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Discussion Starter #1
Hi Folks,

I have a sudden and weird problem with my 2001 SLK 230, manual transmission, ~82K miles on the clock. Yesterday I was driving, and had to make a jerky movement as someone pulled in front of me. Immediately the car seemed to lose power. The harder I pushed the accelerator, the more sluggish the car became. I pulled over and looked into the engine compartment, but found nothing obvious. Having just left home, I returned and went out again in my other car.

This morning I took a closer look. One symptom is if I have the car idling normally and then floor the accelerator in neutral, it takes about 3 full seconds for the engine to hit the 4000 RPM rev limiter, and it takes a good 1.5-2.0 seconds for the engine to respond to the floored gas pedal. Normally, response to the gas pedal is near-instant. While driving it around the neighborhood, there were moments where it seemed almost normal, but then it bogged down again. I'd note that beyond the incredibly sluggish accelerator response, the engine seems to be running fine. It's smooth and sounds completely normal.

In terms of background, I had previously had a problem with the waste gate solenoid, but after I cleared the codes and re-adapted the waste gate, that problem disappeared. However, I suspected this might be part of today's problem. So I unplugged it and tried to run the car. But it made no difference.

After that, the CEL came on, and I read the codes, which I note below:

P0247 (current and pending, e.g., 2 of 5 codes shown) - Wastegate solenoid malfunction. I had seen this code with my prior problem and believe its presence is due to my having unplugged the wastegate solenoid.

P0410 SAI System malfunction, SAI is secondary air injection. I also think this is due to my having unplugged the wastegate solenoid, but am willing to hear otherwise. I think (but am not 100% certain) that I saw this code with my prior wastegate problem.

U3FFF, pending -- I have no idea what this is, perhaps an artifact of my cheap-o code reader.

P0120 TP Sensor circuit A malfunction

That last code is what made me think that perhaps my throttle pedal with its associated position sensor might be the problem. I've removed it from the car and probed the 6 connections with an ohm meter while moving the pedal, but my readings are inconclusive. If it were a combination of 2 potentiometers, I'd be able to tell if there are dead spots via the ohm meter. But I've done some reading, and some of these pedals have a hall effect sensor inside and so aren't amenable to simple resistance measurements. I'd also note that while the car has fairly low mileage, those miles are mostly city driving, lots of stop-and-go, and so the accelerator pedal could well be worn beyond its years.

After I read the codes, I reconnected the wastegate solenoid and cleared the codes. I then drove around my neighborhood again, and the problem had not changed. Nor did the CEL re-fire. I suppose I could try to drive it farther to see if I can get the CEL light to come back on, but it's frankly a little nerve-wracking to drive this thing with a super-sluggish throttle response and much less than normal power.

Any suggestions would be MUCH appreciated.

Thanks,

Kim G
Boston, MA
Where it seems to be cranky Mercedes month.
 

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Discussion Starter #2
OK, sometimes the prime directive of a Mercedes is to make the owner look as foolish as possible.

In the bizarre update department, just after writing my post above, I reinstalled the gas pedal so I could at least put the car back into the garage. Well, the car fired right up, and the engine seemed more responsive than it had been. So I took it for a spin around the neighborhood, and now it's working fine.

I suspect there may be some junk inside the gas pedal assembly that got moved out of the way when I took it out and tested it.

Still, I suspect there may be a new gas pedal in my future. Or not, depending on the whims of the Mercedes gods. For those of you who may not know, "mercedes" means "mercies" in Spanish. So let's hope that mercy is what I get.

However, I'm still interested in hearing other theories from anyone reading this.

Thanks and have a great day,

Kim G
Boston, MA
Where we're now wondering whether we have the nerve to take the 25 mile trip we had planned yesterday.
 

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Administrator 2009 SLK 55 AMG/Founding member 2006
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94,192 Posts
throw some of this in there:



and reset this:

 

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Super Moderator UK 2002 SLK320 Blue
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Hi @El_Murcielago The gas pedal is a spring-operated magnet-and-hall sensor so there should be no moving parts to wear out or potentiometers to fiddle with. (see attached)

I had this issue a few years ago and took the pedal out, cleaned it up and put it back - funnily, I've had no futher issues with it!

Hope the attached helps you understand how it works.
 

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Discussion Starter #5
@jbanks15, Thanks for the suggestion. Though it was a few months ago, it wasn't many miles ago that I drove that car from California to Boston, via El Paso, TX. It performed flawlessly the entire time. Moreover, I ran a few bottles of Techron through it during the journey. So I rather doubt it's fuel, especially given the near-instant onset of the problem. But thanks again for the tip! Cheers!

@savcom - Thanks a bunch. After I wrote the second post, I drove the car about 50 miles or so, and it performed perfectly, maybe even better than usual. So I'm a bit stumped. But thanks for the info on the pedal. Hopefully my taking it out and putting it back has shaken loose some dust or something. I'm just wondering whether I should worry about this recurring or not. Your post suggests maybe not. I'm crossing my fingers. Thanks again!
 

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Discussion Starter #6
@jbanks15 P.S. It's a manual transmission, so there's no transmission to re-adapt. But one of the things I did do before removing the gas pedal was to re-adapt the gas pedal, instructions for which I found elsewhere on this site. But it didn't do anything. Only after I put the pedal back did it work again, and even then, I didn't do the re-adaptation a second time, e.g., when I reinstalled the pedal, I just fired it up and it worked. So file this one under "puzzlers." Cheers.
 

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Registered 2001 SLK320
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Seems that this is sorted but I have been around to see many times folks take carpets out or in an emergency carpets which are not fastened down and they foul the gas pedal. Just last week at a car wash I watched a guy dump his carpets while waiting. When he started his car revs were up and he nearly put the car through the door.
He had put his carpets in wrong and when he put his foot down the first time carpet wedged between the trans tunnel and pedal. I have seen it do the opposite as well and prevent pedal travel.
 

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Discussion Starter #8
Hi Alex, Thanks for the reply. I'm pretty confident it's not carpet. But you never know, right? Sometimes it's the simplest things. In any case, I'm keeping my fingers crossed that this was a one-time, freak problem that will never, ever return.

Cheers,

Kim G
Boston, MA
Where we're embarrassed at how many times it is indeed something as simple as a stuck carpet.
 

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Super Moderator UK 2002 SLK320 Blue
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Only after I put the pedal back did it work again, and even then, I didn't do the re-adaptation a second time, e.g., when I reinstalled the pedal, I just fired it up and it worked. So file this one under "puzzlers." Cheers.
Let me suggest that by making and breaking the plug contact between the pedal and the rest of the car when you took it out may itself have cured your problem. I did give mine a quick workover with a dose of contact cleaner and a cut-down wooden coffee stirrer before putting it all back. Just a thought.

571944
 

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Registered 05 SLK55 & 06 Kleemann 55K S8
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It was probably the bypass valve (aka BOV) stuck open. That will bypass air and cause the exact symptoms you are talking about. You were basically running around NA. I am guessing this is what you were referring to as the wastegate.
 

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Discussion Starter #11
@savcom - thanks for the help on my problem. Beyond hooking up an ohm meter and trying to make sense of the readings, I did nothing to the gas pedal. Indeed the contacts looked fine. But taking the pedal out may well have forced the system to re-adapt the pedal on its own. Who knows? It was fine for my 50 mile trip yesterday, but I'd be lying if I didn't admit to some concern over recurrence far from home. Yeah, the car would be driveable, but a bit of a hazard.

In any case, thanks again.

Kim G
Boston, MA
Where we seem to have a stable of cranky machinery -- SLK, C280, Toyota truck, and various other bits of aged machinery.
 

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Discussion Starter #12
It was probably the bypass valve (aka BOV) stuck open. That will bypass air and cause the exact symptoms you are talking about. You were basically running around NA. I am guessing this is what you were referring to as the wastegate.

You know, that was my first guess, but disconnecting the wastegate solenoid had no effect on the problem. Only removing and replacing the gas pedal seems to have solved the problem. But as I've noted above, I'm not exactly 100% confident that I've fixed the problem for good. But I have my fingers crossed.

Cheers,

Kim G
 
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