves you have clogged cats, depending on the car you may have up to 3 example, a v6 or v8 has 2 exhaust headers therefore 2 upstream cats and 1 downstream unless you have dual exhaust then you have 4, 2 upstream and 2 downstream on a 4 cylinder motor has 2, 1 up and 1 down, catalytic converters are not cheap and most often require a muffler shop to install new ones. Simple test take an old rag and cup the tail pipe if it blows your hand off after a few seconds you cats are functioning properly if not odds are one or both are clogged.
My bet is on that pesky EGR valve. The only other thing i can think of that would cause a sporadic idle is the Idle Air control valve, this one is activated by electronic solenoid that is governed by your vehicles temperature sending unit these two components work in conjunction with the throttle position sensor ignition timing etc.
The IAC can be checked with a volt meter you would have to look up your vehicles operating parameters and use the volt meter to check for abnormal readings, good indication of bad IAC. On many applications, the spec calls for 7. If it is out of specs, the ISC solenoid is bad. Also check for shorts between both ISC solenoid terminals and the case.
Voltage should also vary when the engine is running. No voltage indicates a wiring or computer problem. The AIS driver circuit can be checked with a bi-directional scan tool using commands to increase idle speed.
No change in commanded idle speed would tell you there is a problem in the driver circuit, the wiring or the solenoid. You can remove the AIS from the throttle body to see if the valve pintle is moving in and out, or simply listen for the motor to buzz.
In the engine running test mode 70, which checks the throttle body minimum air flow, depressing and holding the proper button on a hand held scan tool should close the AIS bypass circuit. At the same time, ignition timing and fuel mixture are fixed.
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