Idle surging and dropping but RPM meter remains stable Topic is solved

[jpeter]

Help please. Bought 2003 Volvo XC90 2.5T yesterday. It has loping and surging of the engine at idle (when running it is absolutely fine) with CEL; hooked up a scan tool which showed multiple codes (please find attached pics). There are no visible vacuum leaks but there is kinna hissing/turbo sound when flooring the accelerator. I am not sure where to start looking and there aren’t many good mechanics in Qatar other than the dealer.

My issues are very similar to this video I found in youtube (but I have CEL)

[RickHaleParker]

Did you clear the codes to determine what DTCs are current and which ones are artifacts?

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P0017 = ECM-644A Camshaft position, exhaust Signal too low

Diagnostic trouble code (DTC) information

D2102380 Condition
The control module checks that the camshaft is in the correct position in relation to the position of the crankshaft. If the position of the camshaft is incorrect, the control module will adjust the adaptation for the camshaft. Diagnostic trouble code (DTC) ECM-643A or ECM-644A is stored if the adaptation becomes too great.

Substitute value

• None.

Possible source

• Signal too high
  Poor oil quality
  Incorrectly adjusted camshafts
  The timing gear belt has jumped off the cogs
  Defective reset valve
  Mechanical fault in the variable valve timing (VVT) unit.
  
  Signal too low
  Poor oil quality
  Incorrectly adjusted camshafts
  The timing gear belt has jumped off the cogs.

Fault symptoms

• Malfunction indicator lamp (MIL) lit.

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P0031= ECM-2810 Front heated oxygen sensor (HO2S), preheating Signal too low.

284: ECM-2810 Front heated oxygen sensor (HO2S), bank 1 heating. Faulty signal. Intermittent fault

Diagnostic trouble code (DTC) information

D2500821 Condition
The control module controls preheating by pulsing the current to the PTC-element. Pulse lengths are dependent on heated oxygen sensor (H02S) temperature. Diagnostic trouble code (DTC) ECM-2810 is stored if the control module registers that the signal is constantly 2.5 V, higher than 3.5 V at current pulse or lower than 2.3 V at no pulse.
Diagnostic trouble code (DTC) ECM-2810 is stored if the control module registers that heated oxygen sensor pre-heating does not function within 17 seconds of dew (condensation) point in the exhaust system being reached.

Substitute value

• fuel trim shut off.

Possible source

• Signal too high:
  short-circuit to supply voltage in the signal cable
  defective heated oxygen sensor (HO2S).
  
  Signal too low:
  short-circuit to ground in the signal cable
  defective heated oxygen sensor (HO2S).
  
  Signal missing:
  contact resistance and oxidation
  open-circuit in power supply from system relay.
  Faulty signal:
  defective heated oxygen sensor (HO2S).

Fault symptoms

• MIL-lamp lights.

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P0141 = ECM-2A2A Rear heated oxygen sensor (HO2S), preheating Faulty signal

284: ECM-2A2A Rear heated oxygen sensor (HO2S) preheating. Faulty signal

Diagnostic trouble code (DTC) information

D2500823 Condition
Diagnostic trouble code (DTC) ECM-2A2A (bank 1) is stored if the control module registers that the resistance of the rear heated oxygen sensor (HO2S) in the pre-heating circuit is too high for a certain amount of time.

Substitute value

• None.

Possible source

• Faulty signal:
  Contact resistance and oxidation
  Defective heated oxygen sensor (HO2S).

Fault symptoms

• The malfunction indicator lamp (MIL) lights.

[jpeter]

Thanks for the elaboration. I have had the trouble code deleted today, will take it to the shop again for a rescan.

[jpeter]

Cleaning the throttle body and MAF solved the issue.