SLK230 runs rough / pulls timing - Mercedes Benz SLK Forum

SLK R170 General Discussion SLK 200, SLK 230K, SLK 320, SLK32 AMG

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#1 Old 2 Days Ago
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SLK230 runs rough / pulls timing

1998 SLK230 Kompressor


The car runs and drives. However, when it is hooked up to a scan tool and I see the live data, I can see that it is pulling timing. It is about -12 at idle and around -30 when accelerating.



Things that I have done to try to address:
--Camshaft Adjuster Magnet
--Camshaft Position Sensor
--Fuel Pressure Regulator
--MAF cleaning
--Cleaned engine grounds
--New Spark plugs, wires, and coil packs


Both long and short-term fuel trims are great--all within +/- 3%


Any ideas as to what I should look into next?
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#2 Old 2 Days Ago
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Isn't advancing the ignition and camshaft timing at higher rpms normal? If you are chasing a real problem what is it?
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If it would be advancing the timing, it would be a positive number. On ever other car I have (Audi, Acura, and Toyota) it is a positive number. This is especially true when accelerating. This car is 'pulling' timing and going in the wrong direction.
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Basically, I am concerned that the ignition is happening ATDC (as opposed to BTDC, as it should be).


However, I am new to this car. I also know that this vehicle has a 'wasted spark' ignition system because 1 coilpack fires 2 cylinders. Perhaps that is what I am seeing?


In short, if it is pulling timing, because of knock or some other failure, I would like to get it fixed. However, I do not want to chase ghosts if that is just how it is because of the 'wasted spark' system.
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Anything I've read in the last few minutes courtesy of Mr Google all suggest coil (pending) failure.


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I was hoping that it was going to be coil failure. When I changed them out, I noticed that one of the coilpacks was newer and one was original. I had high hopes when I started it up after changing out the ignition system!
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Check it with a timing light? Question: Does it run rough always?
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Originally Posted by efair View Post
Check it with a timing light? Question: Does it run rough always?

How would I do that? I figured the timing would be adjusted by the ECU.


It seems somewhat okay while it running. I bit more vibration than what I would think would be normal. The most noticeable time would be when the car is turned off--it seems to flop over one last time.
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That is actually an excellent question - I'm not even sure you can. I think you can, but without one in the driveway I can't say for 100% sure. The fact that your car runs as well as it does makes me think you're looking at a reporting anomaly here, not an actual problem with your timing.

There are timing marks on the crankshaft pulley and timing cover; with an old school strobe-style timing light you 1) connect two clamps to the battery and a third inductive clamp around the #1 plug wire, 2) start the car, 3) point the lamp at the pulley, 4) pull the trigger, and 5) look at the marks - which are frozen in their relative position to one another, disco-dancing-style, by the strobe. It's a lot easier to do than to describe. And if you've not been to the disco before, here's a video of @Berliner Heckflosse demonstrating from his younger years: https://youtu.be/aC-d2VckqUw

The only question is "is there enough room to get the inductive clamp around the #1 plug wire". IDK.
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Folks. Timing ADVANCE is BEFORE top dead center

this equals a negative number.

your numbers are fine!
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#11 Old 1 Day Ago
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Originally Posted by Turdo2 View Post
Folks. Timing ADVANCE is BEFORE top dead center

this equals a negative number.

your numbers are fine!

I did some more research, and in short, you are correct.


For the benefit of anyone else who comes across this thread, I will expand on this further.


In the early days of ODB2, some vehicles (most of the examples I found were Mercedes and GM) reported the timing advance data differently then what many do now. The PID that these apps use is translated as a negative number instead of a positive number. So, a -30 in my older Mercedes is similar to the 30 that I see in my newer Audi. It basically comes down to the data that the ECU is giving and how the app is reporting it.



If one is still concerned that their engine is retarding timing, a better test would be to look at the knock sensor data. If the engine is indeed massively pulling the timing, one would see a ton of readings from the knock sensor. If there is an air/fuel issue, one would probably see it in the STFT (Short Term Fuel Trim) and the LTFT (Long Term Fuel Trim). Without getting too far into the weeds on fuel trims, numbers of +/- 5 mean the engine is running great. When the numbers get higher than +/- 10 that means that the ECU is compensating for something (minor, at this point). Most cars will throw a rich/lean code when the readings are more than +/- 30.



All that being said, I will be updating my Crankshaft Position Sensor just so the ECU has good data when adjusting the timing. It has never been done in my 21 year old car, so I figure it cannot hurt. In my SLK230 (and I suspect most R170s) the timing is set based on the info that the ECU receives from the Camshaft Position Sensor and the Crankshaft Position Sensor.
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Hi,

I have always written it and read it that any figure quoted zero is TDC, therefore 10 is 10 ATDC (retarded) and -10 is 10 before TDC (advanced)

HTH, Cheers Dave
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Originally Posted by Dave2302 View Post
Hi,

I have always written it and read it that any figure quoted zero is TDC, therefore 10 is 10 ATDC (retarded) and -10 is 10 before TDC (advanced)

HTH, Cheers Dave

And you are not wrong. And if the only car you have ever hooked up to these apps (Dash Command on iOS and Torque on Android) was your Mercedes, then you would be used to the data being presented in that way. These apps present it as timing advance so a 10 is technically 10 degrees BTDC. Which, as you pointed out, is -10 degrees in respect to the engine.


I am new to the world of Mercedes-Benz, but I am not new to cars in general. This was the first time I had seen the data like this and thought the car had a massive timing issue. Perhaps my post/experience is common knowledge to you, but it certainly was not to me. My hope is to help those that use these phone apps on their car, and are new to vehicles that present in this fashion.


Thank you everyone for your input. I has been much appreciated!
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Hi @darksider15,

There was no offence intended in my post, I was just agreeing with your conclusion.
Apologies if it came across like that, I'm just one of these guys who says things bluntly as they are.

What I'm actually saying is that Cheapish Apps, OBD plug ins, Hand Held OBD Scanners etc etc are incorrect, which is yet another reason as a Diagnostic specialist business I will always advise they are not the best thing to be using.

Anyone with a Mercedes-Benz who is serious about DIY should get a Ł400 SDS system, good advice as others who have trodden that path will testify.

NOTHING else within that price bracket will come close to accessing the same info and data etc, SDS acesses everything, and has a ton of other features included.

Missing vital info often leads DIY'ers to wrong conclusions and costs them money on parts they don't need

Hope this clarifies,

Cheers Dave
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Originally Posted by darksider15 View Post
How would I do that? I figured the timing would be adjusted by the ECU.


It seems somewhat okay while it running. I bit more vibration than what I would think would be normal. The most noticeable time would be when the car is turned off--it seems to flop over one last time.
Hi again

Have you checked your Engine Mounts and Trans Mount, they can look perfectly fine but be absolutely FUBAR

HTH, Cheers Dave
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Quote:
Originally Posted by Dave2302 View Post
Hi again

Have you checked your Engine Mounts and Trans Mount, they can look perfectly fine but be absolutely FUBAR

HTH, Cheers Dave

I have not checked them, but they were all replaced less than 20k miles ago.
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