Sounds like it's revving too high

[jt1-75]

Hello all,

My friend has a 2005 Corolla with 195,000 km's on it. It's well maintained and in great condition. But lately, when in 5th gear on the highway at cruising speed, 80 - 100 km/hr, the tachometer says its at 2000 rpm's, but it sounds like it's at 6000 rpm's. It's not a performance car. It's a basic 4 cylinder. She doesn't know much about cars, but takes good care of it as far as basic maintenance. I tried to tell her she doesn't need premium fuel as it's not a high compression engine, but she believes it's better, and I don't think that would cause this anyways.  Any ideas on what it might be?

[Roy231]

Sounds like clutch slip but if the Rev Counter stays low ?

Check underside of car could be a loose heat shield around exhaust.

 

 

[Bper]

Hi Jeremy,there are a couple of possible explanations for the significant discrepancy between the engine noise and the tachometer reading in your friends Corolla.MAF Sensor Fault,this is a strong possibility. A faulty MAF sensor, Mass Air Flow sensor can under report airflow entering the engine. This leads to a lean air fuel mixture too much fuel, not enough air. To compensate, the engine might work harder (higher RPMs) even if the tachometer doesn't reflect this increase fully. This higher RPM can explain the increase engine noise.Tachometer Malfunction,while less likely than a MAF sensor issue, a faulty tachometer could be displaying an incorrect, lower RPM reading. This would explain why the engine sounds loud despite the low reading on the tachometer.

Less Likely, But Possible,Vacuum Leak A small vacuum leak could also contribute to a lean mixture and slightly higher RPMs, although this is less probable due to the absence of other symptoms typically associated with leaks rough idle, hesitation during acceleration.If you are unable to check these yourself it would be better to book it into a garage or a mechanic.

Check the MAF sensor operation and readings.Assess other sensor data and engine performance.Test or replace the MAF sensor if necessary.Verify the tachometer accuracy using diagnostic tools.

Inspect the intake system for vacuum leaks.

By performing a inspection, the mechanic can identify the exact cause of this issue and ensure your friends Corolla runs smoothly and efficiently.Hope this helps.🙂

[jt1-75]

That is great info and makes sense. Thank you very much.