Hyundai Repair: 2000 Hyundia Elantra, intake manifold gasket, oxygen sensors

Question
QUESTION: Hi...I had check engine light come on trouble code was P1124 mechanic changed both o2 sensors and throttle postion sensor engine light still on. Car does have idle surging if stopped at about 1500-1800 rpms and sometimes has rough idling in drive and park. any suggestions would greatly be appreciated :)

ANSWER: P1124 indicates a lean condition at idle.  The high rpm along with this code suggest that the problem is air leaking into the engine without having to pass through the throttle body.  Check the PCV hose and intake manifold gasket for leaks.

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QUESTION: I forgot to say that feul consumption has been an issue too...thanks again


Answer
Excessive fuel consumption is consistent with an air leak such as those I've mentioned.  The lean readings from the oxygen sensors (due to the air leak) will cause the engine control module (ECM) to try to continue enriching the fuel mixture to try to return the oxygen sensor readings to their normal state.