I am under the impression that... When you pump the brakes rapidly your RPM's should gradually go up 300 to 700 RPM's and slowly drop back down to normal. Well this is the impression I got from searching and from my mechanic. Also, in my girlfriends GS-R, when you pump the brakes the RPM's will go up a little and then come back to normal, nice and smooth. So here is my problem...

When I pump the brakes rapidly the RPM's climb to about 1500 then drop very rapidly all the way to basically zero, however the car doesn't die. If you continue pumping the breaks the idle will climb to 1500 RPM's and drop to zero over and over, until you stop pumping the breaks. I thought that this was a brake boster related vacuum leak, however I changed my brake booster and brake master and it didn't this problem. Now I think it's just a general vacuum leak, am I correct? And why wouldn't replacing the booster and master fix this problem?

Another reason I believe it's a vacuum leak is because sometimes my idle will surge. Most of the time it will sit at a constant 700 RPM's but when it surges (mostly when really hot or cold) it will basically drop to zero then come back up to 700 then back to zero and so on. I have read through everything trying to figure this out with no avail.

Help would be greatly appreciated!

 

what year is your car? It could possibly a idle control sensor or something like that. For instance, AICV of something.

Do you have any other idle issues other than the two you mentioned? How does it idle with the air on? On a cold start, does is have a good fast idle and come down normaly? Have you ever messed with your by-pass screw? Did you check to see if your throttle was sticking? DId you ever touch the throttle stop screw?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">what year is your car? It could possibly a idle control sensor or something like that. For instance, AICV of something.
Do you have any other idle issues other than the two you mentioned? How does it idle with the air on? On a cold start, does is have a good fast idle and come down normaly? Have you ever messed with your by-pass screw? Did you check to see if your throttle was sticking? DId you ever touch the throttle stop screw?</TD></TR></TABLE>

Check out my sig. for the car and motor.

One cold start my idle will start out fast and come down pretty smooth. I replaced the mechanical fast idle valve which solved the cold start problem, that's not what is happening now. After a cold start, when it finally levels out at 700 RPM's, that's when it will begin dropping to zero then back up to 700, and continue doing this until warm. Then when the car is really warm, like I beat it hard or it's just like 80* outside, then that's when the idle begins to drop again. It's really confusing, when my car is at medium temperature the idle for the most part remains constant at 700 RPM's.

I must have a vacuum leak, but where? What do these symptoms suggest? I know H22 always have fucked up vacuume problems, but there has to be a reason.

Where is the IACV on a H22? I can't find a visual referenece that will suggest it's location.

There are no other idle issues.

Idles no differently with the air on.

What is a by-pass screw? Do you mean the idle adjustment screw? I am almost positive that it's completely tightened. Would this be bad?

No, the throttle isn't sticking.

What is the throttle stop screw? Is that what I described above?

BTW, thanks alot for your help. This is probably the most frustrating problem I have ever had.

 

doesn't sound like a vacuum leak to me, but what do I know? Typically, vacuum leaks tend to be a constant thing not one that's only intermittent. The throttle stop screw should be some where nere the TB. It's what stops the trottle from fully seating in the bore because if it does, the throttle plate will get jammed.

I seen some people try to adj. there idle with the throttle stop and it makes for some really bad problems. The idle should always be adj. by the by-pass srew, which i think is on the tb also, you'll know it's the by-pass screw because it's pretty big and it's a phillips head I think. But that doesn't sound like thats your problem either unless you know otherwise.

I suggest you but a good manual like helms (always come in hand) or even a haynes manual for your auto store (you can also borrow them for free at your library) and find out how to diagnose you idle air control valve because it sounds like that could be your problem. Although, that's just a guess.

I think on OBD I tegs the only idle sensors are the fast idle thermal valve and the idle air control valve, but I not sure. You'll be able to find that out by searching.

good luck

 

Thanks alot for your help. I will probably just look through my mechanics Honda manual. It is the most detailed guide I have ever seen. It has 500+ pages for just one specific vehicle, for example 1996 Prelude. I am not sure if this is the same as a Helms, but I do know that the Honda manual is around $100. Hopefully I can figure it out.

What does it mean that my idle climbs then rapidly dies when I pump the breaks? That isn't natural, what does this suggest? Vacuum leaking right? I believe that this is the root of my problem. I could care less about the runability right now.

 

BUMP for Answers

 

BUMP

 

It almost sounds like 2 different things. Brakes/booster problem along with IAC valve.

If your brakes are soft (air in the lines) then the booster has to stroke farther when you press the brake pedal. This uses more air, so it disturbs your idle more than it should. Try bleeding the brakes to make sure they're not soft. Then check out the pushrod adjustment. It should be in your manual; look for either replacing the master cylinder or adjusting the pedal height.

Then the IAC valve might be sticky or something. That's the overshoot & undershoot when it's trying to hold your idle steady. When the brake booster gives too big a shot to the idle that makes it even harder for a shady IAC valve to hold a good idle.

Then there's the whole engine-swap business. Troubleshooting the IAC valve might be a little different if you look it up in a shop book for the donor car. Your book would only cover B18 engines.


ps, yeah, I meant the IAC valve... Saab calls it an AIC valve. Kinda like ECU vs. ECM.


Modified by JimBlake at 5:03 PM 5/3/2004

 

just to clarify the aic valve? - the iac valve, right?

 

sorry if i missed sumthing...but i haven't noticed anywhere how this affects your driveability/performance...what's the symptoms in everyday driving?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">sorry if i missed sumthing...but i haven't noticed anywhere how this affects your driveability/performance...what's the symptoms in everyday driving?</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">cold start my idle will start out fast and come down pretty smooth. After a cold start, when it finally levels out at 700 RPM's, that's when it will begin dropping to zero then back up to 700, and continue doing this until warm. Then when the car is really warm, like I beat it hard or it's just like 80* outside, then that's when the idle begins to drop down and up again. The after a little while it ends up going away. It's really confusing, when my car is at medium temperature the idle for the most part remains constant at 700 RPM's.</TD></TR></TABLE>

Performance really affected, just runability. But something that also kinda sucks is, when the idle is surging (actually trying to drop, not raise) and I drive in a higher gear like 4th say going 35 MPH, the car will surge. This implies a vacuum leak to me, right? And it's not my o2, I check it out and tried a good one, it made no difference.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">It almost sounds like 2 different things. Brakes/booster problem along with IAC valve.
If your brakes are soft (air in the lines) then the booster has to stroke farther when you press the brake pedal. This uses more air, so it disturbs your idle more than it should. Try bleeding the brakes to make sure they're not soft. Then check out the pushrod adjustment. It should be in your manual; look for either replacing the master cylinder or adjusting the pedal height.

Then the IAC valve might be sticky or something. That's the overshoot & undershoot when it's trying to hold your idle steady. When the brake booster gives too big a shot to the idle that makes it even harder for a shady IAC valve to hold a good idle.

Then there's the whole engine-swap business. Troubleshooting the IAC valve might be a little different if you look it up in a shop book for the donor car. Your book would only cover B18 engines.


ps, yeah, I meant the IAC valve... Saab calls it an AIC valve. Kinda like ECU vs. ECM.</TD></TR></TABLE>

Brake feel is nice and hard. And my entire brake system was bled correctly when the new booster and master was installed. Pushrod is adjusted correctly also.

I really don't think I have a IAC. This is also know as a starter valve right? Maybe someone can tell me where it's located on the H22. I have the Helms printout of the vacuum diagram page, and it's no where to be found, other then the starter valve located on the front right side of the manifold. Take a look and tell me if it's there. BTW, the starter valve didn't come with the swap and my mechanic said it's not nessicary and most people take it off anyways. This is because when it goes bad it will create a constant vacuum leak.

And I know it's a H23 Helms diagram, but their vacuum lines are susposed to be identical.



Thanks alot guys, keep the hypothesies coming.

 

BUMP for some much needed answers.

 

BUMP for some much needed answers, come on guys

 

it should be on that diagram if you have one and i dont see it - it could be like the starter valve, but that sound more along the lines of a fast idle thermo valve - does the idle go up on its own when you start it cold? - you might try a forum more well versed on h22s - just a thought

 

Changed the fast idle awhile ago, it solved the cold idle fluctuation problem.

I just want to know why my car's idle drops when I pump the brakes?

 

BUMP cause I still need some help.

 

i strongly doubt it has anything to do with the brakes, the booster, or the mc...i think it's more along the lines of the Idle Air Control...lo0k into that.

 

I guess I don't really know the H engines, but that picture looks like you don't have an IAC valve. Judging by the hose connections the 'starting air valve' is close, but that name implies that it doesn't really regulate the idle once the engine's warm.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">I guess I don't really know the H engines, but that picture looks like you don't have an IAC valve. Judging by the hose connections the 'starting air valve' is close, but that name implies that it doesn't really regulate the idle once the engine's warm.</TD></TR></TABLE>

And that's why it's probably been taken off my motor, it's unnessicary. But what controls the idle on the H22, I can't find anything?

 

BUMPage

 

just a thought but it seems like you might have better luck in the prelude forum considering most of us dont have h motors therefore probably cant help

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">just a thought but it seems like you might have better luck in the prelude forum considering most of us dont have h motors therefore probably cant help</TD></TR></TABLE>

I did. But it's mainly the question of why the idle acts the way it does when I pump the brakes. That's by no means an H22 or Prelude related question.

 

Pumping breaks... idle drop???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">if you pump your brakes, and your idle goes up and drop and so on, it is working properly.</TD></TR></TABLE>

How do you figure? I have pumped the breaks on a few Civics and Integra recently, just to see how they react as compared to my car. NONE of them act the same as my car, basically when you pump the breaks on every Honda but mine, the idle will slowly rise to about 1500 RPMs and HOLD THERE until you stop pumping. Then when you stop pumping, it will SLOWLY fall back down to 700-800. When I pump the breaks my idle will rise to about 1500 RPMs and then immediately DROP like a rock to 0, then back up to 1500 RPMs then DROP like a rock back to zero, OVER AND OVER. This process will continue until I stop pumping the breaks. This cannot be right, what could be happening???

Where is the Idle Air Control Valve (IACV) on the H22? If you could, I would really appreciate it if you scanned the Helms page for me. PLEASE