For your heat, I would check the monovalve. Also, when is the last time that your coolant was flushed and refilled?
For the hard starts, try some Lubro Moly Jectron fuel injection cleaner and the Ventil Sauber valve cleaner. Here's a link:
https://www.autohausaz.com/membersonly/lookup_parts.cfm?SubcategoryID=2222&CFID=548340&CFTOKEN=67577146
I had a hard starting problem myself and my mechanic bought me some of this to use. Now I just tried it yesterday and my MB has been starting much easier and cleaner. Matter of fact, this morning I gave the 420 a good blow out on the highway.
For the sputtering. When is the last time you checked your spark plugs or had a tune up? Also, check your plug wires and connectors. Hopefully this helps you. Have a good day!
For the hard starts, try some Lubro Moly Jectron fuel injection cleaner and the Ventil Sauber valve cleaner. Here's a link:
https://www.autohausaz.com/membersonly/lookup_parts.cfm?SubcategoryID=2222&CFID=548340&CFTOKEN=67577146
I had a hard starting problem myself and my mechanic bought me some of this to use. Now I just tried it yesterday and my MB has been starting much easier and cleaner. Matter of fact, this morning I gave the 420 a good blow out on the highway.
For the sputtering. When is the last time you checked your spark plugs or had a tune up? Also, check your plug wires and connectors. Hopefully this helps you. Have a good day!