99 Si idle surge at 1800 when coming down in rpms.

smrtss2

Anyone want my front end?
5+ Year Member
On my way to work after the first really cold night we've had my engine stalled and died with no shudder or warning when turning into a parking lot. It was running fine in my driveway while I was scraping the frost off the windshield with the defroster on high and was running fine until I made the turn then it didn't seem to want to start and I had to crank it and keep my foot on the throttle to keep it alive, came back to life and was idling fine. I drove it back home, parked it and took my other car to work. When I got home I hopped in it and let it idle til the rpms came down (it fired right up) and it revved and idled fine until I noticed it "surged" a bit when the rpms were coming down and at about 1800 is when it surged then it hit normal idle and it was fine. I kept revving and letting off and it consistently does it and you can feel the surge in the motor. Only mods I have that might matter are DC intake, Apexi cat back, and HIDs.

Fuel system seems to be fine
Shouldn't be a vaccum leak as there's no irratic idle thru the range.
Can't be the alternator since it fired back up (thought maybe it was the HIDs drawing too much power with the defroster blasting).

I have a neighbor bringing a code reader home from his store and I haven't cleaned the intake (new filter tho) since I bought it 5 weeks ago and I'm new to Hondas and wondering what would cause it to die out of the blue and make the rpms surge only on the way down when not on the throttle at all?

What intake parts do I need to clean and where are they?
What might it be?

Oh and I did search thru the forums and didn't find anything but some that were semi-related but none seemed to have this problem. I apologize if I missed it, any help would be great as this car is becoming a giant pain in the ass and I'm almost at the end of my rope and wanting to sell it.
 

RonJ

Banned
You have owned the car for 5 weeks. Have you yet done a basic ignition system tune up (plugs, wires, cap, and rotor)? Did the CEL remain on while driving? Does the CEL work?
 


smrtss2

Anyone want my front end?
5+ Year Member
I was hoping you'd chime in. Plugs, wires and distributor are all recent. Plugs were checked the day after I bought it are fine and the Check Engine Light works and didn't come on at all (any tampering with the CEL or other notification lights and NOT telling the buyer is a crime in this stye and the previous owner can be sued or forced to buy the car back and recoupe losses and I told him that).

Any ideas?
 

RonJ

Banned
How many miles on the engine?

Regarding the stall, what kind of plugs, wires, and distributor did you install? Was the entire distributor replaced?

Regarding the idle surge, you may want to start by cleaning the throttle body and IACV and checking the throttle cable adjustment, which should have about 1/2" of free play.
 


smrtss2

Anyone want my front end?
5+ Year Member
178,000 miles, Denzo plugs (not positive? I checked them weeks ago and no notable carbon build up) all look to be firing, the guy said he did a cap, rotor and wires at 150,000 and that looks to be true. Throttle cable has play and the throttle body looks just fine with barely any build up.

Where's the IACV and how do I clean it if needed?

It only did it that one time in the 5 weeks I've owned it. There was one other stall but that was more likely due to the clutch pedal being broken.
 

RonJ

Banned
The IACV is located at the bottom of the throttle body. It is connected to 2 coolant hoses. Clean it with carburetor or brake cleaner.


 

defvayne

Set This World On Blaze!!
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10+ Year Member
Check your battery. Sometimes its not holding charge due to the weather. I've had that happen before. Check the alternator while you are at it. To make sure its not the batter/alternator. Try running the car on with nothing on. Then turn the headlights and radio. If it starts to surge its the battery no holding charge or the alternator not doing its job right.
 

smrtss2

Anyone want my front end?
5+ Year Member
Shot some carb cleaner into the intake and cleaned the throttle body and drove it the 40 miles to work and it seemed fine. Hopefully it stays like that.
 

MyNaSi51

MyNaSi51
5+ Year Member
mine has simillar problems but my iacv is behind the manifold its a b16a2 2000 si
 

RonJ

Banned
mine has simillar problems but my iacv is behind the manifold its a b16a2 2000 si
99-00 Civic Si throttle bodies and IACV should be identical as shown in the diagram. Post a picture of your throttle body and what you think is the IACV.
 

MyNaSi51

MyNaSi51
5+ Year Member
then whats the 2 p connector on the back of my manifold im gonna go get a picture now. but after replacing the fan switch the car seems to be doing better, the fan is coming on, but it was weird i was doing some voltage checking on the coolant temp which is ground on green and between .7 and .94v's on the red and white. let me go check
 

RonJ

Banned
then whats the 2 p connector on the back of my manifold im gonna go get a picture now. but after replacing the fan switch the car seems to be doing better, the fan is coming on, but it was weird i was doing some voltage checking on the coolant temp which is ground on green and between .7 and .94v's on the red and white. let me go check
My mistake. The previous diagram I posted was mislabeled. You are correct. The 99-00 Civic Si has the IACV on the back of the IM.


 

MyNaSi51

MyNaSi51
5+ Year Member
ok cool no need to post my pictures. i was thinking someone before switched manifold and tb. but anyways since i replaced the fan switch the car still idles at 900 but for now the surging only seems to b for a second after reving, keep in mind i havent driven it, this problem has drove me to have a drink so im parked in the garage for tonight but its hot enough for the fan to kick on, but something is still not right. are you suppose to be able to move the injectors like twist them? they seem kinda loose. the raditor and fan are new due to front end damage prior to me owing it so i know thats not clogged. i cannot find a vaccum leak anywhere. im gonna read my codes tomorrow at work and see if its still throwing a p0505 code. should just try to keep cleaning the iacv or do u think thats not it? the hotter it gets the worse it is.
 

MyNaSi51

MyNaSi51
5+ Year Member
could a tb gasket cause this? i was thinking when the hoses get hot the get loose and the vac lines that dont have hose claps on them might expand only when hot and cause vac leak? im over this problem guys please any more thoughts? should i just bite the bullet and buy the iacv ? is it ok to drive car like this intill after christmas?
 

RonJ

Banned
Wait. Can you post pictures of your IACV and its location. My Y8 engine has the IACV attached to the bottom of the TB and the B16A2 should be the same. I think.
 

Szady

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My mistake. The previous diagram I posted was mislabeled. You are correct. The 99-00 Civic Si has the IACV on the back of the IM.]
As are all D and B Series engines, except for the y7 and auto y8's.. The y7/auto y8 has the IACV on the throttle body, and is a 3 wire/pin IACV.

What you originally posted is a FITV (Fast Idle Thermo Valve). ;) (Unless its from an auto y8).
 

Szady

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10+ Year Member
Wait. Can you post pictures of your IACV and its location. My Y8 engine has the IACV attached to the bottom of the TB and the B16A2 should be the same. I think.
Because your y8 is auto. Auto y8's are just like y7's, IACV wise. :thumbs up
 

RonJ

Banned
As are all D and B Series engines, except for the y7. The y7 had the IACV on the throttle body, and is a 3 wire/pin IACV.

What you originally posted is a FITV (Fast Idle Thermo Valve). ;)
Both my Y7 and Y8 have the IACV attached to the TB. Both diagrams I posted came from the 96-00 Civic service manual. 96-00 Civics don't have an FITV.
 


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