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97 civic DX
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51 Posts
Discussion Starter #1
Hey guys, in the morning when the car is cold the rpms shoot up about 2500 rpm which is ok but after the car warms up and even if I take the car out for a while the rpms only drop to about 1900-2000 rpms. When the car is in motion and I take out the clutch the rpms stay at 2500 and when the car comes to a stop they drop to 1900-2000 rpms. The funny thing is that when I turn off the car and then turn it on again the rpms drop to around 900-1000?? The car doesn´t throw cel codes or nothing. Why can´t the rpms drop until I turn off the car? Also, when the rpms are at 2000 and I unplugg the IACV the car throws a cel code and the rpms are unstable and go up and down around 1400-1500 rpms. Help? :-|
 

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97 civic DX
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51 Posts
Discussion Starter #4
Idle adjust screw ?

Clean IACV ?

What voltage is map sensor at ? CT and WOT. (when car is off ofcourse).
I actually never thought about the map sensor but I got a missing link installed because I got the stock map. Also, It´s been about two times that I´ve had to adjust the idle screw so I can raise up the rpms because the first time the idle dropped to about 400 rpms at idle. Another thing I noticed was that the AFR also dropped from being at 14.7-15-6 to 17.2-20.0 when on idle.
 

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5,878 Posts
EXTREMELY COMMON

IACV goes out. it mounts on front of throttlebody, facing motor



me and a buddy went through like 7 junkyard throttlebodies "guarenteed 100% working" before finding one with a proper idler.


quick test, plug the hole in the front of the throttlebody (remove airbox)

if it idles low but even, back out the idler adjustment screw, block off the =IACV with a piece of cardboard as the gasket, and drive until you can aqfford a NEW IACV
 

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97 civic DX
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51 Posts
Discussion Starter #7
Ok just got done cleaning the IACV and the throttle body and fired it up but still the same thing. Well, maybe a little better but I still have the same issue. Also, mattliston I tried your quick test and it idles low but even as you said so I guess the problem is the IACV! Thanks for ur help and now off to buy a new one....

One more thing, with the current problem I have right now does it affect the AFR and performance?
 

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1,885 Posts
is the throttle cable adjuster too tight? is it holding the throttle open? loosen the adjusting nut and pull it out of the bracket as a quick 2 minute test.

-Luke
EDIT: nevermind re read the whole post, doesn't line up with what you posted
 

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\/ apply baby lotion here \/
'98 Civic 4 Door
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11,260 Posts
Y7's tend to do that when you put a y8 IM and reuse your y7 TB. I had that problem for a long time.

Do you still have the y7 rotor cable or you have a y8 rotor cable? That could be one.

or maybe it's too tight and it could be also that the TB is kinda dirty along with the rotor inside and they get stuck so when you let go of your gas pedal, it don't shut right.


just remember, nice n shut TB = smooth normal idle
 

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97 civic DX
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51 Posts
Discussion Starter #12
OK, I readjusted the nut, cleaned the TB, and finally got the rpms to stabilize to normal. The idle seems fine but now when im on the road as soon as I let go of the gas the AFR goes to 20.0 stays there until I push the gas again and feels like the car is about to turn off. Exactly like when you turn off the car with the gears in and clutch out, it starts to slow down fast. Could it be that the TB is maybe too shut?
 

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97 civic DX
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51 Posts
Discussion Starter #14
I got a Wideband Prosport AFR gauge along with Boost and Oil Temp. Before the AFR on idle would be around 14.8-15.6 but now its 17.2-20.0. Any ideas on why? Also got a FPR with 45-55 psi.
 

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97 civic DX
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51 Posts
Discussion Starter #15
Just now I got done cheking out the spark plugs and what do you guys think about them? They are ZFR5FGP. Could be the cause for low AFR....







I am planning on changing them for some NGK bkr7e (4644) which are 1 step colder right? or is it two?.....
 

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1997 Honda CRV
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417 Posts
Take radiator cap off and check coolant level. Also check for a bubble in the system. Adjust idle screw accordingly. Take off TB and IACV and fast idle valve assembly clean them all. Clean map sensor hole with tooth pick. Standard tune-up plugs, wires, cap, rotor. Check all grounds. That should solve the problem. Report back if problem continues.
 
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