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Discussion Starter #1
Just had our Beetle back from the dealer. The engine management light and esp light was on. Turned out to be a dodgy exhaust sensor which was changed. The car seems to run more smoothly now. Am I imagining this or can replacing a sensor change the engine performance?Edited by: Scrubnut
 

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The 'exhaust sensor' will be a Lambda sensor, which measures the exhaust gasses and controls the air/fuel ratio accordingly to get the most efficient combustion from an engine.

If the sensor is faulty, it will result in an engine which runs too lean or too rich in fuel, which most definitely will have a detrimentally negative effort on the performance and running of an engine.



Edited by: shakotanVIP
 

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I thought that the sensor monitors the car and warns if there is a problem. If the sensor is faulty doesn't it mean its either warning of a problem that's not there or not warning of a problem that is? I have just had a sensor replaced on another car I own and within a few miles the warning light came on again. Doesn't that mean the sensor wasn't faulty?
 

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the sensor is part of a feedback loop, it measures O2 and tells the ECU to vary the air/fuel mix accordingly, if the varience is achieved, all well and good, if the max varience allowed still causes the sensor to ask for more, then the ecu/check engine light will illuminate and a fault code will be stored. you can check the fault codes with a simple OBD2 scanner or dongle & iOS program......the check engine light doesn't mean the sensor is faulty, it could be any number of things best get your dealer to check if you don't have a scanner or OBD dongle (see my other posts re OBD2 Diagnostics)
 

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Beevee said:
I thought that the sensor monitors the car and warns if there is a problem. If the sensor is faulty doesn't it mean its either warning of a problem that's not there or not warning of a problem that is? I have just had a sensor replaced on another car I own and within a few miles the warning light came on again. Doesn't that mean the sensor wasn't faulty?
The only thing a Lambda sensor monitors is O2 levels in combustion gasses, it is not a universal sensors that looks for all different issues, it serves one purpose only.

The ECU uses the readings from the Lambda sensor to alter the combustion ratio of air/fuel mix, so if the sensor is faulty, it will result in the ECU getting false information.

Was the sensor replaced on your other car a Lambda sensor, or another. Most modern cars have multiple sensors in the inlet tract and on the engine itself as well as the O2 sensor in the exhaust, and they will all throw up 'engine' warnings if faulty.
 

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Discussion Starter #6
Thanks for all the info!

I thought it was on a feedback loop which explains how the engine is running more sweetly now. Just wanted to check in case it just put a light on and didn't do anything else!
 
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