Code
P1190
BUICK
P — Powertrain
Engine Vacuum Leak
AI status
Completed
Completed
100%
Causes
- Cracked/broken vacuum hoses or fittings
- Damaged intake manifold gasket or seal
- Loose or leaking throttle body-to-intake or intake plenum bolts
- Faulty or stuck PCV/vent valve
- Leaking brake booster check valve or booster hose
- Improperly sealed intake components after service (vacuum lines disconnected)
Symptoms
- Rough or high idle
- Hesitation, stumble, or poor throttle response under light load
- Illuminated Check Engine Light with lean-related codes or fuel trim issues
- Increased fuel consumption
- Possible misfire(s) under some conditions
What to check
- Read freeze frame and stored data from the PCM; note conditions (engine temp, RPM, load) when code set
- Scan live data: short-term and long-term fuel trims, MAP (manifold absolute pressure) or MAF readings, O2 sensor switching
- Visually inspect all vacuum hoses, fittings, and clamps for cracks, disconnections or abrasion
- Inspect PCV valve and hoses for correct operation and secure connections
- Check intake manifold, throttle body and plenum for loose bolts, damaged gaskets, or signs of leakage
- Listen for hissing noises around intake and vacuum lines at idle; use a stethoscope or backprobe area safely
Signal parameters
- Manifold vacuum at idle (typical gasoline engine): ~17–22 inHg (57–74 kPa) — large, sustained deviations may indicate leak
- MAP sensor: lower than expected manifold pressure (lean conditions) or erratic readings
- MAF sensor: unexpected high airflow for given RPM/load (unmetered air)
- Short-term fuel trim (STFT): rapid positive swings can show transient lean condition
- Long-term fuel trim (LTFT): sustained positive LTFT (+10% to +25% or higher) suggests unmetered air/lean condition
- O2 sensors: slower switching or O2 voltage indicating lean (low voltage)
Diagnostic algorithm
- Verify code and capture freeze frame and live data with a scan tool under the same conditions the code set
- Check for related DTCs (lean, MAF, MAP, misfire) that can help narrow cause
- Visually inspect vacuum hoses, fittings, intake gaskets and throttle body for obvious leaks or loose connections
- With engine idling, carefully listen for hissing and spray a small amount of safe propane or carb cleaner around intake gaskets and vacuum lines while monitoring RPM and fuel trims for change (use appropriate safety precautions)
- If no obvious leak is found, perform an intake/vacuum smoke test and repair any leaks found
- Inspect/replace PCV valve and hoses if they appear degraded or stuck; verify correct operation
- Verify MAP/MAF sensor readings against manufacturer data; clean or replace sensor if out of range
- After repair, clear codes, road test, and monitor STFT/LTFT and O2 response to confirm code does not return
- If code returns despite no vacuum leaks, perform further diagnostics on EVAP purge circuit, fuel pressure, and intake runner control (as applicable)
Likely causes
- Aged or disconnected vacuum hose(s) at nipple fittings
- Intake manifold gasket leak (common at high mileage or after servicing)
- Failed PCV valve or hose causing unmetered air
- Loose throttle body or intake plenum bolts/seal
Fault status
Status
Engine vacuum leak detected (unmetered air intake) — possible lean condition.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email