Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSACURA19983.5RL SPECIAL EDITIONREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODESDIAGNOSTIC TESTSDTC P0505: IDLE CONTROL SYSTEM MALFUNCTION
1998 Acura 3.5RL Special Edition
DTC P0505: Idle Control System Malfunction
1998 Acura 3.5RL Special EditionSECTION DTC P0505: Idle Control System Malfunction
NOTE:
Trouble shoot DTC P1508, if set at same time, before proceeding.
- If DTC P0505 is set, check the following:
- IAC valve mechanical malfunction.
- Fast idle thermovalve malfunction.
- Clogged throttle body port or improper adjustment.
- Intake manifold and/or manifold gasket leak.
- Intake air hose loose and/or leaking.
- Vacuum hose leaks.
- Incorrect ECT sensor signal.
Repair as necessary. If no problems are found, go to next step.
- Start engine and run at 3000 RPM with no load and transmission in Park or Neutral, until radiator fan comes on. Allow engine to idle, check idle speed data under no-load conditions (all accessories off), using scan tool. See IDLE SPEED SPECIFICATIONS
. If idle speed is within specification, problem is intermittent. System is okay at this time. If idle speed is less than minimum specification, go to next step. If idle speed is more than maximum specification, go to step 4).IDLE SPEED SPECIFICATIONS
Application Specification 3.5RL 600-700 RPM - Disconnect IAC valve 2-pin connector. If engine speed drops or engine stalls, adjust base idle speed. If base idle speed cannot be adjusted, clean ports in throttle body. If engine speed does not drop, replace IAC valve.
- Turn ignition off. Remove cover from fast idle thermovalve. See Fig 1 . Start engine and allow to idle. Feel for airflow at valve seat. If airflow does not exist in valve seat area, go to next step. If airflow exists in valve seat area, check coolant level and for air in cooling system. If okay, replace fast idle thermovalve.
- Check for vacuum leaks and ensure throttle valve is fully closed. Adjust idle speed. If idle speed cannot be adjusted, replace IAC.NOTE: After removing and replacing fast idle thermovalve cover, perform PCM reset procedure. See procedures under PCM RESET PROCEDURE/CLEARING CODES under SELF-DIAGNOSTIC SYSTEM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.