Car Engine Revving Up and Down How to Diagnose Engine Surge

Hey, everyone. I want to talk to you today about the 3.0. Honda 3.0, that is. We have an '02 Honda Accord in the shop, and it has a surge. What a surge is is basically, the idle's searching. It's going, "Brr, brr." Hope that's a good diagnostic there. It is revving back and forth, back and forth. No check engine light, so you're not gonna have a code that says, "This is the problem," or, "Search in this area." We just know that this system has an IAC valve in it, which IAC stands for idle air control. Kind of makes sense, right? Searching for the correct air-fuel ratio mixture, how much air to let in, and how much air, whether it's hot or cold, whether it needs a lot of air or less air. I'm going to show you a quick diagnostic on this, and alls you need to do is take the airbox off, and I'll show you how to check that IAC valve with just your hand.

So now that we know we have that idle surge searching for the proper idle, I'm gonna show you the location of the IAC valve, and then I'm going to show you how to do a quick test on it. So make sure the obvious, that the airbox line is tight. We don't have a mass airflow sensor in this, so that really won't really affect it, but you wanna make sure you don't have any obvious vacuum leaks. A big vacuum hose that goes to the brake booster, and all the little vent lines are down around the other side. I've already checked that, but the first thing that I can check that is real simple without a scanner is just take the airbox off.

So with that, you need the pliers, 8-millimeter socket, and a Phillips screwdriver. So we're going to take the vent hoses off of the air tube that goes to the airbox from the throttle body. Phillips screwdriver and an 8-millimeter socket. It's gonna loosen up the air cleaner housing. So once you have all the airbox housing bolts undone, we'll just lift it up...there we go...and disconnect it from here. Set that aside. There's another hose back here. Take that one off.

So the IAC valve is located and mounted underneath the actual throttle body to the upper intake. And this connector right here is it right here. This is what a new IAC valve looks like. So you have your connector, little, little module, and inside there, this is the air intake. And what happens is, there's a little damper valve in there that spins, and it opens and closes, and it flexes, almost like your old butterfly on your throttle body, and lets air in and out, all depending on the temperature of the engine.

So this gets carbon buildup in there, and then it'll start to not seep all the way. So you'll get too much air, and the car will be like, "Well, where do you want me to go?" And it just does a constant searching, which is a search for the air. So, to test this, we can run this with this airbox cover off because, once again, there is no mass airflow sensor. So I'm gonna start her up, and I'll show you how to see if the valve is no good. Okay. So now, we're at this point where the car is doing its surge. You're going to take your hand, and you'll see a port right here. See that wad of air? You're going to take your fingers and bring it right over the top of that, and if the idle smooths out, that IAC valve is stuck wide open. And that's a quick diagnostic, and we're gonna do it without any scanners.

So hopefully, you enjoyed this video and it helped you out. If you had not already subscribed, please subscribe. Ring that bell, and turn on all your notifications. Until next time, be safe.