Diagnostic guidance. Suggested checks and possible repairs are separate from the owner's reported results.
Have the installed fuel and idle-control system identified and diagnose the surging using its service information before changing adjustments or applying cleaners.
Source: This question and its visible discussion, including any clearly labeled editorial corrections. Owner reports are distinguished from other participants' experiences. Follow-up guidance is not a confirmed diagnosis.
Clean the throttle bore with carburetor cleaner, then turn the air bleed screw inward to lower the idle. On these Hondas, vibration can loosen that screw.
The owner of a 1986 Honda Prelude 5-speed 2.0 reports that the engine will not stop surging despite a full tune-up, a mechanic's machine diagnosis, and a vacuum hose check. The expert recommends cleaning the throttle bore with carburetor cleaner and turning the air bleed screw inward to lower the idle.
HELP! Prelude Won't quit serging
A 1986 Prelude 2.0 manual continued surging after a tune-up, a workshop visit and vacuum-hose checks. A reply suggested throttle cleaning and changing an idle adjustment.
Reported outcome: No successful repair was reported.
The discussion did not establish an incorrect idle setting or a dirty throttle bore. The suggested screw adjustment was not verified for the actual system.
