Engines with electronic throttle body control can use the throttle body motor to modulate engine idle speed, operating autonomously until the driver steps on the accelerator. Photo courtesy of Flickr. Know How. Ben has been taking things apart since he was 5, and putting them back together again since he was 8. Now, he writes on automotive topics across the web and around the world, including new automotive technology, transportation legislation, emissions, fuel economy and auto repair. Your email address will not be published.
Save my name, email, and website in this browser for the next time I comment. Categories Know How Tags auxiliary air control , IAC , IAC valve , idle air control , idle air control motor , idle air control valve , throttle body , throttle plates.
Resulting in fluctuating idle when cold. I assume it went away after water heated up to not be trying to pull water from the reservoir. Who would have thought….. I have a pontiac G5 and the rpm needle junps up and down when driving usually between Any ideas?
This could be an electrical issue with the gauge cluster. Cleaning any electrical contacts related to the tachometer signal may help, or you may have to swap the cluster entirely.
A multimeter may help you test to ensure your connections are good. Some vehicles get their tachometer signal directly from the ignition coils. If an ignition coil has a dirty signal firing when more often than it should be , it could overheat and fail completely. Since ignition coils can be spendy, I suggest you check a wiring diagram for your vehicle to see if the tach is driven from the ignition coil as it is on one of my cars. On these types of systems, there is usually one wire that is a dedicated tach signal.
You may have a power, ground, trigger wire, and tach signal. If your tach works this way, then figure out if the ignition coil is the root cause or if the bad connection is limited to the cluster. A repair manual should have this diagram. If this is all a bit confusing, it might be best to bring it by a shop and describe the issue in as much detail as possible and have them deal with it.
I have been struggling with my v6 Ford Explorer Sport Trac … at idle it misfires 3, 2, and 1 … the other side is completely ok. It accelerates fine most of the time but when I give it the gas to quick from a dead stop sometimes it goes into limp mode for a block or so then all of a sudden it run good… still rough idle due to the misfires.
I have replaced the plugs, wires, ignition coil 6 pack, had the fuel system cleaned, and replaced the fuel pump. I cleaned the map sensor, and all the sensors I could find and at least one other mechanic cleaned them also.
I even tried running premium gas in it. If I am out on the it runs like a champ at km or even km… I feel like a squirrel chasing my tail. Start with any part you have two of — one for each bank. It might help to take a look at a factory service manual or repair manual to see which parts could cause a whole bank to misfire. Hi I have a Mitsubishi eclipse Spyder and I took it to a shop where they told me the code is reading po the idle air control valve.
I was just wondering if that would cause it to be jerking when it goes into 3rd gear. It is an automatic with the option to use the sport control. Thank you in advance. And have a great day. Any advice would be great and much appreciated! The issue you describe sounds like a vacuum leak or idle air control valve. I really appreciate it! The TBI unit. Up to hp engines that air flow is fine. You can drill a hole in the base to put your IAT sensor in.
Also toss the choke collar that is between the TBI and the air cleaner assembly. Good for around 5hp on a car and again mandatory for any decent engine upgrade. That is why I took the negative off and turned the truck on and every time I connect the battery the valve would move then. But not when I just turned it on with key.
It should not move when you turn the ignition switch on. You just confirmed that. If you tug really hard, you can pull the pintle valve out of the IAC motor. Install it that way, then if idle speed is too high when you start the engine, it has to be due to a vacuum leak.
You may need a smoke machine to locate that, but a leak that big should be easy to find by pinching off various vacuum hoses. The computer will not retract the valve unless it needs a higher idle speed You are going to have to use a scanner to see what the engine computer is trying to do. That will also let you see all the other sensor readings the computer is responding to.
Most scanners will have an IAC test that allows you to raise engine speed in rpm increments up to rpm. If that changes engine speed, the IAC is working properly. Also, remember that just driving the truck will not initiate a relearn of minimum throttle. You have to coast for at least seven seconds. The computer needs to see sustained unusually high manifold vacuum to know when to take a reading from the throttle position sensor and put it in memory.
And if you disconnect a battery cable again, then reconnect it, minimum throttle will be lost from memory, and engine speed will be too low.
If it is too high, it cannot be due to the IAC position because that entire circuit will not be working yet. Thanks so much. I have one last question, I have two bolts broke off my exhaust manifold would that cause any symptoms I am having?
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