Intake Manifold Vacuum: Inspection
WARNING: This page is about a different car, the 2012 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.
- Warm up the engine.
- Remove the collector cover.
- Remove the intercooler. < Ref. to REMOVAL , Intercooler. >
- Disconnect the brake booster vacuum hose from the intake manifold, and attach the vacuum gauge.
- Install the intercooler. < Ref. to INSTALLATION , Intercooler. >
- Keep the engine at idle speed and read the vacuum gauge indication.NOTE: Condition of engine inside can be diagnosed by observing the behavior of the vacuum gauge needle as described in table below.
Intake manifold vacuum (at idling, A/C OFF):
Standard
-68.0 kPa (-510 mmHg, -20.08 inHg) or more
- After inspection, install the related parts in the reverse order of removal.
ENGINE CONDITION REFERENCE CHART
| Diagnosis of engine condition by inspection of intake manifold vacuum | |
|---|---|
| Vacuum gauge needle behavior | Possible engine condition |
| 1. Needle is steady but lower than standard value. This tendency becomes more evident as engine temperature rises. | Leakage around intake manifold gasket, or disconnected or damaged vacuum hose |
| 2. Needle intermittently drops to position lower than standard value. | Leakage around cylinder |
| 3. Needle drops suddenly and intermittently from standard value. | Sticky valve |
| 4. When engine speed is gradually increased, needle begins to vibrate rapidly at certain speed, and then vibration increases as engine speed increases. | Weak or broken valve springs |
| 5. Needle vibrates above and below standard value in narrow range. | Defective ignition system |