P2004: Intake Manifold Runner Control Stuck Open — Bank 1
What to do
Expect a flat spot at low revs and possibly a rough idle, with full power still there higher up. Worth attending to rather than living with — on some engines a seized flap can eventually break loose and be drawn into the engine, and the cleaning job that prevents it is a fraction of the cost of what follows.
What this code means
The flaps that vary the intake manifold's geometry are stuck open on bank 1. They exist to change how air enters the cylinder — long path or short, swirling or straight — so the engine can have low-speed torque and high-speed breathing from one manifold.
Stuck open is the milder of the two failures. The engine keeps its top-end breathing and loses the low-speed effect, so the complaint is a flat spot low down and a general dullness in ordinary driving, with full power still available if it is revved. On a diesel it also costs combustion quality at idle, which shows as roughness and smoke.
Carbon is almost always the cause, particularly on direct-injection engines where no fuel washes over the intake tract to keep it clean. The flaps and their spindles accumulate a hard deposit until they seize, and that is a cleaning job rather than a component failure — though by the time it stores a code the deposit is usually substantial.
The reason not to leave it is set out under the component: on some engines a flap that eventually breaks free of its seized spindle can be drawn into a cylinder, which is a very expensive way to learn about a cheap fault.
Likely causes
Start here
- Carbon deposits on intake manifold flaps · moderate
- Seized manifold runner spindle · moderate
- Failed manifold runner actuator · moderate
Less common
- Disconnected or leaking vacuum hose · easy
- Broken manifold runner linkage · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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