Idle bounce's up and down
Moderators: RedRacer, spiffyguido
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redlude
- Prelude Enthusiast
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Idle bounce's up and down
I have a 1990 prelude si with 2.0 motor with pgm fuel control.When I start it in the morning it idles high right away, after it warms up, the motor idles up and down ( from 1200 to 2400 rpm's).If I put it in gear ( Reverse or Drive) it doesn't bounch up and down but the idle is still high.If you let`off the brake the car will go 35 to 43 MPH on its own.Can any one help.I have had it to a few garages and a couple back yard machanics, and the are still scratching there heads.I dont have the finances to take it to a dealer.Please help.........
Last edited by redlude on Thu Feb 21, 2008 7:28 pm, edited 2 times in total.
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spiffyguido
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It's your Fast Idle control valve. This is a common problem.
Your fast idle valve is positioned verticalled on the fire-wall side of your intake plenum, adjacent to your throttle body. It will have coolant lines running to it.
How to fix:
In some cases, all you need to do is take the cover off the top of the valve (two screws) and re-thread the plunger. Once you've taken the cover off the valve, you'll see a (usually white) knob inside the valve with a slot. This is the head of the plunger. You can thread it down with a flat head screwdriver.
If that doesn't work, you may opt to take the fast idle valve assembly off the engine and replace it with a different one. These are easy to find at an auto wrecker, and in my experience, replacement has fixed the problem every time. You can even try to clean and refurbish the one you have. Be sure to be careful with the coolant lines during disassembly and reassembly. Never work with coolant lines when the engine is hot, and make sure you bleed the cooling system once you've put everything back together.
http://www.harleyc.com/prelude/faq/imgs ... ations.gif
Your fast idle valve is positioned verticalled on the fire-wall side of your intake plenum, adjacent to your throttle body. It will have coolant lines running to it.
How to fix:
In some cases, all you need to do is take the cover off the top of the valve (two screws) and re-thread the plunger. Once you've taken the cover off the valve, you'll see a (usually white) knob inside the valve with a slot. This is the head of the plunger. You can thread it down with a flat head screwdriver.
If that doesn't work, you may opt to take the fast idle valve assembly off the engine and replace it with a different one. These are easy to find at an auto wrecker, and in my experience, replacement has fixed the problem every time. You can even try to clean and refurbish the one you have. Be sure to be careful with the coolant lines during disassembly and reassembly. Never work with coolant lines when the engine is hot, and make sure you bleed the cooling system once you've put everything back together.
http://www.harleyc.com/prelude/faq/imgs ... ations.gif
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redlude
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spiffyguido
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Golly. Who gave you that advice?redlude wrote:Also , I read that you said to make sure that I bleed the coolant system after reinstalling it, is there a right way and or a wrong way.I was told to just leave the cap off the radiator and let the car run for 25 to 30 minutes.
No. Seal everything up (rad cap on) and start the engine. There is a bleed bolt on the thermostat housing that you open up slowly when the engine is hot. Let fluid flow out of the check bolt until there are no more bits of air coming out. Top up your reservoir and be on your way. Best to do this one level ground.
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redlude
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spiffyguido
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redlude
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Today I installed a brand new "Fast Idle Valve" that I got from a dealership. It still does the idle hopping.Here is exactly how I done it, {maybe I did some thing wrong}.I disconnected both battery cables from the battery(this supposely erases the computer), then replaced the fast idle valve, I reconnected the battery terminals, and started the car ( which was about 20 minutes later).right away the car idled high (which I antisipate should due to the cold weather),then after warming up it started to idle hop again.I cracked the air port on the thermostat housing to release air from the cooliant system, and let the car run for about 15 minutes. I drove it around for about 20 minutes,then shut it off.About two hour later I went to start the car and it was idle hopping even at high idle,after warming up the hopping still continued.I dont know what or were to go from here, so if any one could help I am all ears.
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spiffyguido
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Redlude,
That's really strange. That fix has always worked for me and lots of other people. Before you rule the fast idle valve out, check again to make sure that your coolant system is bled correctly. If there is no hot water getting to the fast idle valve, it won't work. Double check the plunger in the top of the new valve as well (should be fine). Make sure the Fast Idle valve is well sealed against the plenum.
If it's still a problem, start checking your vacuum lines. This is time consuming, as cracks can be hard to see. If you put some soapy water in a spray bottle and spray the hoses it will help you find leaks as you'll likely get some bubbles forming over a crack.
Keep hitting us back. We'll keep helping.
That's really strange. That fix has always worked for me and lots of other people. Before you rule the fast idle valve out, check again to make sure that your coolant system is bled correctly. If there is no hot water getting to the fast idle valve, it won't work. Double check the plunger in the top of the new valve as well (should be fine). Make sure the Fast Idle valve is well sealed against the plenum.
If it's still a problem, start checking your vacuum lines. This is time consuming, as cracks can be hard to see. If you put some soapy water in a spray bottle and spray the hoses it will help you find leaks as you'll likely get some bubbles forming over a crack.
Keep hitting us back. We'll keep helping.
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RedRacer
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- Prelude Model: 1995 Si w/mods
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Redlude,
You didn't let too much coolant out when you tried to bleed it, did you? Low coolant level will cause idle bounce as well.
Like Spiffy said, it's almost always the IACV that causes this problem and since you replaced it, I really think it's working but that you still have an issue with the coolant levels / air in the coolant.
Top off your coolant, at the radiator, not the overflow bottle, and then bleed it again. There may still be air in the coolant. Bleed it out a couple of two or even three times.
Leaving the radiator cap off, turn on your engine, and loosen the bleeder valve screw. You already know where it is, but to find it, just follow the upper radiator hose to the water neck, there will be a mess of sensors hooked up right after this, the bleeder valve is the 12mm (I think) bolt with a hole in the middle of it. Keep this valve open until pure coolant is spilling out, no air at all, then tighten it down. Top off your coolant again, and run your car for a bit more w/ the valve tightened and the cap down. Repeat a few times until all of the air is out. *don't rev the engine or anything, just let it run.
You can also try screwing in the screw on the fast idle valve... Flat Head, located on top of the Throttle Body.
If the surging stopped once the engine was warm, I'd rule out vacuum leaks. BUT, since it keeps on even after the engine is warm, try the bleeding a couple more times and really let it run clean.
And if that doesn't solve it, then start looking for vacuum leaks like Spiffy said. Spray bottle with water and dish soap works great.
Keep us up to date....
~ josh
You didn't let too much coolant out when you tried to bleed it, did you? Low coolant level will cause idle bounce as well.
Like Spiffy said, it's almost always the IACV that causes this problem and since you replaced it, I really think it's working but that you still have an issue with the coolant levels / air in the coolant.
Top off your coolant, at the radiator, not the overflow bottle, and then bleed it again. There may still be air in the coolant. Bleed it out a couple of two or even three times.
Leaving the radiator cap off, turn on your engine, and loosen the bleeder valve screw. You already know where it is, but to find it, just follow the upper radiator hose to the water neck, there will be a mess of sensors hooked up right after this, the bleeder valve is the 12mm (I think) bolt with a hole in the middle of it. Keep this valve open until pure coolant is spilling out, no air at all, then tighten it down. Top off your coolant again, and run your car for a bit more w/ the valve tightened and the cap down. Repeat a few times until all of the air is out. *don't rev the engine or anything, just let it run.
You can also try screwing in the screw on the fast idle valve... Flat Head, located on top of the Throttle Body.
If the surging stopped once the engine was warm, I'd rule out vacuum leaks. BUT, since it keeps on even after the engine is warm, try the bleeding a couple more times and really let it run clean.
And if that doesn't solve it, then start looking for vacuum leaks like Spiffy said. Spray bottle with water and dish soap works great.
Keep us up to date....
~ josh
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redlude
- Prelude Enthusiast
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I bought the new fast idle valve from the dealership.Also, after the car runs for a few minutes I can put my hand on the bottom of the valve body and I can feel it getting warm.I have bled the cooling system so many time over the past few days, that I have gone through almost 2 gallons of new mixed antifreeze.I just can't see there being any air still in the system.I am going to check one more time for any vaccum leaks , the only other thing I know to do at this point is purchase a new Idle Control Valve(which I really hate to spend so much darn money, and don't know if that will fix it either).. Still open to ideas though.....
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RedRacer
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- Prelude Model: 1995 Si w/mods
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I thought you had already bought the new control valve - I just feel like that's going to solve your problem .....
If you can stand to wait a few days, order it online from Majestic Honda. They're usually much cheaper than a local dealer. Can usually cut the price in half or better.
http://tinyurl.com/yufb68
If you can stand to wait a few days, order it online from Majestic Honda. They're usually much cheaper than a local dealer. Can usually cut the price in half or better.
http://tinyurl.com/yufb68
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spiffyguido
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redlude
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Yes, I was refering to the same one, sorry...I looked at the web site for Majestic Honda, yeah I will hold off, much better price, THANKS..... I think I will try a few more things that i have been reading while I wait. So I will keep everyone up to speed as to my progress.Agian thanks and still open to more ideas..........