this is for a friend. his 93 dx hatch is slightly surging, not only at stopped idle, but at very slow speeds too. checked iacv and for obvious vacuum leaks, none were found. please help. thanks

 

How high is it surging at idle? You say you can also hear a slight hiss? Does this hiss go away if you plug off the IAC or fast idle thermo valve port in the TB?

 

Its actually my car.
Now Before I start I have read through the posts and the articles and have gone over the car time and time again.

The situation:

I have an Erratic idle after the car warms up. When i First start the car it idles at about 2000 rpm when she warms up finally it drops to about 900 where it acts like it is gonna stall and then goes up to 1300 and back. Kind of sounds like she is purring..

The parts:

The engine is a d15b8 pos with 160k For now. But she runs great just no *****.
The intake manifold is of a 95 delsol s non vtec d15 something so as not to need the reducer for my intake pipe The delsol was mine till it was totalled and i salvaged what i could.
The idle was occuring on the delsol and now it is on the civic. It originally started at like 60 - 70k

My attempts:

1 I changed the map sensor back to the original
2 Ripped apart intake manifold and throttle body and cleaned it changed gaskets
3 checked for vac leak with starter fluid
4 cleaned the crap out of the iac valve
5 no pcv valve or egr valve
6 adjusted idle
7 no cel codes
8 checked tps
9 checked for voltage in wires

Now I am sure i did more stuff but thats all i can think of The main thing though is that it is isolated to the intake manifold for as the other one that was on the car did not do this. It doesnt affect my daily driving but it bothers me and i am sure is hurting it while i warm it up the the cold months.

The hissing sound is just the engine sound coming through the now like 3x's bigger intake manifold ....... i think.. kinda sounds like a blow off valve

Acidrippedhippy

 

If you've gone through all of that and the problem is still there I would first do this. Remove your intake pipe from the TB look inside of the lower left hand portion directly in front of the throttle blade (the one in about the 7-8 o-clock postion). You should also see a port on the top left hand side, this is for the IAC. If you do have this lower port (which I think you should, even tho I don't know exactly what IM/TB you have) plug it with your finger. Does the car still idle the same way? If it does get better then it's your FITV, it works mechanically off of the coolant temperature (bypassing air past the throttle blade to make the car cold idle, once the coolant temp is up it should shut bringing your idle back down). A lot of time these go bad and the FITV spring won't keep the valve shut creating a surge. What I normally do in this case is pop off the TB and remove the FITV off the bottom of it. Pop the end off the FITV opposite of the coolant hose, inside you'll find a slot which looks like a slot head screwdriver could fit into. Simply tighten it up till it bottoms out, this will keep the valve shut and your motor should no longer surge if this is truely the problem. Good Luck

 

ok so i did what you asked and a couple of other things and here is what happened

1. i plugged the hole at 7 oclock and the idle was constant there was almost no vacuum if any

2. i disconnected the sensor next to the hole not the map or iac the black cylinderand the idle jumps high and constant with a cel

3. Plugged iac hole at top and it stalled lot of suction on that one

4. disconnected iac valve wire and idle stabilized at 1000 rpms

any help for me

 

But when you plugged the lower FITV port (7 o-clock) the idle was good, right? If so then it's your fast idle thermo valve, all you have to do is what I described in my previous post and you should be set. Also if that is the case the reason why your idle stablizes when you pull off the IAC connector is because your IAC closes and you no longer have the "extra" air making it's way past the TB (it should normally be going through the IAC but when you have extra bypassing the blade through the FITV then you get what is basically a vacuum leak). If you didn't unplug the IAC or MAP then I assume it was the TPS, it too can cause you problems sometimes if it's above 0.5V+ at idle but I doubt that is the case here. Let me know if I interpreted your findings incorrectly.

 

I'm sorry i meant the idle continued to surge when i plugged the hole at 7

 

Oh okay, the just disregard everything I just said, lol. What does your car idle at with the IAC unplugged? It really seems like a vacuum leak or IAC problem to me now.

 

it idles at 1000 with the iac unplugged and i thought that was the tps but i dont have my book in front of me and wasn't 100% sure.
Man I can't wait till my restrictions up

 

i almost wonder if you idle screw is too far open. i opened mine up a little too much, and now my car idles like 1200 and surges a little bit every now and again. its just a possibility for a small vacuum leak.

 

which way is open matt up or down and i will give it a shot

 

im pretty sure that counterclockwise open the idle screw more, so if you want to try to tighten it a little, take your flathead screwdriver and turn the screw to the right

 

ok so i tightened it all the way in and it is idling at 800rpms let see what happens


Modified by acidrippedhippy at 10:39 AM 11/19/2004

 

thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you thank you

Who would have thought it was the idle screw ...... I bow to those who had the knowledge to help..

Blackeg if you ever need any help just ask

Check this story out..

I did a bushing job on my car and as we all know you need an alignment afterwards. I took it to STS for the alignment and was told the rear bolt were rounded and couldn't be done.. I proceeded to tell them i was just down there and ripped everything apart it cant be... was told well they are.. i told them that if they were i was getting the bolts and they were aligning the rear for free b\c it was them who stripped them... so agreed.. I check it out on my own and they weren't stripped the neverseize was still oozing out of them bolts in fact... so i went back and guess what.... The guy was trying to align the car from the back side of the compensator arm to trailing arm you know the welded nut what a jackass...

Moral of this story..... want experience on cars that aren't yours apply at STS.

 

Glad to hear you got you're problem fixed. I've never seen or heard of the idle screw doing that but so long as the surge is gone that's all that matters.

 

believe me i never heard of such a thing either and it wasnt acting like the idle needed to be adjusted and man what a waste of time cleaning and replacing everything i did no one ever mentioned that once. lol

 

glad i could help