My car hasn't ever idled to smooth, it tends to bounce up and down when the motor is cold. I read a thread about cleaning the IAC valve screen so I decided to do so. It made a world of difference, my idle is a lot smoother, and gradually drops when it gets warm, doesn't bounce up and down like it used to. If your car idles like poo you might want to clean yours, it doesn't take much time.
1. Locate the IAC valve, it is in the middle of the IM and has a grey connector going to it. It is in the orange box in the pic.
2. Disconnect the grey connector. Remove the upper bolt with a 12mm socket. You may be able to use the 12mm socket on the lower bolt, but I had to use a 12mm box wrench. Finesse the bolts out and set them aside, try not to confuse which bolt goes where (one is longer).
3. Grab your pliers and move the clamps that hold both of the hoses on the IAC valve. Grab a rag and keep it near, as you might lose a few drops of antifreeze. It may take a little work to get the hoses off; sometimes it works best to take a small screwdriver and insert it into the top to stretch the hose out a little.
4. Spray some carb cleaner on the screen to break up and carbon up. As you can see my screen wasn't bad, but had enough buildup to have an unsteady idle.
5. Connect both hoses at the bottom of the IAC valve, bolt the valve up to the IM and then connect the grey connector. Your car should idle a lot better if there was much buildup on the screen.
Originally posted by 98TypeSH Very nice write up, I will have to try this maybe it will help with my rough idle problems. About how much antifreeze do you lose?
FAQ this.
just a few drops, but antifreeze is messy so you might want to clean it up.
If you're using carb cleaner make you you clean it out throughly since it will eat away the rubber seals. I'm not sure what the internals of the IAC are sealed by, but I'd clean it out throughly before reinstalling it. Also, while doing this make sure that if your gasket is pancaked, go buy a new one.
when doing mine I removed the little rubber gasket, if you do this be careful. when I put the gasket back in it stuck out some, so I'm not worried about any leaks. as for the car cleaner, it is a good idea to not use a whole lot. The carb cleaner breaks up the carbon pretty fast, so you don't need to douche it. As for what is inside I think there is a spring of some sorts, but I didn't mess around with it much.
You might be able to use electrical cleaner as well. Ive used it to clean the heated wires on a MAF sensor once, and it still works. BTW, if you ever work on a car and think something is wrong with the MAF sensor (readings off, MAF sensor related codes), take it apart and spray the wires off, it might fix the problem. Anyway, I think Im going to take mine off and give it a look. If its dirty, Ill try the electrical cleaner and let you guys know how it works.
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2001 Prelude Base (#173 DSP)
Electron Blue Pearl
A lot of go faster, turn harder parts.
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I cleaned mine when i was attempting to take off my intake manifold, and it had a surprising amount of carbon buildup; though not enough to cause a messed up idle
I did this last night. It took all of 20 minutes at the most. He is right, there is not much room for a socket, but fortunately I had a new set of wrenches I got with a gift cert. Mine wasn't very dirty even with 96k miles, but I cleaned it with some nitro cleaner and it seems to run a little more smoothly.
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97 EGP Base 5spd Prelude. Engine: DC short ram, DC SS headers, AEM pulleys, Random High flow cat, Mugen sport exhaust, Apexi VAFC. Suspension: Tein SS, Tanabe front lower tie, Neuspeed front upper strut, Neuspeed rear sway, Tanabe rear upper strut, DC rear lower tie, 17X7.5 5Zigen Typhoons with 215/40/17 Goodyear F1 GS-D3s. Other: Bride Ergo II, Spoon oil cap, Magnecor wires, relocated Odyssey 680 battery, Denso iridiums, Mugen pedals, Mugen lugnuts, shortened shifter w/ Momo airleather, Rotora slotted rotors and Endless NA-Y pads, Goodridge SS lines.
carb cleaner will get rid of carbon buildup best, but it can be harsh on rubbers/plastics. I'm not sure what is inside the IAC valve, I never took mine apart. I used Pyroil carb and choke cleaner. You could do what Ben did but soak the swab with carb cleaner, that would keep whatever is inside the valve safe too. Any auto store will have carb cleaner as well as brake/electrical cleaner, so don't wory where to find it.
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