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Occasional knocking sound when accelerating

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Hey guys,

I'm driving a 2014 w204 c180. Sometimes my car is having these 2 issues. Help appreciated. Thanks!

1. Especially when driving up slope, sometimes the car will produce this knocking sound (not sure if its from engine or transmission) for a while till gear shift. Only happen once a while. 

2. Sharp jerk when gear change from 2 to 1. Especially when you press on the gas hard on initial and release the pedal. The jerk is quite prominent. 

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What RON & brand of petrol are you using?

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@jtang. Esso Mobil ron 95.

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Knocking is your petrol RON. Use once 98 after every 5 tanks of 95.

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Thanks j888. Will try that. btw, RON 95 not suitable for W204?

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Generally speaking...RON 95 is sufficient for Merc cars...incl W204. I don't intend to speak ill of oil companies, but sometimes I have my suspicion that particular day in that particular station somehow the petrol could be tainted with lower RON.....particularly in our neighboring country.

So yes...j88 suggestion of using RON98 is a good idea, even better if you alternate the 95 & 98 or stay 98 all the way.

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Thanks jtang. I think I got what you meant. btw, do you have any idea what cause my other issue below?

2. Sharp jerk when gear change from 2 to 1. Especially when you press on the gas hard on initial and release the pedal. The jerk is quite prominent. 

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Are you referring to the down shift gear shock when it kicks down from 2 to 1? Or are you referring to the throttle lift off jerk at low gear?

Btw, has your car been tuned by some piggyback or remapped by a tuner?

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jtang, I'm referring to the downshift gear shock when it kicks down from 2 to 1. Yes, i went for trans flush and ECU remapped before. This issue happens event before the tuning was done.

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Try to reset the TCU (transmission control unit).  Should solve the problem. 

Watch this....

 

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Thanks jtang. I've pump RON98 over the weekend. No more knocking so far. Also reset the TCU as per video. Will monitor again. Many thanks bro.

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