Mohit1

renault duster misfire when cold

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Hello All,

I am a new user here, just registered was referred by Rahimdad.

So here is the issue that I am facing with my car,  every morning when i start the car it misfires until the temperature becomes adequate.

I changed spark plugs twice, spark plug cables are ok as tested by mechanic.

there was no engine light on dashboard until today morning when trying to check vacuum for air  suction, while checking if there is air suction happening properly check engine light came on.

 

No computer diagnostic were done so far as check engine light or any other light never showed on dashboard.

Car runs perfect once temperature is fine .

Also got cylinders tested with power loss which also is not there.

I had doubts with o2 sensor or mapping sensor but mechanic just wants to try different stuff that I am not convince on.

removed the mapping sensor and car switched off immediately, ....

Please advise if anyone has any idea about the issue. 

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2 spark plug changes and randomly suggesting changing parts with no diagnostic checks? Time to find a new mechanic. 

Just because the check engine light isn’t illuminated doesn’t mean there are no codes stored so start with a basic code scan to see what comes up. Run some live data, check MAF and MAP values and long and short term fuel trims and you’ll have an idea of what’s going on. Basic stuff really that any decent mechanic will do before changing anything. 

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Thanks Barry, the thing is that i went to a couple of mechanics in al qusais and Sharjah all want me to leave the car with them over night to see the issue when car is cold.

I dont get convinced because why do they need car to be cold for diagnosis when computer checks generally figures out regardless of temperature.

i want diagnosis in front of me, else they will try something, obviously before the car is delivered it will kept on and nothing is wrong when car is hot ..... so next day i may end up having same issue ...

 

I went to another guy who has a computer he doesnt mind running diagnostics but insisted that i should leave the car overnight and he will run test in morning.

 

I am doubtful of o2 or mapping sensor voltages, lastly just a dirty throttle body

 

 

funny thing by the time i reached home CEL was gone

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Sometimes, and depending on the fault, some TDC's will reset automatically when the ECU senses that the fault is no longer present, such as the fault you created when you disconnected vacuum lines.

As @Barry said, find a decent mechanic that can do a proper scan of the car's fault memory, because sometimes, some faults can be stored as "pending" codes that need to be registered by the ECU for a set number of times before a CEL light will come on.

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