P1518 on Mercury
Intake Manifold Runner Control Stuck Open
P1518 on Mercury vehicles indicates intake manifold runner control stuck open. Au7o has documented this code across 1 Mercury model — most commonly on Cougar. This manufacturer-specific code (common on Ford, Lincoln, and Mercury) indicates the intake manifold runner control (IMRC) is stuck in the open position. The IMRC uses butterfly plates in the intake to change air-passage length and improve airflow across the rpm range; the computer commands them closed at lower rpm but here detects they remain open. When the system commands 'closed' but the monitor still reads 'open,' P1518 sets. The result is often weak low-end torque, rough idle, and reduced fuel economy. Typical repair costs on Mercury range from $120 to $600, depending on the specific model and root cause.
Common Causes of P1518
- •Stuck or broken IMRC actuator
- •Seized or carbon-fouled runner butterfly plates
- •Broken or disconnected IMRC linkage
- •Open or shorted actuator wiring
- •Corroded or loose IMRC connector
- •Weak or broken return spring
- •Faulty PCM/ECM (rare)
P1518 on Mercury by Model
Mercury Cougar(1 issue)
- Intake Manifold Runner Control (IMRC) Failure - 2.5L V61999-2002
The 2.5L Duratec V6's IMRC system uses an electric actuator with plastic gears and plastic linkage bushings to open the secondary intake runners at higher rpm. The plastic linkage bushings break and the actuator's gears jam or strip — a failure common to all Fords with this IMRC design — leaving the runners stuck closed (P1519) or stuck open (P1518). With the runners stuck closed the engine loses most of its power above roughly 3,000 rpm and the check engine light prevents passing emissions testing.
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View P1518 across all makes →Frequently Asked Questions
What does P1518 mean on Mercury?▼
P1518 stands for "Intake Manifold Runner Control Stuck Open." This manufacturer-specific code (common on Ford, Lincoln, and Mercury) indicates the intake manifold runner control (IMRC) is stuck in the open position. The IMRC uses butterfly plates in the intake to change air-passage length and improve airflow across the rpm range; the computer commands them closed at lower rpm but here detects they remain open. When the system commands 'closed' but the monitor still reads 'open,' P1518 sets. The result is often weak low-end torque, rough idle, and reduced fuel economy. On Mercury specifically, this code is documented across 1 model.
What causes P1518 on Mercury vehicles?▼
Common causes on Mercury: Stuck or broken IMRC actuator, Seized or carbon-fouled runner butterfly plates, Broken or disconnected IMRC linkage, Open or shorted actuator wiring, Corroded or loose IMRC connector. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P1518 on a Mercury?▼
Repair costs on Mercury range from $120 to $600, depending on the specific model and root cause.
Which Mercury models have P1518 documented?▼
Au7o has documented P1518 on 1 Mercury model: Cougar.