Inextricabledrvr

have a 97 Prelude with 222,000 miles. I recently started to have some issues with my idle after I cleaned out my EGR ports.

Here is my issue:

When fully warmed up, the RPM will stay between 1000-1100 and then hang there. Sometimes it will drop down to 750-800 and other times it'll just stay up around 1000-1100.

And yes, I have cleaned my EGR valve, ports, IACV, turned FITV, Cleaned TB, checked for vacuum leaks, Bled coolant. I also tried plugging one of the two holes in the TB and the bottom one made the car stall. Also when I unplugged the IACV the idle would drop to 750 and idle fine.

Im stumped. It's irritating when you are driving and you see your RPMs go down and pause at 1000-1100. :/ Any input would be great.

NOTE* When I cleaned/adjusted everything, it idled back to normal operating temp (700-750), but eventually came back to idling between 1000-1100 after a couple hrs of driving.

lazlong

That sounds like the problem. Cleaning it may not be enough.

Wing8806

You say you plugged one of the 2 holes on the tb, there should be no "holes" open on it.


Post a picture of said holes if possible, also do you have an aftermarket intake installed? If so are the lines ran correctly?

Are the 3 nipples on the back side of the intake manifold open(if they are they should be plugged) or do you have the lines still installed? (closest to the throttle body)

Have you adjusted your TB? Are you throwing any CEL's?

You said you unplugged the ICAV and it idled fine... it's possibly bad, Try swapping with a known working one with a local 'luder to see if that's the issue.

Did you by chance use seafoam or pull the ports etc and do it by hand? Is your PCV valve working?

Inextricabledrvr

1) The holes are on the inside part of TB. Their are 2 holes on the inner part.

2) All 3 nipples are closed either with a plug or with a hose.

3) No I haven't adjusted my TB. No CEL's

4) I will try to find someone with a working IACV and hopefully that fixes it.

5) Yes, I did seafoam the car. I pulled the ports on via DIY on one of the prelude forums. PCV valve is new

Inextricabledrvr

I then plugged both holes in the TB and the idle dropped to perfect idle. From what I was reading online, this is a sign of a bad IACV. Someone correct me if im wrong.

holmesnmanny

It is imperative to never spray carbon cleaner into the iacv when it's anything but stone cold as carb cleaner swells seals when hot.

Also, it's really easy to spring a tiny crack in a vacuum hose, especially at the end, but sometimes in the middle, and it not be totally apparent. Given the work you did there are a lot of vacuum hoses you had to move. I would replace them all. You can get bulk hose from the auto parts stores. They come pretty cheap. The very ends of old vacuum hoses also wind up being spread out over time, making it easy for air to escape. Also, make sure to get new gaskets for the iacv fitv and air boost valve whenever u remove them if they're old. It could be leaking there as well.

holmesnmanny

When you unplug the iacv it's supposed to close. This is what you do to set the base idle, assuming no vacuum leaks. If it's still open at the top port after being unplugged do to a defect then when you close it at the top port on the inside of the TB this should bring it down to 500 to 550 rpms simulating base idle.

Inextricabledrvr

I'm going to Autozone to buy some new hoses and just replace all the hoses. Which one is the air boost valve? I really appreciate your input. I am going to tackle this problem right now and hopefully I can get it fixed.

Inextricabledrvr

So, I asked a friend of mine with a good IACV to switch it out and see if that was the problem. And it was! It idled perfectly with his IACV! Problem solved! Thanks everyone!

Wing8806

good to hear man! It's always nice to have someone local that you can swap parts with to make testing easier vs buying something that doesn't fix it

Inextricabledrvr

Thanks for your input btw!

Inextricabledrvr

Idle problem has returned!? The idle will surge from 1K-1500 when I suddenly brake while driving. It'll also do it when I am idling and I pump my brakes. I know it's weird. I've been trying to troubleshoot this for the pats couple days.

I bled the coolant again, replaced hoses around the TB, Cleaned IACV, Screwed in fITV again, cleaned tb.

Im clueless on whatelse it can be. :/

Wing8806

Happens when you idle and pump the brakes? hmm have you checked the condition of the line going from the brake booster to the intake manifold?

Inextricabledrvr

I took a look at that, but didn't see anything out of the ordinary. I'm gonna check tomorrow and spray that tube down with carb cleaner to see if I get any type of surging, bouncing etc.

Idle problems are such a PITA. It only fluctuates from 1k-1500 when I brake hard...or when I pump the brakes at idle. The idle is still a bit high every other time the idle will "hunt' or "hover" around 1k. When I cleaned everything again, it idled perfectly and then I drove it around a little and then it came back. :/

Inextricabledrvr

Here is a video:

Wing8806

I'm pretty much out of ideas as to what it could be, seems the only thing you've not replaced/tested involving vacuum lines is the egr solenoid sitting on the driverside shock tower. But I don't see that causing an idle issue when pumping the brakes....

I'll search around but i'm at a loss otherwise :/ sorry man.

Inextricabledrvr

I am still going to check the that booster line for any leaks. I've been reading online that there is a test I can do from the Honda manual for any leaks.

Possible bad brake booster?

I've never seen a problem like this before. I'm just going to spray all the vacuum lines with brake cleaner and hopefully something shows up.

I really appreciate your input with my problem. I hope I can figure this thing out. :/

lazlong

I had the EXACT same problem with my EM2. After cleaning everything, and I mean everything, and spraying carb cleaner to find a vacuum leak it was still idling weird. I even inspected the booster hose and tested the valve to no avail. I got to thinking maybe I missed something on that booster hose. $30 and about an hour of swearing later she idles fine. Moral: Just because the hose doesn't look bad doesn't mean it isn't bad.

Inextricabledrvr

I appreciate the input man. I've been swearing and cussing believe me. :/ So, you are pretty much saying replace all the hoses. I'm also going to check the brake booster hose and valve as well.

Inextricabledrvr

I was able to look around and I noticed my PS hoses have a leak. My clutch reservoir hose also has a leak. Could these be possible causes? Man, I might as well just buy all the hoses for this car. lol

holmesnmanny

Any car that has a brake booster on it will surge if you rapidly pump the brakes. This is normal. However yours is worse than normal.

You have a vacuum leak somewhere. Did you install a new intake manifold gasket and make sure to remove every single piece of the old one ? To do this the best way, you would need to remove the studs. To do that you need to put two of the nuts together on each stud and tighten the nuts together, then use the inner one to remove the stud by turning it out. Then use a gasket scraper to gently remove all old material.

Did you install all new gaskets/o-rings for the air boost, fitv, and iacv ?

It's also very easy to have a leak near the injector rings where they meet the IM.

Inextricabledrvr

No I haven't replaced the IM gasket yet. No new gaskets/rings for any of the above listed. The only one i've changed recently is the EGR valve gasket.

Although when I replaced my VC gasket I did remove the injectors to see how dirty they were. I'm going to have to doublecheck to make sure they aren't missing any o-rings and are probably seated. I will update when I get the chance to check all these possible problems. :/

holmesnmanny

Did you make sure to remove all the old egr valve gasket material ?

If you did the egr ports is it safe to assume you removed the IM from the car ? If you did, it is possible to reuse the old IM gasket but only if it was completely undisturbed and still in perfect condition. Otherwise it's best to replace it, making sure to remove all the other gasket.

Inextricabledrvr

^^^^ Yes I removed as much I could on the EGR valve gasket. I did not remove the IM when I did EGR ports.

redef90si

iTrader: (3)

If you are wanting to try another Known good H22 IACV I one for sale(link in my Signature)


Best of luck either way,I'd for sure check all the hoses for Vacuum leaks first,Matt.