1989 Accord high idle and dieseling

For the last few months my car has had erratic idling and horrible dieseling problems. Initially, the car would idle so low that I would have to keep my foot on the gas pedal while at stop lights to prevent it from dying, ever time I turned the engine off it would diesel out. In the last month the problems have morphed into a constant high idle (~3000-4000 RPM) and dieseling to no end, probably due to high angular momentum. The car runs at normal temp, I?ve cleaned the carb and links, and adjusted almost everything that can be adjusted on the carb to lower the idle but nothing has changed. Need some help before I have to take out a loan to pay for the wasted gas, thanks. (carb, manual, ~120k miles)

Check the electrical connections to the choke first . . . they corrode and get dirty and will cause the choke to malfunction, eventually the idle will race way up and you could have damage. The carb on my 89 started acting up like this and I had problems until I changed it. I had high idle. low idle, stalling, hard starts, dieseling, and so forth. I checked every wire, every vacuum hose, everything I could. I’d try the choke first . . also all connectors and hoses . . . then get back to us here. Rocketman

Hey Rocketman, Sorry to be the village idiot here but what is “dieseling” ?


A failure to idle usually points to one of 3 things; a vacuum leak, blockage in an idle circuit or carburetor air bleed, or the failure of the anti-diesel solenoid on the carb.
It’s going to be hard to tell you what to do here since you’ve done a lot of adjusting in an attempt to repair the low idle.

The first step is making sure that power is provided to the anti-diesel solenoid and that the solenoid is operative.
This solenoid is a small electrical widget mounted on the front of the carb. With the key in the RUN position verify that you have power provided to that solenoid. If you do, and with the key still on, connect and disconnect the solenoid several times. You should hear it click each time you connect it.
If you do, then the solenoid part of the idle circuit is good and you then have to consider tearing into the carb or using one of several “shade tree” methods of hopefully cleaning the problem out.

If you have no power at that anti-diesel solenoid then check all of the fuses. If there is power provided to the solenoid and there is no click then the solenoid is defective.
When these solenoids are not working for whatever reason the engine will not want to idle because the solenoid needle (which is spring loaded to the closed position) shuts off the idle circuit internally in the carburetor.

Hi Jeff! Dieseling is when you shut the key off but the car continues to run . . kind of run, anyway. Didja see National Lampoon Vacation? When Clark brought the new car hone, he shut it off but it continued to run . . but sounded like a diesel engine, knocking and rocking, banging and running rough. Easily cured with a manual tranny by putting the car in gear. How’s the Accord? Rocketman

Thanks for advice, I’ve checked the wiring and it all seems clean and well connected. Any other ideas?

Still in one piece. I’m going to look for a “newer” one when I get closer to graduating college (99-01 model). Sometimes it will run momentarily when I shut the key off if it’s cold and idling really high. I don’t know if that counts.

throttle plate in the base of the carb could be sticking open a little bit, you have to get the breather off and then hold back the upper throttle cable link to be able to twist the throttle plate/lower linkage to feel for gritty places. Berrymans B-12 works great for blasting away the crud, but the bushings on either side of the carb body could be worn out.
Vacum advance on the dist body might also be a problem. And you should check the choke pull off diaphram that controls the top plate of the carb.

I’d try OK’s solenoid solution . . at least for the dieseling. I looked at mine and it seems easy to get at. The Chiltons I have seem to suggest an air intake leak or vacuum leak for the high idle. I remember MY high idle was due to a dirty connection to the electric choke . . . check if there is current coming to the choke AND the solenoid as OK suggested. I betcha I can get a part # on it (from my 89) if you want to change it (the choke or the solenoid). Rocketman

Good post. Those choke connections are vital.

Thanks for all the great suggestions:) I’ll be out of town until the 27th so I won’t be able to provide an update till around then. Sounds like Jeff and I are in the same finical abyss that is college, whatever work I can do on the car myself (without creating more work that is) will save me a bundle! Thanks and I’ll back to you all as soon as I can.

I have a '99 Mazda Protege that had horrible erratic idle and also had to keep inching up at red lights to keep my car from killing. My issue ended up being a dry-rotted air intake hose that had a crack in it. New air intake hose on it now and the idle problem is no more. Don’t know if this might be related, but I thought I’d mention it just in case.