I've got a 1985 Accord, 1.8L?, 4cyl, 12 valve. When I turn on the AC compressor, the engine revs up to the red line if I let it. When I click off the AC, it immediately goes back to normal idle. Any ideas??? I'm new at this, so be gentle. Thanks!!!!!

 

sounds like a relay or vacum relay of some sort.... I would look for loose or cracked/broken vacuum hoses to start with... Is everything else in the car acting normal and working ok? Has this ever worked before?

 

ok so when the car is idling normally the idle is set to have the engine run at a certain rpm. when you turn on the compressor, there is an extra drag on the motor and if this wasnt compensated for, the motor would probably stall. so there is a system that engages to increase the rpm a little to compensate for the extra drag. i like the idea of it maybe being a hose but i just dont know that much about those old hondas.

 

I mentioned a hose or vacuum line based on some prior issues I've seen with 81 Chevy Citation's.... I don't know if it still applies but a few times when I had weird issues it was a hose going to the carb..... I would start with everything connected to the carb, trace them back to their source and make sure that they are connected and not dry rotted or broken. Then look for missing hoses/un-plugged items that are supposed to be capped.... Then I'd check everything around the distributor.... Hope that adds a little light.... Be sure you post the fix on here when you get it fixed if you could! Thanks

 

I haven't had a lot of time to play with this problem. I just don't turn on the AC. I found two valves that should control the increase in idle to compensate for the AC being on. I have tried disconnecting both (seperately and collectively) and also just disconnecting their vacumn lines and jumping out their vacumn lines. None of these have made any difference. If the compressor turns on legally, the engine revs up to the red line. If the car is in gear, of course, that means that you have to stand on the brakes to keep control. The car seems to run and idle fine otherwise. There is a little power loss after the car reaches operating temp. If you are idling and temp starts to climb, the fans turn on and the RPM drops about 100 RPM, as soon as the fans cut off, the RPM goes back to normal. I don't htink this has any bearing on the problem. How exactly does the throttle open when the AC goes on??? I can't see any solenoid or anything that seems to be causing the increase in RPM. I appreciate your posts and hope to be able to resolve this problem soon.

 

there is an adjustment screw ,, if you look at the carb from the frt of the car , the screw is on the left side , frt side of carb .. there is an a/c idle up diaphram, make sure the linkage is not bent or hanging up,, if linkage is ok, turn the screw counterclock wise,, i bet someone tought it was an idle adjustment ,