89 Honda Accord Idle problem

I have an 89 Accord with an idle problem. When I start the car up and it is cold it idles fine. As the car warms up the idle keeps going up to about 4,000. This also happens when the air temperature is around 60 and above. I’ve traced out vacuum lines and changed the vacuum box with no change. Also between the valve cover and carb, on the drivers side, there is some sort of air box, if I put my hand over the input side of this air box the idle goes back down. I don’t want to put alot of money in this car but with fuel prices the way they are it would be nice to get back on the road. Thanks

I looked up a vacuum diagram for your car-- what a nightmare! I have the fuel injected version of your car and I thought IT was a rat’s nest of hoses and wires!

Do you have any idea what this box thing is? Are any of the hoses going to it numbered? What exactly is the “input” you’re covering up? Did you have to remove a hose to do that? Any chance we could get a picture? It’s not just the air supply box for the carburetor is it? If it is, then you’re just using your hand for a throttle and that’s a dead end.

A vacuum leak from a damaged hose or a component with a ruptured diaphragm would make the most sense, except usually on a carbureted vehicle a vacuum leak that big will cause the mixture to be overly lean and will cause it to run really rough. When you cover up the input of that airbox thingee, does the throttle physically move at all?

Fwew! Those things can be such a pain in the butt! If you don’t have one already, get yourself a service manual and try to figure out what everything is and what it does. Carbureted cars of this era can be really complicated, but everything works on mostly elementary physics, so there’s nothing you can’t figure out with the right information.

You “don’t want to put a lot of money into the car”. How about something else? How about a repair manual? I’m sure it would tell you what that "thingee" is.

I do have a repair manual and have been all thru it and I am still coming up blank. Yesterday I posted the question out of frustration and left some out.

The “box thing” is the Air suction valve assembly. You referred to an “air supply box”, is this it? On the inlet side of it there is a rubber boot that ties it back into the air cleaner. When the idle goes irradic if I put my hand over that inlet, the idle will drop back down. There is an “air suction valve” that’s part of that assembly but adding vacuum to it manually doesn’t seem to effect the idle.

The manual refers to a high idle valve. Could that be causing the problem? I think it is located behind the carb on the passenger side of the engine.

I will take some pictures and do some more diagnostics today and post them.

Thanks for your help!!

Pictures, or drawings, of the engine bay are hard to come by. At auto zone Web site there are some drawings and instructions for troubleshooting. There are several topics for you to choose from. Click on this link: http://www.autozone.com/az/cds/en_us/0900823d/80/0c/fa/c5/0900823d800cfac5/repairInfoPages.htm In the vacuum diagram section, scroll down to Fig. 24, Fig. 25, and Fig. 26 for your Accord.

Picture 2 shows the engine compartment. The vacuum box I changed out is in the upper left hand corner with the 12 vacuum lines coming out of it. A close up of it in picture 3. Picture 1 shows the air suction valve assembly with my finger pointing to the inlet tube in the lower right corner. I did start the car up and let it warm up and the idle went up. I couldn’t tell if the throttle moved because it is buried under the air cleaner.

Picture 1 doesn’t show your finger pointing. Did you find the vacuum diagrams, and other instructions at the auto zone Web site, helpful?

Wow… that’s a clean engine compartment.

It sounds to me like the vacuum diaphragm that actuates the little valve that lets fresh air into the exhaust manifold has torn, sucking extra air into the intake manifold, causing your high idle. Hopefully you can change just the diaphragm and not the whole assembly-- I think from picture2 it’s that metal thing to the immediate left of the box. Unfortunately this might be something you need to get at the dealer, which might get a little pricey.

Oh, also before you buy anything, double check that all the vacuum hoses are hooked up to the right places and that the hose from the diaphragm to the vacuum control box thing isn’t torn at all.

I did find the vacuum diagrams and thanks for your help. They do a great job of tracing out all the lines, I just need some additional help on what vacuum item could be causing the problem. The second picture is the one that shows just the tip of my finger.