Yet another high idle thread

[KillHirro]

Hello all, first time posting but I've been lurking around trying to find a solution to the problem on my third generation accord.

First and foremost, it is a 1989 Honda Accord LX 5 Speed. The car has just over 160,000 mi and I am not the first owner, somebody sold it to me after it was impounded for not being registered. When it was sold to me, the idle liked to sit at 2500+ and would slowly raise up. I have viewed just about every dhigh idle thread and tried solutions listed by some very helpful people (oldblueaccord, Dr. Snooz...) but the issue still persists.

So far, here is what I have replaced:

- Oil Change
- Fuel Filters
- PCV valve
- (I didn't do it but they appear to be (uncracked) quite new, no more than 5 years old) Vacuum lines and vacuum control box insides
- Carburetor needle & seat

After replacing all these parts, there has been no change whatsoever. The idle likes to sit at about 2100 - 2300 when first starting and just won't back down after that. A couple things I have noticed are:

- The cooling fans don't turn on, no matter how long I leave the car on.
- The engine likes to diesel slightly (less than 2 seconds) after the car has been turned off
- There is a gasoline smell around the car while it is on (no leaks, I have checked all the fuel lines)
- The choke doesn't open all the way as the car is warming up (I have checked the choke opener diaphragm and there is a hole in it, but this wouldn't be causing the high idle, right?)
- While the car is running I took a peek under the choke and it appears that the lower chokes are not opening.
- I have checked the dashpot system and it all seems to be good and functioning.
- I have tried spraying carb cleaner on just about every square inch of vacuum hosing and it results in no change in idle.

I can take pictures of anything that may be needed to help assist in the repair of this car. The interior is a solid 9.5/10 so I have been trying to restore it to be good as new, I don't want the car to end up in the crusher..

[Howlite]

It could be your fast idle staying on, did you check both thermovalve A and thermlvalve B
They are under the carb next to the firewall mounted on the intake manifold, they should have two or three vacuum lines attached.

Also, is the coolant not getting hot? Check if the thermostat closes.

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[KillHirro]

Thank you, I will attempt those first thing after work tomorrow, I'll update on how it goes.

[Oldblueaccord]

Just to add make sure the actually throttle cable is not tight at idle. Some jokers adjust everything from there.

[KillHirro]

Ok, I checked thermovalve A but I didn’t have enough time to find/check B. When I “checked” A it was just a visual inspection and tried to turn it out of its socket, which it didn’t budge.

I also checked the throttle cable and adjusted it to spec (~2mm of play) and it it not pulling on the throttle plate at all.

About the coolant thermometer, I didn’t get to check the insides quite yet, but upon inspection of my coolant levels inside the radiator, i noticed some rust around the opening, like someone put water in it a while ago.

In addition, a nice fellow happened to walk by as I was doing my inspections, and he mentioned how he owned the exact same car and model, carb’d n everything. He told me to do a complete coolant flush first, make sure my timing belt is A ok, and then go about trying to fix other things.

When I have time maybe tomorrow I will inspect the coolant thermometer and update on how that goes. Slight chance it’ll be next week since I will be going backpacking this weekend.


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[ShiRen]

Have you tried just turning the idle knob down?

Also, you mentioned looking under the choke, it should be open when it's warm. And there's no lower choke, those are the throttle blades

[KillHirro]

Okay so here’s what I’ve done so far:

- My coolant is getting hot, so the thermostat is working (or stuck open, i’ll find out this weekend when I get to it)
- Adjusted the throttle stop screw, it’s backed out all the way for now
- Adjusted all the other diaphragm screws and backed them out all the way
- Sprayed carb cleaner everywhere, for both cleaning and to check for other vacuum leaks (couldn’t find any)
- The one leak I found was the diaphragm of the choke opener


Some more things to note:

- I know I have a bad alternator and already have a replacement, just need to install it.
- The engine/car is very shaky/rattly when the engine is below 2000 rpm
- 4th and 5th gear are shaky only when throttle is applied
- Even with the choke almost closed the idle is still high

What I’m planning on doing:

- Vacuum testing both thermovalve A and B
- Taking a peek at the coolant thermostat when the car is cold
- Complete coolant flush

Anything else I should add to the list? And thank you guys for your help thus far

Video of engine running: https://youtu.be/st2lu6-8Yc4

Black Box Insides


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[KillHirro]

Here's what I did:
- Complete coolant system flush
- Tested thermovalve A
- Tested power valve
- Ziptied choke open

What I discovered:
- Coolant had not been changed for years
- Thermovalve A was dysfunctional
- Power valve did not make a clicking sound as the manual stated (the solution is to replace the carburetor)

Moving forward:

I just bit the bullet and bought a weber. It is a 32/36 kit that bolts right on, from eBay. I plan on going through all of the Weber conversion forums to get a good knowledge on any issues I might run into on the way. I already have a fuel gauge and fuel pressure regulator on the way as well. When I replace the carb I plan on doing the alternator as well, so hopefully after everything is installed she'll start right up.. then I can start working on the stuff I really wanna do.

If anyone has some wisdom they'd like to share about the swap, It would not go unappreciated.

[KillHirro]

Funny little update:
I was getting kinda impatient waiting for my Weber to arrive and I really wanted the problem fixed on this darn Accord..
Basically, I rechecked for vacuum leaks and found one at the front base of the carburetor, where it links onto the intake man.
Right before this, when the car was off is when I noticed the secondary throttle blade ever so slightly open. To my knowledge, these aren't supposed to open at all unless WOT, so with a little (a lot) carb cleaner and some silicon lubricant along with some extraneous cleaning of the springs and linkages, I was able to fix my high idle.

So basically a kinda large problem was solved with very cheap things. I just thought I'd share just in case someone else runs into this problem.