Hey need some advice... ive got a b17 in my 97 hatch. WIth the fuel pressure set to 37psi.. the idle adjustment screw all the way CLOSED, my car is idling at around 600 rpms which is a little low. Also when driving and coming to a complete stop, the idle goes WAY down momentarily to about 2-300. What could be causing this condition? Its obviously not a vacuum leak since it is too low. my only guesses are either injectors or ECu... help please.. Also, the car is throwing a code 36 (unknown) ... Thank you

 

What ECU are you running? Code 36 just doesn't exist in my '92 Helms.

 

If the screw is all the way in(or closed), then that'll make it idle low. If you turn it outward, it'll raise the idle.

 

Thanx but that is no help... im running an obd1 p30 and i know there is no known code 36 but it is still throwing it. Secondly i know about the idle adjustment screw.. The car should still idle perfectly smooth at 800rmp with it all the closed which it is not. Opening the screw basically creates a small vacuum leak which will compensate for the low idle but it is a ghetto fix. What other items to i need to check? Ignition timing possibly? Thank you

 

I think your ECU is shot. To quote the Helms:

"If codes other than those listed above are indicated, count the number of blinks again. If the MIL is in fact blinking these codes, replace the ECM."

 

Heh, atleast yours don't do like my friends, his just cuts off when he stops (stupid Carb). If you have the $$ just go out and replace the ECU, if not then undo the screw a little until you get some $$.

 

The idle adjusting screw is there specifically to adjust the idle. I wouldn't consider a factory adjustment to be ghetto. Here's how you adjust the idle speed from the Helms:

http://webpages.charter.net/mrfatbooty/pics/idle_1.jpg
http://webpages.charter.net/mrfatbooty/pics/idle_2.jpg

I honestly think the ECU and the idle are separate issues. You should be able to fix the idle even if the ECU is messed up like that. Idle is essentially controlled by a number of mechanical means.

All of this aside, you could have a bad IACV which would explain the almost dying when you come to a stop. When exactly does each weird thing with the idle happen? Is the motor hot, is it cold, does it do it all the time? We're going to need the whole story before a proper diagnosis can be made.

 

Do you honestly think the idle adjustment screw is supposed to be all the way in? That's what it's there for, to adjust the base idle speed. Even if it's all the way in, it still lets a small amount of air past the throttle plate, creating a "small vacuum leak" in your words. If anything, if you have the screw turned all the way in, and it's still idling at around 600, it's actcually idling a bit high, since most cars will stall out with the screw all the way in. Mike brings up a good point about the IACV. If you're trying to set the idle speed with the IACV connected, you are not going to get a consistent idle. The IACV raises idle above the base idle set by the screw. The IACV controls how much additional air is let past the throttle plate in order to raise idle speed to warm up the engine faster. If your car is dying when you come to a stop, it's probably because you set your base idle with the IACV connected, and then when you start driving, the engine warms up. When you stop, with the engine warm, the IACV shuts off, and your idle speed drops to the screw setting, which is obviously low, since you have it turned all the way in. If you want a consistent base idle, you have to set it with the IACV disconnected. It wouldn't hurt to jump the service connector as well. If you throw an IACV code while setting the idle, just reset the ECM afterwards. If you feel setting base idle speed via the factory adjustment screw is a "ghetto fix", then I guess I can't help you.

 

I understand what you guys are saying... my point is that i myself have NEVER heard a stock civic si w/b16 hisss like my car does with the idle screw somewhat open. ALso, with the idle bleed screw open, ive noticed that when cruising and letting off the gas to come to a stop, the rpms wanna hang much higher due to the additional amount of air being let in past the throttle plate. This doesnt seem right to me. Heres a few of things that I think could be causing it..

-faulty throttlebody gasket (internally)
-faulty Fast idle thermo valve
-faulty ECU
-faulty or dirty injectors
-incorrect ignition timing

Could any of these be causing this condition? I fail to see the point of disconnecting the iacv when setting the idle.. how would that change anything? the thing is computer controlled...? Thanx for the help!

 

It's really quite simple. The IACV regulates idle speed above the base idle set by the screw. When the coolant running thru it is cold, it idles faster, when the coolant is up to temp, it shuts off, and lets the screw determine the idle speed. Chances are, when you're setting your idle speed, your engine/coolant are not completely up to operating temperature. If you don't disconnect the IACV, it will throw off the base idle setting that you're trying to dial in. If you set the idle with the IACV disconnected, and then reconnect it, the idle speed will probably jump up a couple hundred RPM. Set the idle speed with the IACV disconnected, reconnect it and jump the ECM if necessary. When you start the car again, it'll seem to idle high because the engine is cold and the IACV is idling the engine faster to warm it up. Once it's warmed up, it'll shut off, and idle will drop to the speed set by the screw. A properly functioning tb and idle adjusting screw will not cause an external vacuum leak. I suggest you find the source of the leak before you try setting a consistent idle speed.