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Hello, I originally posted this message in the ML section of the forum but I think it is a more appropriate post here. I am hoping that some experts out there might be able to help me diagnose a problem I have been experiencing. My '99 ML320 has 76K miles on it. All regular maintenance has been performed by Mercedes up to and including 60K mile service. The spark plugs were part of the last service. They would now have 15K miles on them. They were replaced with Bosch plugs just like from the factory.
I noticed yesterday the engine was missing like a cylinder wasn't firing from the moment I started the car. It doesn't seem to make any difference what temp the car is running, it is consistenly missing even after it has reached running temp. The check engine light has never come on since this problem has occurred. I pulled all the ignition wires and tested them with a multimeter. All were between 2100 and 2300 except one which was only 8.9 so in other words basically a dead wire. Rather than messing with replacing only one wire I replaced the entire set with new wires. I am still having the same problem even with new wires. Took it over to a buddies house who is a mechanic (but not a Mercedes mechanic) who said he thought that a fuel injector may be clogged. I know Mercedes doesn't recommend using fuel injector cleaner but I dumped a bottle of Valvoline cleaner into the tank anyways to see if it helps out.
I drove through the McDonalds drive through today and since I was right up against the wall I could more easily hear the engine sound reflect back to the car. I could hear a fluttering sound come from the engine which definately is a wierd sound and overall it just has no power. Under heavy acceleration on the highway it almost sounds like a Chevy small block V-8 with a manifold leak or something. That's about the best description I can come up with as to how it sounds. I can smell gas fumes after I've parked it in the garage which isn't normal.

Any ideas? Thanks in advance!
John
 

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noise

you most likely have a cracked weld on one of the catalytic converters. this should be covered by the 8 year/80,000 mile emissions warranty. let me know if this works out for you
 

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Thanks for the post. Ended up taking the car into MB of Cincinnati. Sure enough...one Cat was bad. It was indeed covered under warranty. I tried to get them to warranty the other one too but no luck there. The other cat hasn't failed so it couldn't be warranted. I only have 2500 miles left under my warranty so I figured it was worth a shot. I wonder how long it will be until the other one fails.......

Thanks!
 

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Your cats have a federally mandated 8 yr/80000 mile warranty on them. No worries. Because of this, almost every single one warrantied by a dealer undergoes rigorous inspection by the powers that be at the MB warranty center. If it is not deemed bad by them, the dealer is charged for it. That's wwhy they won't do both at once for you.
 
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