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Revving dropping idle need help

Old Oct 3, 2008
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Revving dropping idle need help

We have a 97 Civic dx 4 cylinder 5 speed car...

Admitted the car has sat undriven a couple months,
Now it has a weird intermitted problem it didn't have when parked.

The idle will be fine and then will start to hunt or fluctuate between 1000 and 2000 RPM ,
Then it will stop doing it for a spell then starts again,
It doesn't stall and the AC being on or off doesn't effect the problem,

Otherwise the car runs super fine,

Anyone have some ideas where to start looking to resolve this annoying problem,

Many thanks
Cheers,
P.
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Old Oct 4, 2008
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Re: Revving dropping idle need help

try to clean out the intake system, IAC valve, throttle body, etc. prolly just clogged up with carbon.
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Old Oct 6, 2008
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Re: Revving dropping idle need help

ya, im thinking ur IACV, throttle body, or ur injectors are clogged a little?

id get deep creap or some carb cleaner and spray the IACV out, as well as the TB and then run some seafoam or something through the gas tank and engine.

my GF's car was the same way after we went on vacation for 4 months to Europe and that's how i fixed it.
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Old Oct 6, 2008
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Re: Revving dropping idle need help

I am dumb to most import stuff computer controlled stuff I work on old junk what is the IACV ?
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Old Oct 6, 2008
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Re: Revving dropping idle need help

its on your throttle body, on the back of your engine.

it has 3 screws holding it in, and has 2 or 3 coolant lines coming out of it.

i cant find any pics on it, but if u take ur intake off and look into the tube, u will see a small hole near the throttle plate. that hole is where ur IACV lets air in, so that it gets past ur closed throttle plate.

btw, IACV: Idle air control valve.

ill see if i can find some DIYs or pics of it. give me time.
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Old Oct 6, 2008
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Re: Revving dropping idle need help

http://www.honda-tech.com/zerothread?id=1575913&page=1

ta-da!
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Old Oct 8, 2008
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Re: Revving dropping idle need help

Many thanks for all the help,
I believe I found the IACV but I was without my metric 1/4 socket set and didn't get in there and clean that yet,
In the meantime I stopped a small new repair shop at the end of my street,
They got in there and said at first it was one then two idle sensors on the throttle body and that you cant replace just the sensors they are built into the throttle body you have to change the entire throttle body, a 500.00 plus part,
He also said that me spraying carb cleaner down the intake is what ruined the sensors, but I had the problem before I sprayed the carb cleaner in there
Does any of that sound right to you guys seems stupid to make sensors your cant change out,
I will still clean the IACV and see what that does

Last edited by The13bats; Oct 8, 2008 at 02:53 PM.
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Old Oct 8, 2008
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Re: Revving dropping idle need help

ur mec is dumb as hell. clean out the throttle body and run 2 bottles of c foam in ur tank ull be fine after that
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Old Oct 8, 2008
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Re: Revving dropping idle need help

technically the sensors are not sold separately, but a used TB off ebay is only $50. i sprayed carb cleaner all over the place and never had a problem. i soaked the iacv in carb cleaner the first time and its still fine years later. its better to clean the tb off the car tho so you can really scrub it. just spraying cleaner wont get all the dirt off.
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Old Oct 8, 2008
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Re: Revving dropping idle need help

Ok,
So I pulled the throttle body and removed the IACV
It had some carbon on/in it and I cleaned it well and the valve in it moves freely,
I reinstalled everything and the idea still fluctuates, just differently now
Also when you first start it now an SRS lamp lights up on the Tach for a few moments and then goes off,
So I still have a fluctuating idle and really need to fix it what should I try next???
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Old Oct 10, 2008
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Re: Revving dropping idle need help

hmm.... thats odd...

take it to a few more shops. dont even tell em what the other place said.

btw, could be sensors (but im not too sure), but could also be like a vacuum leak or something...

sea foam it, and then take it in to get looked at by another 3 or 4 shops.
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