I have an 89 Accord with a high idle problem. I pulled into the drive several weeks ago, shut the car off, it dieseled then died. I started it right away and it idled about 4000 rpm without dropping. After looking for the obvious (gummed up/stuck throttle cable, loose vacuum line…)and finding nothing. I was told to change the vacuum box in the passengers corner of the engine compartment. No change… I then changed the idle mixture valve assembly that is located by the valve cover. No change… Any help would be appreciated. Thanks
Much could depend on which model you have. Some were fuel injected and some were carbureted, with about a 50/50 split on them.
If I assume you have the carbed one based on the symptoms, then a choke flap not opening all the way or hanging fast idle linkage would be the main suspects.
If it’s an injected vehicle then you may have an Idle Air control valve problem.
It is a carbureted car. If I take the air cleaner cover off there is a port that goes to the idle mixture valve. If I put my finger over that hole the idle will drop to 1500 to 2000. As soon as I take my finger off the idle goes right back up to 4000.
It’s been a couple of years since I’ve messed with a Honda carb so I’m having trouble picturing what you’re talking about.
Which idle mix valve is this and are you sure this is the proper term? Any way of posting a pic?
Even 1500 rpm is way too high.
The first thing I would do is take off more of the air cleaner housing and hose the carburator with carb cleaner. Concentrate on the linkages. It is cheap, easy and might do the trick.