P1518: How to Diagnose & Fix — Intake Manifold Runner Control Stuck Open
2 vehicles · 2 makes · $100-$600 repair
How to diagnose and fix P1518: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Ford Contour · 1995–2000
The 2.5L Duratec V6 in the Contour (base V6 and SVT) uses intake manifold runner control (IMRC) butterflies that seize or break due to carbon buildup. This causes a noticeable loss of mid-range power and a check engine light.
Common Symptoms
- Loss of mid-range power
- Check engine light
- Rattling from intake manifold
- Poor throttle response between 3000-5000 RPM
- Hesitation on acceleration
- Reduced fuel economy
How to Fix
Remove and clean the IMRC butterflies and shafts. Replace the IMRC actuator solenoids if they have failed. Some owners remove the butterflies entirely for a slight performance gain, though this triggers a CEL.
Sources for this issue (3)
Mercury Cougar · 1999–2002
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.
Common Symptoms
- Check engine light with P1518 or P1519
- Noticeable loss of power above 3,000 rpm
- Sluggish top-end acceleration
- Failed emissions inspection
How to Fix
Replace the broken plastic linkage bushings (a few dollars in parts), clean and re-seat the actuator's plastic gears, or replace the IMRC actuator assembly outright. Verify the linkage on both banks moves freely after repair.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- F5RZ9F955AB IMRC linkage-retainer bushings, five packOEMFord F5RZ9F955AB replacement
Confirm the bushing dimensions and intact actuator/runner shafts before purchase.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (7)
- Intake Manifold Runner Control Stuck Closed | New Cougar Forumforum
- 2002 cougar imcr | Mercury Cougar Ownersforum
- SOLVED: How do I fix imrc on the 2002 mercury cougar p1519 - Fixyaforum
- Looking for intake manifold runner control please and thank you | New Cougar Forumforum
- code P1519 Inlet manifold runner control malfunction (Stuck Closed) | New Cougar Forumforum
- IMRC Stuck Open? P1518 | New Cougar Forumforum
- P1518 – Intake Manifold Runner Control Stuck Open (Ford, Lincoln, Mercury) – TroubleCodes.netarticle
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P1518 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1518 mean?
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.
What are the most common causes of P1518?
The most common causes of P1518 are: 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). The specific cause varies by vehicle.
How much does it cost to fix P1518?
Repair costs for P1518 range from $100 to $600, depending on the vehicle and root cause.
Which vehicles are affected by P1518?
Au7o has documented P1518 across 2 vehicle models from 2 manufacturers: Ford, Mercury.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.