High Idle 2500rpm and won't come down!

[TNTumbler]

OK, I'm getting sick of this issue and quickly. I've gone through EVERYTHING on this website and the manual to try and figure out what is causing it to idle at 2500RPM and not come down. I've replaced the vacuum lines, I've shot carb and choke cleaner through it, I've swapped out the carb (the carb I put on it wouldn't idle at all!) and back again, and I'm just quickly getting fed up with it. I called Honda and several local shops around here. No matter who I called said it was going to cost between $900 to $1500.00 to get it right (doesn't matter if its to rebuild the Carburetor or Replace it). I'm almost to the point where I want to sell it and just be done with it. I'm getting to old to be under the hood every single day or weekend trying to fix this car's issues one right after the other. This is the last thing that's getting to me and I just can't seem to get it to run right! What do you think? OH BTW: It was doing this once before, but it stopped and ran fine after I changed the PCV Valve, done that again, and this time it didn't fix the problem. Also there is NO Check Engine Light on on the dash. So, I'm stumped.

Replaced so far:

Vacuum lines (every last one of them)
Idle Kick Down Sensor
Cold Air Sensor
Got a carb from the junkyard and rebuilt it (it won't idle with this carb, adjusted the idle backwards and forwards, just won't idle)
Fuel Filters
Fuel Lines

Also Choke is fine, checked, tested, cleaned

If I can't sort this out, I'm going to just sell the car and move on to something else. I bought this car to be a show car, but I'm tired of it trying to show me who's the boss and it showing it's ass.

[g.frost]

Check high idle unloader and associated vacuum circuit?

[cygnus x-1]

It sounds like something is leaking air into the manifold. I would try systematically checking every vacuum line that is connected to the manifold. One at a time, disconnect each line to the manifold and plug the line and port to see if it changes the idle. Hopefully you will find one that brings the idle down and then you can trace it back to whatever that line is connected to.

C|

[Dr_Snooz]

What is the condition of the throttle cable?

[TNTumbler]

Dr S the throttle cable is brand new from Honda (previous one snapped not long after getting it home). I used the original to figure out where it needs to sit like the old one. I'm going to change out the carburetor with a freshly rebuilt one I got for $27 bux from a friend (also gave him one I got that needs rebuilt in the trade off). Hope this solves the issue. I'm just running out of ideas of what could be causing this issue. I've replaced just about everything I can to prevent or solve vacuum leaks.

[g.frost]

.... In addition to the fast idle unloader test (per the service manual)..., If Thermovalve A is not closing when the coolant warms up, this will cause the high idle to hang (these thermovalves get erratic with age...). Test with a vacuum pump/gauge is to disconnect the high idle unloader vac line and pump it down to vac: does it hold vac and does the high idle cam drop out?

The test procedure is described on 11-29 of the '88 service manual available for download.

[g.frost]

"Replaced Idle Kick Down Sensor" ? Must be thinking of a different car. No such thing on the 3g.

[TNTumbler]

The 1986-89 Honda Accord has a Idle Kick Down Sensor aka Idle Stop Solenoid on them. It is in the back of the carburetor and held in via a 8mm bolt/screw.



Idle Stop Solenoid | 1989 Honda Accord 4 Cylinders 2.0L 2BL SOHC | AutoZone.com

Another website I looked at called it a Idle Kick Down Sensor. Other places call it a Idle Stop Solenoid. Sorry, my bad! Sheesh.

[g.frost]

Do yourself a huge favor and download the Honda service manual(it's FREE): Primary Slow Mixture Cut-Off Solenoid Valve.
Not likely at all to cause the fast idle to hang at 2500 rpm. Did you test the fast idle unloader functon and thermovalve A? Just need a vacuum gauge/pump and follow the service manual procedure. This problem is very common on these old carb engines. None of these components are internal to the carb.
...knock on wood; my carb has never been opened up, but I did have this very problem you describe.


Service Manual Here: https://www.3geez.com/forum/technical...l-updated.html

[TNTumbler]

I downloaded the manual, took the carburetor this morning to a friend who works on 1950's and 1960's cars. He opened up. Float - Fine, Jets - Fine, ALL VACUUM PORTS - Fine! Replaced gaskets, and sealed back up. So, carb I got from the salvage yard yesterday (car was a manual but has an automatic carb on it) after switching the A/C vacuum diaphragm from two ports to one in the end didn't work. It idles at 3500rpms but it tested fine when checked also. SO! He came over checked all vacuum lines under the hood and his only conclusion is the car is cursed. He can't find anything wrong, I can't find anything wrong, so, I'm just ready to just get rid of the headache and move on. Everyone tells me to install a Weber carburetor, but no one is willing to help buy the thing (my birthday is next month) and fail to realize I'm working on a VERY LIMITED budget! End of story, enough said, I am DONE!

[g.frost]

This high idle hang after warm up is so common on the 3g carb. I thought to put together a simplified test and bit of 'Theory of operation' to get started on figuring out what's wrong with your carb. Please download and refer to the service manual to see what and where all the referenced components are.

The first thing to check is to make sure the choke opener and fast idle unloader vacuum circuit is working. This is because, .... that's what controls the high idle when cold. When it fails, the high idle hangs on after warm up.

A Vacuum Gauge/Pump is required to test for leaks and proper functions. It is essential to have this diagnostic tool to work on the vacuum system in these cars! They are available at auto parts stores. Rent, borrow, or buy. I got a cheap one for $25 and it works fine.

Start at the Choke Opener, it has 2 vac lines attached #26 goes to the 'black box': Cranking Leak Solenoid.
This valve opens when the key is in the 'cranking' position. It keeps the choke closed while starting. It closes as soon as you relase the key/stop cranking, allowing vacuum to pull the choke open. With the engine off, check this line to the black box with the gauge: unplug from the choke opener and make sure when you pump it down and it holds vacuum. Ok?, no vac leak there.

The other Vac line from the choke opener is #18. This goes to Thermovalve A, and to one of the ports on the Fast Idle Unloader. Notice Thermovalve A (look at the vac diagram in the manual to see what I'm writing about) has 3 ports. One is line 17: this is a 'vent line' it goes to the bottom of the air filter box to supply clean ATM air for 'leak back'. When thermovalve A is cold , it opens line 17 to 18 and 19; they are at atm, These control the 2 stages of high idle when the engine is cold. 18 to the choke opener: It is the choke opener that supplies vacuum to this circuit; look closely at the vac diagram, a vac port goes directly into the carb where the choke opener is attached.

I recommend to follow the service manual for testing, but I'll go ahead & (try to) 'simplify' some here....

With the engine cold. ( coolant below 57F) the choke should completely close when tapping the gas peddle. (engine off)
Now crank and start, the choke should quickly move to the 'half choke' position. Thermo valve A is open and letting air leak into the lines 18 and 19, keeping the fast idle cam at what should be around 2000rpm when cold.

As soon as the coolant starts to warm the 'first stage' on thermovalve A closes and line 18 is allowd to pull down vacuum. (it's isolated from line 17) This lets the idle drop to around 1300-1500rpm and lets the choke fully open, butterfly straight verticle. Vac line 18 goes to the 2 stage fast idle unloader, pulls the cam to lower the idle.

As coolant further warms, thermovalve A fully closes and allows vacuum to line 19 to the fast idle unloader. This drops the idle from 1500 to the fully warmed up idle, around 800rpm. The fast idle unloader is fully dis-engaged now.

Let the engine fully warm up, (....racing away at 2500rpm....?) Verify; does the choke go to vertical position?
Now, where is the leak...? Start with the choke opener, unplug 26, hook your gauge to that port on the choke opener. It should pull vacuum. No? is the leak in the choke opener or line 18? unhook line 18 and cap it at the choke opener port. Does the choke opener pull vacuum now? No: vac leak is most likely in the choke opener. Yes: leak is 'downstream' in line 18: thermovalve A or fast idle unloader.

Put vacuum gauge on the line 18 to fast idle unloader and pump it down. Does the idle drop? Does this line hold vacuum (it should when warmed up) If not, you can test thermovalve A by capping the port 17 on it to block the leak back line. Does line 18 hold a vacuum now? Does the fast idle drop now? YES: replace thermovalve A. No: leak must be in the fast idle unloader section. ...

If the fast idle unloader now appears to be the problem, test the ports on it directly: they should hold vac when pumped down and should dis-engage the fast idle cam: verify/test this function...

Edit to add: note that #19 also goes to charcoal canister purge; check this pumps down, holds vac as well.

[TNTumbler]

I downloaded the manual, took the carburetor this morning to a friend who works on 1950's and 1960's cars. He opened up. Float - fine, jets - fine, all vacuum ports - fine! He came over checked all vacuum lines under the hood and his only conclusion is the car is cursed. he can't find anything wrong, i can't find anything wrong,

please read revised edition.

[g.frost]

Something has to be holding one of the throttle valves partly open to 'idle' at 3500rpm; sounds like this other carb you put on has put you another 1000rpm away from idle.

Did he put a vacuum gauge on the exact ports I mentioned to test them specifically? Did you see him perform these specific tests with a vacuum gauge?

[g.frost]

That's a nice looking car you have there. It puts my cream-puff beater to shame.
I really should scrape the barnacles off. Jimmy (my daughter named it) can get temperamental if he doesn't feel loved.


.

[Oldblueaccord]

What is the condition of the throttle cable?

Can we get this moved over to the for sale section.

[TNTumbler]

OldBlue I'm seriously thinking of selling this car since it obviously hates me to the core, BUT I won't let it go easy or cheap! I have sank WAY too much money into it. I put the other carburetor back on (the original carb the car came with) and now the battery is dead. I'll get up early and jump start it (again! Security where I live admitted opening the door to see what was in the seat and didn't shut the door all the way). G.Frost I checked them first and my friend went behind me (me standing right there) and checked them with another tester. We even went as far as to check other vacuum lines comings and goings to check for carbon build up. Everything is fine. So, this leaves only one conclusion (and several members of the car club have mentioned this too) is to change the carburetor over to a Weber System and do a Vac Delete under the hood. I really hate to do such as it would take away from the OEM look that I'm so hard at trying to keep. So I dunno. I think I know why the other carb ran at 3500rpm as it is a carburetor for an Automatic Transmission and my car is a manual shift model. Someone told me that this wouldn't work, but I'm hard headed and the only differences I saw besides the throttle had an extra piece on it, and the A/C Vacuum Diaphragm had two lines and mine has one. So, I dunno if there might be something else I'm missing.

[Dr_Snooz]

Check your throttle cable again. If it's kinked or at an odd angle, it will hang up and cause exactly the symptom you describe. With all due respect to your buddy, these carbs have almost nothing in common with the carbs he knows. He might be awesome, but he doesn't have anything to offer you. If it isn't your throttle cable, then it will likely be one of the dash pots, vacuum actuators or electric solenoids that have been attached to the outside of the carb. Their operations are detailed in the manual, along with extensive troubleshooting instructions.

I know the misery you're experiencing, and I can tell the car is getting to you. Take a break; take a walk and get your head clear. Then come back and fix the car. You can do it and it won't be expensive when you find it.

[TNTumbler]

Thanx Dr_S. My friend restores 1950's and 1960's automobiles, but he has been working on all kinds of cars since he was 13 yrs old (he's now 51). He used to own a 1988 DX Hatch and he said his gave him a fit and he showed it who's boss by ripping the "Vac Crap" out of it and replaced it with a Weber. I'm trying to get this dang car road ready before April 5th and yes its getting to me as I've done nothing but fight this car since I bought it. It breaking down in Forrest City, AR on the way home should have been the first sign of trouble. I fix one thing and something else comes unglued and this continuous cycle is getting rather annoying quickly.

[g.frost]

Hope you can get the high idle problem sorted out. It just has to be something holding the throttle valve open. ...check the secondary too. (Hard to imagine that a 'vacuum leak' would allow enough gas to keep the idle to 2500+ Rpm without gas from the throttle)

In CA, there is no option to replace the original carb; to pass smog. Mine has been almost completely trouble free for 164K, 26 years and has always passed smog by a mile. (less than 1/10 allowable emissions)
The only issue I've had with it was the choke opener diaphragm leak, causing the high idle hang. (just like your problem)
At the time (a few years ago) I had to replace thermovalve C, choke opener, and intake air control diaphragm(leak).That's all the 'carb' has needed in 26 years. I know these don't get much 'respect' around here, but I'm stuck with it and it has served me well, no complaint. These issues had me perplexed until I spent enough hours with the service manual, and a few more with my poor back hunched under the hood. When it is working right, the idle is very smooth and the gas mileage is great too. 34-36mpg hwy, (26-28 city.)

The only time this car has ever left me on the side of the road (...well once I ran out of gas.) the fuel pump quit. This was early failure, like '95 or so. It has been one of the most reliable cars I've owned.

[Oldblueaccord]

OldBlue I'm seriously thinking of selling this car since it obviously hates me to the core, BUT I won't let it go easy or cheap! I have sank WAY too much money into it. I put the other carburetor back on (the original carb the car came with) and now the battery is dead. I'll get up early and jump start it (again! Security where I live admitted opening the door to see what was in the seat and didn't shut the door all the way). G.Frost I checked them first and my friend went behind me (me standing right there) and checked them with another tester. We even went as far as to check other vacuum lines comings and goings to check for carbon build up. Everything is fine. So, this leaves only one conclusion (and several members of the car club have mentioned this too) is to change the carburetor over to a Weber System and do a Vac Delete under the hood. I really hate to do such as it would take away from the OEM look that I'm so hard at trying to keep. So I dunno. I think I know why the other carb ran at 3500rpm as it is a carburetor for an Automatic Transmission and my car is a manual shift model. Someone told me that this wouldn't work, but I'm hard headed and the only differences I saw besides the throttle had an extra piece on it, and the A/C Vacuum Diaphragm had two lines and mine has one. So, I dunno if there might be something else I'm missing.

Take the throttle cable completely off the carb to rule it out. With the motor OFF. move the throttle by hand and see what it feels like. Your looking for the throttle blades hanging sticking on the gasket they need to be shut at idle. Look down the carb with a flashlight and confirm this.

Just because someone works on 50 and 60 cars doesn't mean he's a carb expert. "rebuilding" a carb is more then just changing gaskets no matter how easy it sounds on the internet. Most carb rebuild kits come with so many wrong pieces for the carb your working on its not even funny.

[Dr_Snooz]

Just because someone works on 50 and 60 cars doesn't mean he's a carb expert.

Especially when he's unsuccessful with the carb in question.

I've rebuilt two Keihin carbs on my '76 and '82 Accords. The first rebuild was an unmitigated disaster and I had to throw the carb away. I couldn't salvage it. The second rebuild was very successful and worked well until I sold the car. I can say with certainty that the Keihin carbs bear no resemblance to the Edelbrock on my truck. They are completely different animals. Just because I can rebuild the Edelbrock doesn't mean I know squat about the Keihin.

Bear in mind that you're working with a classic car that you want to show. Most guys in your situation would send the car away to a restorer and dump $20k+ into it and receive back a completely new car. You're trying to do a resto on the cheap, which is great, but what you lack in funds you'll have to replace with patience, persistence, research and cleverness. You're in the middle of a work-out period where everything that was marginal breaks. If you work through it, you'll be rewarded.

[Oldblueaccord]

Especially when he's unsuccessful with the carb in question.

I've rebuilt two Keihin carbs on my '76 and '82 Accords. The first rebuild was an unmitigated disaster and I had to throw the carb away. I couldn't salvage it. The second rebuild was very successful and worked well until I sold the car. I can say with certainty that the Keihin carbs bear no resemblance to the Edelbrock on my truck. They are completely different animals. Just because I can rebuild the Edelbrock doesn't mean I know squat about the Keihin.

Bear in mind that you're working with a classic car that you want to show. Most guys in your situation would send the car away to a restorer and dump $20k+ into it and receive back a completely new car. You're trying to do a resto on the cheap, which is great, but what you lack in funds you'll have to replace with patience, persistence, research and cleverness. You're in the middle of a work-out period where everything that was marginal breaks. If you work through it, you'll be rewarded.

Well my fix for carbs is take out old carb,drop in 5 gallon pail with the other junk carbs,put new carb in its place. And i mean new not a rebuild from autozone. I dont think you can get real "carb soak" that works anymore to even clean one.

[g.frost]

The carb is just the carb though, it has never actually given me any problems :::: It is the litany of $hit that is strung at the end of those miles of vac tube; The frequency solenoid valves, air suction, air leak, anti-afterburner, feedback control solenoid, fast idle unloader, throttle controller, bla bla bla there's plenty more. A Vacuum Spaghetti Logic nightmare of parts that are mostly now discontinued. Never an error code from this 'computer' either, and so much fun to wade through to try & diagnose a problem. These are the things that I'm afraid will eventually permanently park my car.... What were those engineers thinking? ....never mind, I already know; I've seen it first hand.

My engine is solid, strong, burns no oil, no blow by, and runs great for now ......knock on wood. Keep running Jimmy.

[TNTumbler]

Well, I went and got a carb from the salvage yard (AGAIN!) and this time the guy drove the car from the "WAITING LOT" to the doors where you enter the yard from the cashier stations. It purred like a kitten at 750+/- rpm. So we pulled that carburetor and brought it home. Put that carburetor on the car, got everything hooked up like it should be, and NOTHING! The carb puked gas on the ground under the car, didn't want to run, let alone idle, and puffed fuel smoke as it flooded out. I'm like WTH? closed the hood, walked away, and gave up. I honestly think the car hates my guts and a lemon to boot. So, I listed her on Craigstlist as I've pulled my back out, landed in the ER from a torn rotator cuff, and just honestly have had enough. I have worked on Hondas (fixed three this past week with success), worked FOR Honda, and this is the first one to EVER stump me as I can't figure out what the hell is its problem.

[g.frost]

Wow, the salvage yard had a perfectly running, drivable 3g, and they let you take the carb off it?
A gross raw fuel leak to the ground should be easy to find the source. Maybe the float valve got stuck when transporting it.
Hope you got some good pain med for your rotator cuff and are feeling better.