1991 Honda Accord idealing to low

Hi nidal_2,

Did you clean the throttle body and idle adjust screw before setting the idling speed?

Does turning the idle adjust screw increase the idling speed?

Does idling speed decreases when the A/C is turned on?

Have you checked the valve clearances?

Was the IAC replaced new or used?

Are there any trouble codes?

thank you for the fast assistance,
no ididn't clean the throtle body nor the adjust screw.the idle adjust screw will increase the idling speed but as i told you it will drop again after some time and it is more rough when i put on the AC. the iac was replaced used and i didn't check the valve clearences however i'm hearing a little valve knock after accelerating over 3000rpm. when ever i'm driving up a hill. i would appreciate any diagrams on cleaning the throtle body.
thanks

There are no diagrams to show you.

Remove the air cleaner hose and spray some carb cleaner into it. Use a rag to scrub the inner port with throttle plate opened fully.

Remove the idle adjust screw on top of throttle body. Spray carb cleaner into the idle adjust port and allow to soak for a few minutes.

Clean the idle adjust screw and reinstall. Turn screw fully in and back out 1/2 to 3/4 turn.

Start engine and allow to warm up and readjust idle speed if necessary. Engine might require some cranking time due to the presence of carb cleaner.

Hello
i cleaned the throtle body and till now it appears to be working fine but i found to the left side of the battery a broken hose from a plastic black 10cm*5cm box which has some kind of valve with a 2 wires connector i fixed it i am wondering would this have anything to do with the problem.
thanks.

Any vacuum leakage would increase the idling speed and not decrease it.

The black box and solenoid that you are referring to must be the air resonator solenoid control valve. It is for reducing resonance noise and is not related to the idling speed.

hello,
it seems that the same symptom is back but not as rough as before no error codes any suggestions by the way recently i changed the 2 timming belts and all the seals and after starting the car every thing is ok but when ever i accelerate i hear a humming like sound and when releasing the sound will go any suggestions

Check the drive belt tension. If they are adjusted too tight, they can cause humming noises.

As to the erratic idling, when replacing the timing, were the valve clearances checked/adjusted?

Did you clean the IAC before installation?

hello,
i didn't check the valve clearance but the problem of erratic idling was before i changed the timming belts and the iac was cleaned by the way yesterday i removed the two wire connector to check the idle speed i found that it was again below 500rpm i disconected the hose going to the black box i reffered to before the idle speed will rize the hose connected to it has the no 8 written on it plz advise