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IAC valve issues.

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Old 07-21-2008   #1 (permalink)
Cleft_Asunder
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IAC valve issues.

I installed a new throttle body gasket recently. I removed the IAC valve to clean the throttle body. I retorqued everything to Honda shop manual specs. The engine light has come on twice for intake air control, the second time after I cleared the code. Rechecked everything, it's all good. The IAC valve stems are corroded due to the previous owner running water through the car. Car worked fine for 100 miles after I double checked (re-tightened) everything.

After the light comes on, the car has a tendancy to idle at high RPM. It dies down after 6-10 seconds. I'm guessing to about 1500rpm. When I depress the gas a little bit, it goes into a zone where the engine is shacking back and forth as if it's VERY LOW in rpm. So we have high RPM on one hand, but when the gas is pressed I'm getting low RPM in relation to pedal depression. When I drive the car, the RPM's feel really low. If I turn off the car while coasting, and then turn it back on, the problem goes away every time.

I have been having coolant issues for a while now. I know there is a leak I can't fix in at least one hose. The resevoir tank isn't oscilating up and down in relation to hot/cold engine heat. It just stays flat. Could this be the problem?
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Old 07-21-2008   #2 (permalink)
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Re: IAC valve issues.

you must reset the ecu and do idle learn especially after removing the TB. it will throw the idle way off. if that doesnt fix it, you need a new throttle body assembly usually $50 on ebay, make sure its manual/auto based on your car.
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Old 07-22-2008   #3 (permalink)
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Re: IAC valve issues.

Quote:
Originally Posted by gearbox View Post
you must reset the ecu and do idle learn especially after removing the TB. it will throw the idle way off. if that doesnt fix it, you need a new throttle body assembly usually $50 on ebay, make sure its manual/auto based on your car.
I will try it thanks!
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Old 07-22-2008   #4 (permalink)
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Re: IAC valve issues.

Quote:
Originally Posted by gearbox View Post
you must reset the ecu and do idle learn especially after removing the TB. it will throw the idle way off. if that doesnt fix it, you need a new throttle body assembly usually $50 on ebay, make sure its manual/auto based on your car.
I know how to do an ECU reset, but not an idle learn. Can't find consistant info on it.
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Old 07-22-2008   #5 (permalink)
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Re: IAC valve issues.

Oh yeah, I forgot to mention that I accidentily tore my new OEM intake manifold (not TB) gasket through the thin part, so it may be causing a minor vacuum leak. Could that be it? I got so hasty at the last minute you wouldn't believe it.

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Old 07-22-2008   #6 (permalink)
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Re: IAC valve issues.

Yes, that could definitely be causing issues. That o-ring needs to seal perfectly.

Idle re-learn is easy. After you reset the ECU, turn the car back on and don't fuck with it for like 15 minutes. Everything should be off (radio, lights, de-frogger, etc..).
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Old 07-22-2008   #7 (permalink)
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Re: IAC valve issues.

Quote:
Originally Posted by speedfoos View Post
Yes, that could definitely be causing issues. That o-ring needs to seal perfectly.

Idle re-learn is easy. After you reset the ECU, turn the car back on and don't fuck with it for like 15 minutes. Everything should be off (radio, lights, de-frogger, etc..).
Why do you call it an 0-ring? The only o-ring on the intake gasket is a metal ring through which the coolant flows. The rest is some weird cardboard type material.
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Old 07-22-2008   #8 (permalink)
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Re: IAC valve issues.

Reading owns me. I thought you were talking about the TB to IM o-ring. .....Wait a minute. You edited your post. I could have sworn you said you tore the TB gasket. Looks I need to start quoting folks again.
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Old 07-22-2008   #9 (permalink)
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Re: IAC valve issues.

Quote:
Originally Posted by speedfoos View Post
Reading owns me. I thought you were talking about the TB to IM o-ring. .....Wait a minute. You edited your post. I could have sworn you said you tore the TB gasket. Looks I need to start quoting folks again.
I was originally talking about the TB and how I cleaned the IAC, but as for the post you replied to, I never mentioned which gasket so I changed it.

Do you think I could be getting IAC issue from a small intake gasket leak? (air not coolant) Also I've been smelling sulfer as of the past 2 weeks. What the hell? Catalyst converter?
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Old 07-22-2008   #10 (permalink)
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Re: IAC valve issues.

Sulfur? That's a weird one. Burnt coolant smells like pancakes and syrup, not sulfur. Yes a leaky IM gasket on your Civic could cause IACV issues. Any leak in the IM will cause weird problems. I'd fix that first before you try to troubleshoot anything else.
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Old 07-22-2008   #11 (permalink)
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Re: IAC valve issues.

Thanks. Parts arrive thursday, so I should be doing all this stuff on friday after school. I am going to clean the IAC, FITV, and EGR, then do another TB cleaning since I could have gotten more stuff off last time. Then I will check RPM.

One thing is for sure, after the ECU reset and idle learn, my car still doesn't behave right. It works semi-normal now, but the power isn't there. It's like I'm carrying a full load of people. -_-
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Old 07-22-2008   #12 (permalink)
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Re: IAC valve issues.

sounds like a clogged cat
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Old 07-22-2008   #13 (permalink)
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Re: IAC valve issues.

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sounds like a clogged cat
Clogged with what? Maybe I got a cat sucked into the intake? Do cats ever need to be replaced? Can I clean it myself?
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Old 07-22-2008   #14 (permalink)
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Re: IAC valve issues.

Sometimes the catalyst element will break loose in the cat and fall causing a blockage. The element is a very fine honeycomb, ceramic-based material that if it gets cattywhompus (technical term) in there it will block the exhaust. This isn't very common unless you've removed the cat and banged it around a bit or you happen to own one of the rare ones where the cat just goes bad. Fix the intake manifold leak issue first and then we'll see what's what.
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Old 07-22-2008   #15 (permalink)
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Re: IAC valve issues.

if youve ever seen a new cat, it looks clogged already lol. but running rich can ruin it in no time. ive heard alot of case where it hurts performance. heck even importtuner tested an older maita and they gained something like 15 whp just replacing the messed up cat.
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