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Nelson Garcia
Nelson Garcia, Mercedes Technician
Category: Mercedes
Satisfied Customers: 1094
Experience:  6 Years Mercedes Benz Dealer Technician, 5 Years Master Certified
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W203 C180 (non kompressor) Hi, I have a problem with idle

Customer Question

W203 C180 (non kompressor)
Hi, I have a problem with idle fluctuating for the 1st minute or so after a dead cold start up. Ive replaced MAF, coolant temp sensor, inlet manifold gaskets, checked compression, plugs, ect
I suspect the throttle body but after its minute of fluctuating, it drives great.
Submitted: 7 years ago.
Category: Mercedes
Expert:  Nelson Garcia replied 7 years ago.
Take a look at the variable cam adjustment magnet that is located next to the coolant temp sensor. It is mounted on the head in the front of the cam. Check the electrical connecto to see if there is oil contamination in it.
Customer: replied 7 years ago.

Hey Nelson

Sorry, I should have mentioned it looks like the cam magnet has been done before and it has the superseeded short harness fitted to that magnet. The rest of the harness looks free from oil, right down to the plugs for the oxy sensors..

This problem is so consistant. At a stone cold startup, it starts no trouble, then if you alter the idle ie: putting in to gear or tap the throttle, the throttle body has a tough time stabilising the rpm unitl the coolant temp reads around 30deg C, then everything behaves as it should.

Expert:  Nelson Garcia replied 7 years ago.
When the retrofit was performed it is normally done because oil gets into the harness and gets to the computer. Did this happen if so make sure there is no oil in the computer. Random problems can occur from this. Aso check for engine codes even if there is no light on. Sometimes it will trigger a silent fault that can help.

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