Hey guys,
I have searched a lot and cannot find anything to answer my question. I have a very high idle (about 3k rpms) and when I plug the two holes inside the throttle body before the butterfly, it levels out. I tried taking it apart and I think the two holes lead to the little electric connection on the back of the throttle body but I'm not sure. I took apart the entire throttle body except for the plug because I couldn't find a screw or anything to release it. I also cleaned and tightened my FITV so I know it isn't that. I guess what I'm trying to say is, does anyone know how to fix this? Or can you point me in the way of a useful thread please? THanks guys in advance!

 

Okay, so I found the actual IACV and took it apart to clean the little carbon filter. It was very gummed up so I shot it with some carb cleaner and got it clean. I put it back together and it still idled really high! Someone please help me!!

 

Ive got the same problem man, and this seems common because there are a lot of threads about it. I dont know what to tell you because i cant figure it out either. check all the vacuums, and fitv, and iacv. mines idling at 2k, and gas i stoo expensive for that. let me know if you figure out whats causing it, cause id like to know also.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by scrubachu &raquo;</TD></TR><TR><TD CLASS="quote">Ive got the same problem man, and this seems common because there are a lot of threads about it. I dont know what to tell you because i cant figure it out either. check all the vacuums, and fitv, and iacv. mines idling at 2k, and gas i stoo expensive for that. let me know if you figure out whats causing it, cause id like to know also.</TD></TR></TABLE>
Yea, I checked and retightened my fitv, cleaned the filter on my iacv, and checked all my vacuum lines because I can stall the car when I put my hand over the throttle body.

 

im stumped too man.... my next attempt will be installing a new tb gasket. its cheap, and easy to do. other than that, i dont have a clue...

 

Clean the EGR valve...

 

my egr is disconnected. thats why im running a p28

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gerhard &raquo;</TD></TR><TR><TD CLASS="quote">Clean the EGR valve...</TD></TR></TABLE>
I'm running a p28 too but my EGR is still hooked up. Any other ideas? Thanks for the help so far though!

 

Bump for more suggestions.

 

you said you cleaned the iac but do you know if its working?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by brolli &raquo;</TD></TR><TR><TD CLASS="quote">you said you cleaned the iac but do you know if its working?</TD></TR></TABLE>
Yes, I cleaned the screen that was filled with carbon out. HOwever, I cannot tell if its working, but when the intake is off, I can plug the two holes in the throttle body before the butterfly, and it idles much better. I don't know if this means anything though.

 

both of mine work becaue they are both new from honda.

 

Well, its been suggested to me that the idle could be a product of a bad coolant sensor telling the ecu that the motor is really cold causing the idle to rise. I don't know if this makes a difference to anyone, but I am turboed using a p28 with uberdata for tuning. If that helps anyone please throw me any suggestions! Thanks!

 

My prelude had this problem forever! I finally fixed it after taking my car to an electrician and getting some test. For me it ended up being the IACV itself so I just bought a new one from Honda for like $200 something bucks cause I had tried changing that out before but I still had the idle issue. Another thing that can cause a fluctuating idle is a bad MAP sensor. Best thing to do is borrow these parts from a firend's lude who is working properly and swap out parts one by one to see if you can find the part that is causing the bad idle.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by caLiH22A &raquo;</TD></TR><TR><TD CLASS="quote">My prelude had this problem forever! I finally fixed it after taking my car to an electrician and getting some test. For me it ended up being the IACV itself so I just bought a new one from Honda for like $200 something bucks cause I had tried changing that out before but I still had the idle issue. Another thing that can cause a fluctuating idle is a bad MAP sensor. Best thing to do is borrow these parts from a firend's lude who is working properly and swap out parts one by one to see if you can find the part that is causing the bad idle.</TD></TR></TABLE>
I'll try that, I have a part car thats an si and I will rob the IACV from it and also check my map sensor. Thanks man, keep'em comin'!

 

The two ports that you are plugging are for the IACV and the FITV, I would suspect your problem is the fast idle based on your symptom of a high idle. The fast idle thermo valve is designed to raise the idle when cold. The valve is controlled by a thermowax plunger which is contracted when the coolant around it is cool allowing air to bypass the throttle plate. It expands to close when the coolant gets to operating temp. If the thermowax plunger has failed or there is a coolant issue then this could cause the valve to stay open bypassing air. With the engine running at idle and at op temp, place your finger over the lower port in your TB, you should feel no suction. If you feel suction then the FITV is open when it should be closed (op temp). Check the coolant lines running to your TB, check coolant level, and check for air in the coolant system. If the coolant system is fine and you still feel a suction on the lower port at idle then your FITV is junk.

Its definitely not your egr as one stated becasue the egr is only designed to work at cruising conditions. If it gets carboned up and is even partially open at idle then you would have a very poor, low, and even stalling idle, not a high idle

Most IACV problems I have seen would cause an erratic idle not so much a high idle.s If it is clean I wouldn't worry to much unless there is an electrical issue. Get out a dvom and check for battery voltage between the blk/yel wire at the connector and body ground. If you have voltage the only other thing to check is signal by shorting pins A9 and A26 at the ECM harness (not ecm), the IAC valve should click, if it doesn't the IAC is bad.

If your IACV and FITV systems check out ok then check the idle adjusting screw. At op temp, unplug the IACV then restart the engine. With no load (electrical) and once the idle has stabilized, your rpm be at 550 + or - 50 rpm. After adjusting within this range shut the engine off and plug the IACV connector back in. Start the engine and idle should be 700 + or - 50 rpm after 1 minute.

I tend to get long winded when you put me in front of a keyboard so thanks for bearing with me , I hope this helps.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by h22avid &raquo;</TD></TR><TR><TD CLASS="quote">I tend to get long winded when you put me in front of a keyboard so thanks for bearing with me , I hope this helps. </TD></TR></TABLE>
Hey man, don't worry about it! Actually, thats great advice and I will try testing all that today, however now the idle has changed its mind and it surges from 1000rpms to 3000rpms, but I will still do the checks. Thanks!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by maxvtec7500 &raquo;</TD></TR><TR><TD CLASS="quote">
Hey man, don't worry about it! Actually, thats great advice and I will try testing all that today, however now the idle has changed its mind and it surges from 1000rpms to 3000rpms, but I will still do the checks. Thanks!</TD></TR></TABLE>

ahhh, now it seems like your car is playing cat and mouse. trust me, this **** can drive you mad not being able to figure it out. good luck and hope you nail the problem

 

Now that the issue has resolved itself into one which I have experience with, I have to say that you need to change (not just clean) your FITV. Try the one from your parts car.

 

same thing happened to me, i think i saw a thread about this about a month or so ago. I believe its your cold start valve, which is very similar to the IACV. Does it idle like that when your at lights stopped, going back and forth fomr around 5 or 600 to about 1500 or 2000? Thats what mine did, and all you have to do is adjust the CSV.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .H22 POWER. &raquo;</TD></TR><TR><TD CLASS="quote">same thing happened to me, i think i saw a thread about this about a month or so ago. I believe its your cold start valve, which is very similar to the IACV. Does it idle like that when your at lights stopped, going back and forth fomr around 5 or 600 to about 1500 or 2000? Thats what mine did, and all you have to do is adjust the CSV.</TD></TR></TABLE>
Actually, it surges all the time!! At stop lights, even when I'm driving, which is really annoying. I will try replacing the FITV first and see what happens. And you guys are right, my car is playing a game of cat and mouse, and its winning

 

lol that sucks bro, check those out and get that **** fixed!! You gotta have the upper hand over your car!

 

tried to adjust the idel with the IACV unplugged. the lowest i could get it was 1500 rpm's and it idles with it plugged in at 1800. would a rich fuel curve cause the high idle? im getting crappy mileage on the p28. it has the skunk 2 program on it right now. im gonna change that soon i guess. any other ideas?

wheres the CSV?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by scrubachu &raquo;</TD></TR><TR><TD CLASS="quote">tried to adjust the idel with the IACV unplugged. the lowest i could get it was 1500 rpm's and it idles with it plugged in at 1800. would a rich fuel curve cause the high idle? im getting crappy mileage on the p28. it has the skunk 2 program on it right now. im gonna change that soon i guess. any other ideas?

wheres the CSV?</TD></TR></TABLE>
Yea, I have a surging idle now, so I'm gonna try to replace the FITV or whatever the hell its called and see if that works. If not, I will try adjusting the idle, although I don't know why it would change on its own! I dont' get it!!!

 

I don't know that the fast idle throttle valve is the problem if idle is surging. That would mean that the thermowax plunger is going up and down to open and close the bypass port which is pretty much impossible. It's entirely controlled by temp. when cold coolant is surrounding it then its contracted and when the termowax warms up with the coolant it expands to close off the bypass port. Its only use basically is to maintain a higher than normal and steady idle until the engine gets to opereating temp.

I dunno, I'll sleep on it and let you know if anything comes to mind.