I have a sweet 1997 E320, but about two months ago the Check Engine light came on. I own a scanner, so I ran the code and it stated there was a missfire. A few days later the check engine light went off. Only to come on again within a few weeks? Then off again after a few days. I took it to a Benz certified repair shop today, and they ran the codes and said there was a miss fire. I said ok, why? He said he didn't know, but he cleared the codes and the light is off. Im sure it will come on in a few days or a week. Any ideas? I have 99K on the car, I think the plugs are due a change. Any other ideas?
Missfire codes can come from a few sources. Since you're aware the plugs are due, I'd start there. If it comes back you can look at the others. While you're in there, it probably wouldn't hurt to clean the MAF.
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Take care and enjoy the ride,
Greg
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Vehicle: E320, SLK320, MKV Jetta TDI, Mini Cooper S
Location: Arizona
Posts: 1,678
It could be as simple as changing the plugs. You can do that yourself with ease on the inline 6. Make sure you put the factory recommended Bosch ones in. You want to get rid of misfires and not cause other ones. Then look at your plug wires to see how good they are. If the are still the ones that came with the car, then think about replacing them with the factory recommended ones as well. Don't use cheap substitute parts or install Platinum plugs on the MB inline 6. The engine codes should be able to tell you what cylinder is missfiring unless it is just random. You might want to get your fuel system cleaned as well.
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New update, the shop stated that it is always cylinder 6 and 1 that are miss firing. They share a common coil ontop of cylinder 6 spark plug. They recomment a complete service of the vehicle @ $960. ???? I checked on line, the spark plugs are like $4 a piece (Do they come with the gap preset if they are bosch?) The coils are like $55 a piece. Not sure on new wires. Is this a "Do it Yourself Job"? How hard and do I need any special tools, other than a spark plug wrench?
Vehicle: E320, SLK320, MKV Jetta TDI, Mini Cooper S
Location: Arizona
Posts: 1,678
IT is all a DIY job. I recommend checking the gap on the new plugs before installing them. It is good that they told you that the misfire was common with the one coil. That is easy to replace. You have to pull the coil to get to the spark plug anyway. There are 3 coils for the 6 spark plugs with each operating 2 plugs. A boot come streight down from the coil to connect with one plug and then there is a wire to go to the second plug. Just detach the coil for plugs 6 and 1 while you are replacing the plugs and install the new coil when you put it back together. To get to the plugs and coils you just have to remove the crossover tube for the air intake and then pull the cover that runs down the center of the engine. You just need some metric allen head wrenches if I remember correctly. No special tools needed.
Thanks E-Klasse, I think I will do it myself and same the $960 they quoted me for the major service. I can pick up the airfilters cheap and put them in also and I think I have covered everything they would have done with the plug changes and new coil.
1997 E320 Check Engine Light - Misfire 
Linear Mode
