I bought my 2007 CLK 550 in March as a CPO vehicle with 27k miles, and I haven't done anything to it. It includes the AMG package, but otherwise is completely standard. It's my first Benz, and I'm totally in lust with it. Last week I drove from the SF Bay Area to Palm Springs (500 miles), and it was simply delightful to drive. I didn't go too far over the speed limit on I5 (can't afford the speeding tix), and it averaged exactly 25 mpg door to door. It worked fine that evening, and fine the next morning. I parked it in what meagre shade I could find, but the temperature in the shade was about 112 degrees. When I came back to the car and started it, at first I thought it was in limp home mode. It was misfiring badly, and would hardly move. Over the next couple of minutes as it warmed up it improved, but was still badly wrong, and the "check engine" light stayed on. I took it to the Palm Springs dealer who were great (thanks guys!!), and they had it fixed within the day. They said an air filter o-ring was leaking, and replaced the o-ring and filter. Since then the car has been even better- smoother, quieter, and on the way home averaged 26.5 mpg. I have two thoughts: why did an o-ring fail in this way (that is, it worked fine for months and on a 500 mile drive, but failed when parked in 112 degree shade), and how would anyone know that it wasn't right in the first place? I was totally happy with the car before this happened, but it seems that the o-ring must have been leaking for months letting in un-regulated air. Presumably it was running too lean all the time?

No big issue here, but it worries me that I own a car so complicated that I don't even know when it isn't running right. Thoughts? Thanks!

 

If the air was 'unregulated' it would have to be leaking in after the MAF, anything before that (between it and the airfilters would have no effect other than being unfiltered air. It sounds to me like it may have been something regarding a vacuum leak, I've seen lots of those cause issues exactly as you describe.

Regardless, glad to hear that you're back up and running. Lets see some pics!

 

Sorry for the delay in responding, and thanks for your input. I did a bit of Googling on the MAF issues, and you're right - they can cause all sorts of weird problems. The codes the dealer reported on my car were: "air filter seal ring - leaking (09103-04 7)" and "Performed short test, found DTCs 0746, 2092, 0750, 2096." As noted earlier, the dealer said it replaced one air filter, an air filter seal ring,and one gasket. All work was under warranty, so I don't know if the dealer exaggerates things. I don't know if these codes mean anything to anyone, but certainly the car has gone from great to even better.

Here's a couple of pics - it's a totally stock '07 550 Cab with AMG package. But the colour is what sold me.

Thanks!

 

what exactly is the "air filter o-ring" ?

Edit: Your colour is sold me too .

Andy

 

Dunno. "O-ring" was the verbal report from the dealer. The actual service report from the dealer says (in addition to the earlier quotes) "090000 Air Filter Seal Ring, Repl. 296, W08". The whole thing seems weird to me, but because these cars are so far out of my experience is why I thought I'd see what the forum thought.

The colour is called "Black Opal" but it's like a really deep midnight blue metallic, but with tinges of green under certain light values.

BTW - anyone know of any Merc knowledgeable independent mechanics in the SF Bay Area? I'm losing confidence in my local dealer.

Thanks!!

 

hmm..interesting. Did you actually see the parts that they replaced ? I mean I have taking out our airbox apart but just not sure what that is....

Andy

 

Nope. Didn't see any parts. I was on vacation at the time, 500 miles from home, and just grateful to have my car back (the car is a great chick magnet, but not so impressive when it breaks down and has to spend time in the shop on a road trip!). And since it was all warranty work, I didn't think about asking to see parts.

But the car really does run smoother, quieter, and with significantly better MPG since the work. So they did do something to it.

Thanks!

 

I kinda agreed on the "chick magnet car" lolz.

Andy

 

what it sounds like that happened is that your air filter housing was not properly put on, maybe the gasket/oring around where it seals the filtered air to the MAF was pinched or loose causing unfiltered air to enter into the engine. eventually enough dirty can build up on the MAF itself causing it to run in limp mode and misfires. the dealer must had replaced the gasket and deemed the MAF to be fine (maybe some cleaning). which local dealer do you bring your vehicle too?

 

it makes sense now.

Andy

 

I think you maybe hit the nail on the head with the leaky airfilter housing, and perhaps a dirty MAF sensor. Thanks. My local dealer is RAB Motors in San Rafael. This is my first Mercedes, so I've no experience of them prior to this.

 

I've seen MB techs refit the air filter housing over the 4 'bulbs' on the engine, and then bang the plastic cover down with their fist.

I asked them why, and was told that if the cover is not absolutely snug on the air inlet seal, it will throw fault codes as the mixture is not quite right.

Maybe this is all that was wrong with your car....