When first started my car idles at about 1250 RPM but from there it slowly creeps down to about 700 RPM and stays there. The idle never jumps, just a steady move to the lower idle. Revving the engine doesn't help. Also I notice a slight stall when I hit the gas some times. I changed the air filter about a week ago and cleaned the TB (which wasn't dirty) in hopes of improvement.

Is this normal behavior for an older car or is there something wrong/dirty?

Car: 1998 Honda Accord LX, 160k

 

That's actually normal behavior. Cold idle is supposed to be around 1300 RPM, and warm idle should be about 700. You might be a little low, but it's probably fine.

 

Hi, same thing happens to my car. also an 98 accord LX. I understand cold/fast idle is like 1200rpm and at warm/normal operating temp idle is i believe 750 rpm. However, once in a while the car idle will drop to like something like 300-500 rpm, but never stalls. If, I sit there and wait the idle will go back to the normal 750 rpm. I have checked it with my OBDII No DTC, and I have done regular maintainance. Its got a K&N drop-in filter recently cleaned. New NGK Platinum plugs. 3 Months Old Cap and Rotor (which was replaced hoping to fix the problem). Compression Tests are good. 185psi all 4 cylinders.

Any suggestions to what the problem might be?

 

Have you checked your IACV/EACV? If nothing else, you might want to run some Seafoam through it.

 

Do you know what the IACV is? I have a thread on here of when I fixed on on a Civic. It's really easy to do and afterwards you can just seafoam.

 

I think I am having the same problem ( https://honda-tech.com/forums/honda-accord-1990-2002-2/99-accord-100k-miles-hesitates-rev-up-idle-2761813/ )

First I thought the hesitation occurred only while the engine is warming up but it seems to occur randomly.
After all the maintenance I have done it is now less of a problem. Next items on my todo list are replacing the spark plug wires and checking/cleaning the EGR valve and ports.

As stated before the drop from fast idle on cold startup to normal idle wit engine at operating temperature (750rpm) is normal.