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1996 S500 & 1997 SL600 & 2013 C300 4Matic
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Discussion Starter #41 (Edited)
I've read this entire thread and you guys are amazing! I just got a 95 SL600 with 113K miles. I have 3 wiring harnesses, hydro spheres,, and maybe a MAF to replace, but that all sounds simple compared to what you guys are dealing with. What equipment do use for diagnostics and where should I get it? There seems to be something available from Hong Kong and then StarTeckInfo. How do they relate? What do I need? Thanks.
Welcome to the thread, spud06! What you will need is a Chinese clone of the Mercedes Star Diagnostic System (SDS) hardware and software. Specifically, and this is very important, you need a version of the SDS software that was built before Sept 2015. The reason is that from that point on SDS no longer included HHTWin, the Windows emulation of the old Hand Held Tester (HHT) that was originally used by MB techs to diagnose our cars, and is necessary to diagnose them. The software is usually shipped on a SSD for installation on specific, discontinued laptop computer models. For instance, my software was delivered on a SSD for a Dell Latitude D630 laptop PC, of which I was able to purchase a refurbished unit on amazon for small money. On the hardware side, you will need a C3 (wired) SDS multiplexer box with a cable terminated by the MB 38-pin connector to plug into your car's diagnostic port. You probably know by now that your car does not have an OBD2 port. You may be able to buy the hardware and software separately, or bundled into a complete kit that includes the PC to run the software. I bought my software, hardware, and PC separately since I could not find a bundle that included the pre-9/2015 software. I bought the hardware and software on aliexpress (Chinese equivalent of amazon). Don't skimp on the hardware quality - purchase one of the more expensive models to avoid configuration issues. I found advice on another thread to buy a model with the word "super" in it, and that is what I did, and I haven't had any issues whatsoever. Good luck and welcome to the R129 club.

Edit: Corrected year of deletion of HHTWin from SDS software and my laptop model.

Tom
 

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1995 SL600
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Thanks Tom for the info. I'm trying to get a smart start on this project. The definitions help. I hope the cost of admission to this "club" won't break me! Much to learn. I'll look for the thread on the SDS clone. Thanks again. Perry
 

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1996 S500 & 1997 SL600 & 2013 C300 4Matic
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Discussion Starter #43 (Edited)
Thanks Tom for the info. I'm trying to get a smart start on this project. The definitions help. I hope the cost of admission to this "club" won't break me! Much to learn. I'll look for the thread on the SDS clone. Thanks again. Perry
You're following in my footsteps, Perry, and those of many other forum members who have gone before. This forum is your best resource!

BTW please see my edits to my first reply to you above before you make any purchase decisions. I was working from memory in my original post, and apparently my memory is not what it used to be!

Cheers
Tom
 

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97 SL600 Pano, ex: 96 (late 95) SL320
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A FPR leaking gas into the vacuum line has a ruptured diaphragm and should definitely be replaced. The caveat is this may or may not solve your problem. In my case, replacing a leaking FPR with a good one on my S500 made no difference - the engine ran well both before and after.
Well, looks like I didn't get lucky. The problem still persists. Time will tell if this made a difference to the occasional warm start weirdness I described before, but the idle fluctuation and vibration are still there.

Here's a video a I shot just a while ago:
. Usually the fluctuation is barely visible on the tach but it definitely feels inside the car (although the new engine mounts made a huge difference).

What else might it be? I'm starting to think injectors, but I'd still like to rule out other possibilities first. One thing I'm wondering if any of the belt driven auxiliary devices might cause this. It shouldn't be the AC compressor as having the AC on or off (or EC mode) makes no difference. Could the ADS be doing something all the time, causing load to the tandem pump?

I replaced the spark plugs recently (Bosch F8DC4) and as mentioned before in this thread, all the boots and coils were replaced about a year ago.
 

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Discussion Starter #45
Well, looks like I didn't get lucky. The problem still persists. Time will tell if this made a difference to the occasional warm start weirdness I described before, but the idle fluctuation and vibration are still there.

Here's a video a I shot just a while ago:
. Usually the fluctuation is barely visible on the tach but it definitely feels inside the car (although the new engine mounts made a huge difference).


I replaced the spark plugs recently (Bosch F9DCO) and as mentioned before in this thread, all the boots and coils were replaced about a year ago.
Juuso, that slight fluctuation seen in your video really doesn't look like much of a problem to me, but I will take your word for it that you feel it much more in the seat of your pants. It looks to me like a throttle body is fluctuating a little at idle for some reason, and I suppose if only the throttle body for one bank is doing this, it could cause an imbalance that makes the whole engine vibrate. More generally, it could be that one of the sensors (MAF or MAP perhaps) on one bank isn't working properly, causing the imbalance. Your car isn't producing any fault codes at all when this happens? If you look at actual values for these sensors when the vibration happens, do the sensor values agree? Do they differ from when the car is idling normally?

Also, you wrote that you replaced your spark plugs with F9DCO, which are indeed the correct replacements as specified in our manuals, but my understanding is they have been out of production for many years. Where on earth did you find them?

Tom
 

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Oh sorry, I meant F8DC4 of course. I'll update the original post.

No faults and no other symptoms. I'll have to take another look at the actual values one of these days. I haven't spent a lot of time staring at the diagnostics recently, but maybe I should try again and see if I spot something.
 

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Due to the stubborn idle issue and because of some oil I found in the spark plug wells, I decided to pull the intake manifold and the valve covers. I'll probably post more details on that job in a new thread somewhere (possibly elsewhere as I'm getting frustrated with the "brain leak" the forum upgrade has caused as some valued members have left).

Anyway, I had the injectors tested and they all checked out, no problems at all. Then I pulled the intake and valve covers and took them to be powder coated. While waiting for that, I pulled the crankcase breather pipe from the V valley. And what do you know, the plastic pressure damper part was cracked. It leaks, and it's quite likely to be the cause of my idle problem. Good ol' unmetered air.

The damage is pretty obviously external, and I'm 99% sure it's been caused by someone forcing the pipe down in the valley past the heads. It took some wiggling to get it out, too. It's really puzzling, I can't imagine why someone has been down there before. All the parts with date stamps seem to be originals, i.e. nothing I've found was newer than the car.

It'll be a couple of weeks until I get the new part (+ some coolant hoses I overlooked before) but I'll report back once it's all back together.

IMG_1881.jpeg IMG_1883.jpeg
 

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Discussion Starter #48
Juuso,

Thanks for the update, and please do post your future updates to this thread, because I for one am very interested in the outcome. I've had my car for two years now and have yet to pull the spark plugs, partly because I am dreading what I will find when I do it, like oil in the wells as you did. The reason for my dread is the size of the job, not just the valve cover gasket replacement itself, but all the other "while you're in there" jobs you can find discussed in other threads on this forum - breather pipes (as you are doing), knock sensors, crankshaft position sensors, timing chain guides, etc.

I look forward to reading about your progress. Sadly my own SL600 is in storage now until April :(

Best of luck
Tom
 

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I posted more details about the job in another thread. As mentioned there, the idle problem didn't get solved. But today, I think I finally had a breakthrough.

I recently got a fuel pressure tester, and today I checked the pressures. All good - 3.2 bar with and 3.8 without vacuum at the fuel pressure regulator. A little on the low end of the acceptable ranges, but still acceptable I believe. After that I hooked up the SDS and did a bit of investigation. First I wanted to check what the MAP sensors think when I disconnect any vacuum hoses and plug them with my finger temporarily. Nothing out of the ordinary came up.

Then, I took a look at the "smooth running" values, and was surprised to find that the right bank showed a near-constant 0 while the left one was fluctuating, many cylinders going above 2 1/s^2 occasionally. For the first time, I saw actual data pointing somewhere. The next step was obviously to start swapping components from one side to another. First MAFs, nothing. Then throttle bodies - BINGO! The uneven running moved to the right bank.

It's kind of weird that such a difference between the banks wasn't visible before. I think fixing the vacuum leaks (FPR and crankcase ventilation) may be the reason to that.

Next up, trying to figure out what's wrong with the throttle body. In yet another thread.
 

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Discussion Starter #50
I posted more details about the job in another thread. As mentioned there, the idle problem didn't get solved. But today, I think I finally had a breakthrough.
Thanks for the update, and congrats, I agree it sounds like you're making real progress now. You'll probably have your problem sorted soon.

When I was debugging the rough running issues with my SL600 that prompted me to start this thread, like you I also encountered the situation that frequently fixing one problem would reveal new problems, until I finally solved the last one and it all worked fine - or almost, as I still have a mysterious intermittent vacuum leak that triggers the CEL, but doesn't seem to affect performance. In particular, replacing all my old, brittle vacuum lines exposed a lot of problems. One of which was a bad ignition coil, which I diagnosed by swapping it with the coil on another cylinder and watching on SDS to see if the fault moved - it did. SDS is a real godsend for diagnosing these problems!

Best of luck
Tom
 

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I posted more details about the job in another thread. As mentioned there, the idle problem didn't get solved. But today, I think I finally had a breakthrough.

I recently got a fuel pressure tester, and today I checked the pressures. All good - 3.2 bar with and 3.8 without vacuum at the fuel pressure regulator. A little on the low end of the acceptable ranges, but still acceptable I believe. After that I hooked up the SDS and did a bit of investigation. First I wanted to check what the MAP sensors think when I disconnect any vacuum hoses and plug them with my finger temporarily. Nothing out of the ordinary came up.

Then, I took a look at the "smooth running" values, and was surprised to find that the right bank showed a near-constant 0 while the left one was fluctuating, many cylinders going above 2 1/s^2 occasionally. For the first time, I saw actual data pointing somewhere. The next step was obviously to start swapping components from one side to another. First MAFs, nothing. Then throttle bodies - BINGO! The uneven running moved to the right bank.

It's kind of weird that such a difference between the banks wasn't visible before. I think fixing the vacuum leaks (FPR and crankcase ventilation) may be the reason to that.

Next up, trying to figure out what's wrong with the throttle body. In yet another thread.
It's like we are working on twins! I replaced one of my throttle bodies 48 hours ago!
I had error P1580 (Right Actuator), swapped the TBs and after 24 hours got error P1581 (Left Actuator)! Bingo, thankfully I already bought a TB from Ebay that arrived the same day! But still I can't get the smog test done here in California...
 
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