Ri5e

My car idles funny, goes 800 then 1800 rpm then back down, etc.... does it when the car is warm or hot! No CHECK engine lights codes! Car is fine in boost....

I reset the ECU and it idles fine...then a few moments later...bam same thing happens...Here's the story:

I got a new STR Manifold. Everything is hooked up correctly...except for the sensor on the BACK. I believe its the IACV. It has two water hoses going into it and it has 2 holes...one that reads manifold pressure, and the other one, i'm not sure what it is?

Anyways, on the STR Manifold where throtte body and manifold mates, there is the 64mm hole and there is SUPPOSE to be another hole for the throttle body hole thingy (Air from before the throttle plate) but on the manifold it does not have that! That hole provides air or something for that Sensor on the back of the maniofld....but now there is non.

However, on the STR manifold, it has this nipple taht sticks out for air to go into that 2nd hole on the sensor. am i suppose to connect that to manifold pressure? This one guy said to leave it open...

Help! Help me idle fine again!!!

Arturbo

Take off the IACV and shake it, if it makes a rattle noise its no good. Replace it and Im sure it'll take care of that.

art

Smashback

Yeah you're screwed Same thing has been going on with my car for over a year now. Started when I switched the DX head/intake out with the EX ones. They have different IACV's, I'm on my second one, bla bla idle sucks and it's embarrassing.

Normally there is a passage thru the TB that routes thru the intake and into the IACV, and then the IACV dumps the air back into the intake with the second hole. The IACV regulates the amount of air that is allowed to enter the engine at idle to compensate for the AC, lights, etc so that the idle does not drop.

Ri5e

Oh yeah when it idles funny it makes a hiss sound ...like this:

"Vroooom!....hissss!.....Vrooooom!.....hissss!.... ..Vroooom!!......hisssssssss!....Vrooom!....hissss sssss!"

Should I drill a hole in my intake pipe (Right before the throttle body) and get a nippple welded on their and connect a hose from that to the IACV?

Ri5e

Is it possible that I might've pluged in the wrong plug?

PrecisionH23a

here is how my friend hooked his up to his gsr...








which hoses are you confused on? it sound like a iac problem as everyone else stated.


[Modified by GudeH23a, 11:36 PM 8/13/2002]

Ri5e

Damn that is exactly how mine is setup. HOWEVER, ask your friend what he did with the port on teh bottom of the manifold. It is like right underneath the IACV. Its about 1/8th inch in diameter and 1 inch long. did he leave it open or did he connect a hose there to something? I left mine open...and i BELIEVE thats whats causing the problem! This guy told me to leave it open so i left it open and I think that could be the problem. I think i'm suppose to connect a hose from that to the intake pipe or something??!

Ri5e

help

dustin

You mean you have a huge vaccum leak? Hehe.

SuPeRITR

either you have a vacum leak or you have air in the thermostat......but i fyou didnt touch the coolant system then vacum leak.

the IAC vavle works like this, it open and closes inside it to let a certain amoun of extra air to pass through so that you idle steady, because when the throttle plate is closed there needs to be some way to bypass some air so that the car gets enough.

usually the set up on thos sensors is on hose piped to the hole before the throttle plate then another piped to after the throttle plate.....usually thats the way it is, but sometimes honda gets real technical about it and changes it up a bit....so it all depends....i have actually run the car with that sensor totally desconected off the car i mean not just unplugged but removed and the holes pluged and i got no check engine light. but it ran like POOP.....

Arturbo

Well it actually runs like this: Since I dont want to type out how it works Im gonna copy and paste it off of Hondata:
"The idle speed is controlled by three methods:

The cold idle value, which is located under the throttle plate. Late model engines may not have the cold idle valve. The valve consists of a air channel bypassing the throttle plate which is blocked once coolant heats up a wax element. When the engine is cold the cold idle valve will allow a lot of air to bypass the throttle plate, and the idle will be around 2000 rpm. As the coolant warms up the cold idle valve will slowly close, bringing the idle speed down.
The idle air control valve (IAC or EACV), which is located on the back of the intake manifold. The IAC valve is a solenoid which is controlled by the ECU using pulse width modulation. Thus the ECU can control how far the solenoid is open and how much air bypasses the throttle plate. There are limits, both upper and lower, to the amount of air which passes through the valve because the solenoid will only work from 20% to 80% duty cycle.
The throttle air bypass screw, which is located in the top of the throttle body. Unscrewing this will allow more air to bypass the throttle plate, and so will increase the idle speed. The purpose of the bypass screw is to adjust the amount of air going pass the throttle plate so that the IAC valve duty cycle is within the limits of what the ECU can control. The manual tells you how to adjust this screw by unplugging the IAC valve. "

art

Ri5e

I hope this clears some things up! THE IACV (The Mesh Part) is getting no air into it. That might be my problem, but i'm not sure

Heres the bottom of the manifold:


As you can see that nipple part I did not connect it to anything! I have no clue what I should connect it to.

Smashback

Yes, if I remember right the mesh side has to be able to take in air freely. So here's what happens as far as I understand it:

1. The IACV opens to keep the idle speed up...
2. Air is taken in thru the mesh side...on a stock manifold it would be drawing that air thru the manifold and thru a port in the TB which is BEFORE the throttle plate
3. The extra air being taking in is passed into the intake manifold thru the other port on the IACV.


So....hopefully that makes sense. In regards to your IM, the EX manifold does have this passage, but the DX has a totally different 3 wire IACV whereas the EX uses a 2 wire. That's the only reason I had to buy the damn EX ECU

However, mine is still fudged and I have replaced the IACV once, although both that I have are used so I suspect that however unlikely I have two bad ones and I've been spending all my money on go fast parts rather than fix-it parts.

Ri5e

So basically waht that thing does is, it reads the water temp...and if its cold then it sends more air into the intake manifold? Do you think thats why my idle is funny because that thing is not getting air from the intake pipe but instead getting ambient air from outisde the engine?

Also does that thing suck in air or does air have to be "forced" into it?

1fstevo

BG, I have done alot of STR manifold a year ago on a turbo B18C. The nipple you are referring to is for sucking fresh air for the mesh part of the IAC. Look at the hole that should go on to the mesh side then blow in the nipple and you will notice air is flowing from nipple through the hole. It does not have anything to do with internal of the manifold.
Also from what I remembered, you have to drill and tap a hole for the IAC mounting point since STR forgot to drill it or is it just on the particular one we received, I forgot. The manifold will work just like stock, no big secret just make sure you look at the tb and the original stock manifold very well and just follow the plumbing on it. The ups and down I would think it's a vaccuam leak hense spray around the manifold, tb anywher with Thottlebody clean to see if the engine hesistate. If you spray to a section that reflex the idle, then there is your leak.

Ri5e

So just leave that port open? I dont htink there is a vacuum leak beause it idles fine when its cold, it idles at 1,500 rpm...then after like 2 mins when its kinda warm then it starts to make the idle go up and down.

DIRep972

iTrader: (1)

my car did the same thing. it wasnt the IACV, it was the throttle coolant valve(at least thats what i call it) it bolts onto the bottem of the throttle body on OBD1 LS's, and coolant runs through it. art mentioned shaking the IAC, but i think he got that confused with the TCV(i think thats the name), because thats what broke on my car when we shook it to see if it was broke, which it was.

93LSivic

So I take it that I will have to do the same exact thing with my Venom sheetmetal intake manifold when I bolt it to my LS.
Is the IAC really needed? I dont really want to bolt it to the manifold.


[Modified by 93LSivic, 4:17 PM 8/14/2002]

Adi Radoncic

Bg Boost I'm sorry I can't help ya with that problem because I have the same thing going on with my car and I'm running a stock intake manifold.....

When I first start the car up and its cold it idels fine at about 1500-2000rpm but than as soon as it warms up a little bit the rpm's start to fluctuate in the same way, the only thing is that on my car the rpms fluctuate from 1000-3000rpm and with the full 3" exhaust its pritty imbarasing when sitting at stop lights....

On my car I personally think that my IACV is bad but than agian it could be something different...

My question is thou is there any posibility of making something or modifying that valve so it doesn't affect the idle... and I personally wouldn't even mind having to hold the throttle at 2000rpm on a cold start up just to get the car warmed up if i got my low idle back in return...

What do you guys think.....

Adi

Ri5e

Ok, I think i might have a bad IACV because when i unplugged the plug the car idles at 1,100 rpm but barely fluctuates. So I think the IACV is bad. Are they THAT sensitive? because I dont remember banging it up against anything.

And the GRAY Plug goes to it right? I hear that some people accidently plug the Evap purge plug to it, which is the blac plug

pornstarSR

thats exactly what i said but ok, maybe not so detailed

1fstevo

vacuaum leak......