I just bought a 92 Si 5 speed and it has a rough idle problem. If I rev it to about 1000 it smoothes out and rund perfect. Below that it's pretty bad. I have changed the plugs, checked the wires, changed cap and rotor. I need some suggestions on what to look for next. I would appreciate as much help as possible since this is my first Honda I have owned and want it to be a pleasant experience.

Thanks

 

Oil change?

Check to see if the person did a coolant bypass mod. (Gives a surging idle)

May need to adjust the idle screw on the TB to 700-750rpms or so.

If it has a lot of mile on it, you might need to clean the injectors. I had a bunch of carbon on mine when I placed a fuel rail on the other month.

 

vacuum hose?

 

Thanks for the suggestions. The oil was recently changed. I should also mention that this car is bone stock, however it does have 200k on it.

Thanks

 

Have you tried cleaing the throttle body? I had rough idling on my 95 prelude due to unclean throttle body and after cleaning it with CRC intake throttle cleaner (don't get the carborator cleaner) it was much better.