Idle problem Can someone please give me some advice...my 87 honda is automatic and it idles high when in park and when I hit around 50mph it gets sluggish by kicking back into a lower gear.

Hi. Thanks for your question. For information on honda dio 3 you can also visit https://www.reliable-store.com and download the entire workshop manual which includes all the information along with the diagrams for better understanding. Good day!

this may help:
2003 Mazda Protege is stuck in park Brakes Transmission Automatic Engine...

some cars may have interlock with the brake switch to the shift lever inter-lock. have someone step on the brake, if brake light won't come on, suspect the brake switch is preventing the shift.

go to an auto parts store that will give Free trouble code scan

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Sounds like a possible vacuum leak Julie. Spray some carb/throttle body cleaner around the intake tubes/manifold while engine is running. If it sucks it in and the engine responds, you have a leak. Or you could have another idle control issue. Check (or have someone check) the vacuum leaks. If ok, post back and I will give some other things to check.

check for vacuum leaks on hoses and connections as well as check intake gasket for leak by spraying carb cleaner around the gasket mating area,if rpm changes then that is where the leak is.

It may be caused by a vacuum leak, make sure to check all your hose for cracks and/or hoses that may have popped off

Try changing your idle control valve, that should do the trick!

it sounds like it is slipping. What I mean by this is, if it is a manual transmission, your clutch may be shot and need to be replaced. If its an automatic transmission you might have problems within the tranny. I do not know anything about automatics so I couldn't help you there

if its a carb model you might need to strip and refurb the carb if not buy a second hand one they are pretty cheap or it could be a choke problem

I have an 87 Accord with fuel injection that always had a fast idle, and a surging problem when warming up. Both problems went away when I replaced the fast idle valve, which is bolted to the rear of the intake manifold just downstream of the throttle body.