Fig. 1 Intake manifold pressure sensor/MAP sensor (MAP = Manifold Air Pressure)

Intake manifold pressure error at idle

Troubleshooting in vehicles with MAP sensors

Pierburg | Motorservice
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Information on diagnostics

Fluctuating idle speed? Engine jerking on acceleration? Diagnostic trouble code P0105, P0106, P0107, P0108 or P0109 in the fault code memory? This suggests a problem with the intake manifold pressure, but the cause is not always to be found in the MAP sensor (intake manifold pressure sensor). Click here for a handy checklist to use when troubleshooting engine issues.

Error messages relating to the intake manifold pressure often appear in petrol engines that have intake manifold pressure measurement via a MAP sensor (MAP = Manifold Air Pressure).
Deviation from the set-point values does not, however, lead to the diagnostic trouble code being stored in all operating states.
Determining the source
A scan tool can be used to compare the actual values with the set point values. If the intake manifold pressure measured by the system deviates from the set-point value, the actual value must be checked using a separate vacuum manometer.
  • If the measured intake manifold pressure is within the set-point values, the MAP sensor and the electrical lines must be checked.
  • If the measured intake manifold pressure is outside of the set-point values, the reason for the loss of pressure in the engine must be established (see test instruction that follows).
Fig. 1 Intake manifold pressure sensor/MAP sensor (MAP = Manifold Air Pressure)
Fig. 2 Intake manifold pressure sensors (red) in a VW Golf IV
Potential complaints
  • Fluctuating idle speed
  • Loss of power
  • Jerking on acceleration
  • Malfunction indicator lamp lights up
  • Diagnostic trouble code P0105 – P0109

Possible fault sources in the engine periphery

  • Leaking intake manifolds downstream of the throttle valve (e.g. due to defective intake manifold gaskets, hoses, etc.)
  • Defective engine exhaust valves/hoses
  • Leaking brake boosters
  • Leakages in the vacuum system (e.g. vacuum-operated actuators, brake boosters, lines, etc.)
  • Defective EGR valves (permanently open)
  • Defective idling actuators
  • Idling status of the engine is not recognised by the control unit (defective throttle potentiometer, throttle switch)
  • Defective or dirty throttle valves
  • Incorrect or faulty air fi lter inserts
  • Carbon deposits or other blockages in the intake manifold
If the problem is not found in the engine periphery, it must be assumed that there is a mechanical problem with the engine.

Possible fault sources in the engine mechanics

  • Piston ring wear or piston damage (piston seizure, fusion and and similar damage) – a further sign of this is high blow-by gas emission during idling with the oil fi ller cap open.
  • Leaking intake and exhaust valves
  • Insuffi cient valve clearance
  • Worn valve seat inserts (especially in engines with gas conversion)
  • Incorrect function of the hydraulic valve clearance compensating elements (hydraulic tappet)
  • Incorrectly set valve timing or skipped toothed belt
  • Leaking cylinder head gaskets
  • Incorrect or worn camshafts
Inspections to be carried out
  • Valve clearance
  • Valve timing check
  • Compression test
  • Cylinder compression test

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