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Juan Crespo
Juan Crespo, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 1516
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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Mbz 420 sel 1987 has rough idyling and staaling when cold

Customer Question

mbz 420 sel 1987 has rough idyling and staaling when cold
Submitted: 10 months ago.
Category: Mercedes
Expert:  Juan Crespo replied 10 months ago.

Hi there. Welcome to our site!

Most of the times, rough idle is caused by unmetered air entering the engine through bad gaskets or hoses or by a faulty auxiliary air valve. Get a can of carb or choke cleaner and carefully spray all the air hoses, around the intake manifold, auxiliary air valve, etc. If the idle gets better as you spray a specific area, that's where you'll find the problem.

Please let me know what you find and we can continue.

Best Regards.