Honda Accord carb high idle probs



I purchase this 1989 accord 2.0 over a year ago and did not do my diligence in regards to condition. Looks great on the inside and starts, says 230k but speedo is not working so not terribly sure how accurate miles are. As mentioned it is carburetor fueled. I disconnected the battery since if I leave it connected it will drain due to alarm feature put on it. It will start ok cold it will be at 2000rpm then steadily climb to 3000rpm. finally today I just jammed the accelerator after it was warm fan on to 5000 rpm and it dropped to 1500rpm still seems too high. I drove it and it just seems to want to climb when not loaded. I have gone over several of the vac lines and they have all the markings of 20 years though they still seem good condition. At first I was worried that some lines were put on incorrectly. I did find #7 where it connects to the back side of the carb pretty dried out and broke when I was tracing it. I have read several high idle probs on this forum and seems like this carb has a normal high idle? About six months ago I took it to a friend of mine who works on cars and he checked the compression, which is good, since there is some oil leaking not sure where from yet.


You need to find a good manual, Haynes, or best the Honda official shop manual. Those carb models ran very well, but are very complicated. Lots and lots of vacuum hoses going in all directions. All the hoses are now old and likely leak, are cracked, and otherwise deteriorated. They need to be replaced and you need a good manual to be sure the hoses are all correctly placed. Your symptoms could easily be a misplaced vacuum line, but which one?


Odds are this is a simple fix. It’s related to the choke, choke linkage, fast idle and/or idle speed screws, or possibly the carburetor secondary linkage.

It should idle about 1500 or so RPM when the engine and choke is cold but not at 3000 or whatever.

Without carburetor in hand I can’t tell you exactly where the problem lies and can only say this should not be a complicated issue.
If the car has had this problem since you bought it there’s always the possibility that someone in the past has dinked around with various adjustments while trying to override an anti-diesel solenoid problem on the carburetor.
When the solenoid is not operating (no power or bad part) the idle circuit is closed off and someone who is not familiar with this will screw things around in an effort to make up for it.


By this time, all of Honda’s competitors had switched to fuel injection. Honda was embroiled in a major dispute with Bosch over paying royalties to use the Bosch injection system…They continued to use a HOPELESSLY complex feedback carburetor. Good Luck…


I would reiterate that you need to get a manual for this thing. The idle air control system on these is a very strange collection of solenoids and thermal valves-- it’s not at all like either an older carburetor or a fuel injected car. It’s not terribly difficult to figure out, but it is unusual.

The idle should be around 850 (or whatever the sticker says under the hood), so at idling at 1500 is too high (although so many of these are driving around with idle issues that perhaps 1,500 is “normal” these days).


I think Honda pretty much set the standard for use of countless solenoids and rolls of vacuum tubing.


Hmm? They made plenty of these with fuel injection (I drive an '86 with FI), and it uses the PGM-FI system which is not a Bosch design. And furthermore, Toyota and Subaru (to name a couple) still sold carb’ed cars in '89 and the other carmakers had only made FI standard in the last year or two. And a lot of those went to single-point injection which wasn’t much better. So I don’t think it’s really accurate to say that Honda was wildly behind the curve here.

I do agree that like most later carbed cars they were pretty complicated, but not impossible to keep running well. They are overall quite nice little cars really.


Wow! many thanks to all those that have participated in my question. ok4450 you have mentioned something that happens. If it is at high idle when I shut the engine down. It will diesel pretty bad. If I can get it down to 1500 it has a slight diesel. I am hopeful that it is going to be something simple but can get overwhelmed with the vac hose thing since it is so tight in the backside next to the firewall.
So far from what I have read here and from others is I should just replace all the vacuum hoses…oh what fun, or I have heard mention from others maybe not here to replace the carb or rebuild it. If I replace the vac lines then I will learn all the places to hook it up it I end up replacing it: I started my 12hr shifts for the next four days so won’t be able to spend a whole lot of time until Sunday.