E-Series Spark Plugs
Thread Starter
Newbie
Joined: Aug 2003
Posts: 21
Likes: 0
From: N. Alabama
E-Series Spark Plugs
My new (to me) 1988 300CE was idling a bit rough, so I changed out the plugs and ignition wires. The car has 70K miles on it, and the wires were obviously original. The plugs I pulled out were Champions?. Installed new Beru wires, but could not readliy find the recommended Bosch copper core H8DC plugs locally, so I put in a set of NGK substitutes. It ran decently for a 100 miles or so, then the rough idle came back. Pulled the plugs again, all were black and sooty, especially #s 1 and 3, which were oily and fouled looking. I picked up a set of slightly hotter Bosch H9 DC 0 copper cores, and put them this morning. The H9 DC 0 seems to be the plug of choice on this forum. My question is, should I be worried about the condition of plugs 1 & 3 at this point, or just run them awhile and see what happens? Is this fairly common with these cars? Thanks for the great advice as always. Don
Member
Joined: Mar 2004
Posts: 193
Likes: 0
From: Miami, FL
ex 300E driver
The oily plugs is the tell tale signs of neeeding new valve stem seals, or the more costly route, a valve job. Just run the H9DCO for a while and then pull them. If they have the oily coating, then you know what is needed. Valve stem seal replacement is about $150-$250, and the valve job will run you $1000.
