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  #1  
Old 10-05-2016, 11:17 PM
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SLK320 Low Power

I have been looking for a manual transmission 2001 SLK320 for several years and bought one today. I don't pick it up until next week, but want to get input about the low power problem.

The car is absolutely pristine in every way. Everything works very well. Has 38,000 miles. No light on, and haven't been able to check for codes yet. The engine sounds great, runs smooth, but is noticeably low on power. My first thought was the variable length intake. My brother in law, a 25 year MB dealer diagnostic tech, said the mileage was so low that the intake runners are probably not the issue, but this was via text and I haven't talked to him in depth yet. I am anxious to draw codes, but I wonder if anyone has any experience with this problem.

I am excited about the car even with this problem. The car is outstanding in every other way and I bought it worth the money, so I am willing to work through this problem.

Thanks for the thoughts and comments from those familiar with the breed.

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Old 10-06-2016, 03:54 PM
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When you say 'low on power' are you referring to the acceleration or generally sluggish in general?


-Dmitry
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  #3  
Old 10-07-2016, 05:55 AM
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Air&Road, it's possible a restriction in the exhaust system is causing the power reduction ... say a failed catalytic converter or dead rodents.
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Old 10-07-2016, 07:41 AM
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Idles great. Sounds great. Starts great. Cruises great. Accelerates like it has a normally aspirated four cylinder. I expect a 320 to accelerate like a solid fuel missile.

Since I don't get the car home until next week I am probably jumping the gun with this thread since I hanve not yet so much as pulled codes and done a basic inspection.

Given that this car has variable length intake runners and cam timing manipulation, I thought maybe someone knew of a common trouble spot that could cause this. Especially since the engine is used in so many other models as well.
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  #5  
Old 10-07-2016, 11:50 AM
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Air&Road, an SLK320 has a V6 engine. If you have an SLK230 then it has an inline 4-cylinder engine. Which vehicle do you own?
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Old 10-07-2016, 12:19 PM
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Off the top of my head it sounds like the air mass sensor could be the problem. They common failure scenario is that they report less air than they should so the ECU trims the fuel resulting in loss of power on acceleration..........
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Old 10-08-2016, 06:28 AM
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Originally Posted by Ferdman View Post
Air&Road, an SLK320 has a V6 engine. If you have an SLK230 then it has an inline 4-cylinder engine. Which vehicle do you own?
As the thread title indicates, the thread pertains to an SLK320 that I bought Wednesday, but have not yet taken delivery. I also have an SLK230 that I wrecked about a year ago. I indeed jumped the gun with this thread, but I thought there might be a common Achilles heel with this engine that someone might be aware of. I am hoping that when I get my hands on it, a code will lead me directly to the problem.

The car is so pristine, that I think I will be good with whatever it takes to make it right.

My BIL the MB tech has been telling me since these cars came out in '99 that I should get a 320 instead of a 230 because it is so much faster. My 230 would mash you into the back of the seat, so I expected the 320 to feel like a rocket ship. Time will tell.

BTW, back when this car was new I was with my BIL while he was test driving my car. We entered a downhill entrance ramp that was a common route for his test drives. He said "an SLK320 will do 120 by the end of this ramp." I asked "how do you know?"

Also BTW, if my generic scanner doesn't retrieve a code that leads me to the problem, I will take it to my BIL and see if their are enhanced codes that will help. He will home in on it if I can't.
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Old 10-08-2016, 07:03 AM
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Air&Road, if the mass air flow sensor is bad the Check Engine light should be lit. I own a 1998 E320 with the V6 engine and it is very quick. As you mention an SLK320 should be as quick, if not quicker.

Surprised you didn't have your brother-in-law perform a PPI (pre-purchase inspection) and diagnose the problem before buying the car. That could have been used to negotiate a lower purchase price.
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Old 10-08-2016, 08:48 AM
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Hi Larry. Congrats on the new purchase. Didn't know you had crashed the previous SLK.

Two thoughts. On my old SHO the variable intake runners could be disconnected. You could tell the difference, but it was subtle, not dramatic. Mostly the lack of a switchover to the short runners at the designated rpm. I don't think a malfunction there is going to cost the kind of power you are missing.

Second. Not sure a 320 is much faster than a 230. It's approximately 215hp vs 190, and it weighs a bit more. More refined for certain, which of course makes it feel slower. So you may have to adjust expectations accordingly. That said, it definitely sounds like there is something to be chased down in the new car. Good luck.
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Old 10-08-2016, 09:30 AM
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The HP curve matters more than peak HP. I'd expect the smaller displacement engine to have more of a peak even with forced induction. ( less low speed power )

Was this car a garage queen? I've seen more than one seldom driven car with the air filter box filled with dog food. . . and I'm picturing a skinny dog in the corner.
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  #11  
Old 10-08-2016, 07:43 PM
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Originally Posted by 97 SL320 View Post
The HP curve matters more than peak HP. I'd expect the smaller displacement engine to have more of a peak even with forced induction. ( less low speed power )

Was this car a garage queen? I've seen more than one seldom driven car with the air filter box filled with dog food. . . and I'm picturing a skinny dog in the corner.
I had a similar thought - physical restriction of the air intake path acting as a throttle.

It's been a long time, but I have hazy recollections of the supercharged m111 outperforming the 2.8 liter m104 despite a lower peak hp. But the m112 has quite a bit more power than the smaller m104. I'd expect it to outperform the slk230, but I don't think the margin of difference would be all that large.
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  #12  
Old 10-09-2016, 11:44 PM
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Thanks for all the replies. I did indeed get this car for a very good price. I was happy to buy the car for that price even with the known shortcoming

The car is a long way from me, so I did not have the options that you would hope to have with such a purchase. I expect to go get the car Tuesday or Wednesday. I expect to get to the bottom of the problem then.
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  #13  
Old 10-10-2016, 12:10 PM
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Quote:
Originally Posted by Ferdman View Post
Air&Road, if the mass air flow sensor is bad the Check Engine light should be lit......
The CEL will light up only when the fuel trim correction reaches it's limit. This is why symptoms can appear before the light comes on. A proper diagnosis would include checking the fuel pressure and monitoring the air mass value while under hard acceleration
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Old 10-11-2016, 06:48 AM
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Air&Road, other possibilities would be a dirty fuel filter or restricted fuel lines. Best to follow ILUVMILS's advice instead of guessing and throwing parts at the problem.
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  #15  
Old 10-12-2016, 06:46 AM
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I have done lots of engine performance troubleshooting, so once I get it home, give it the once over and connect a scanner, I will get to the bottom of it. My reason for starting the thread was to probe into what known or common problem might exist with the breed.

I go get it tomorrow and will report what I find. Can't wait!

Thanks very much for the responses.

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