Hi all,

I just picked up my 1999 SLK230 R170. Really loving it, but as I've seen with several other posts, putting the foot quickly to the floor results in the car spluttering, whilst gradual acceleration is fine. The supercharger is functional, however I have had diagnostics run which shows the following:

View attachment 593262

Can anyone with experience of this issue let me know if a reset of the flap will fix this or if I should be replacing parts of the module?

Thanks!

Hi
It maybe time for a new flap it's always worth trying to reset it if you have the facility to do so. However it is unlikely to be a permanent fix these flaps don't go wrong too often but they are known for going bad.

The misfire one 2 and 4 is a interesting one the reason for this those cylinders are both on separate coils, 1-2 on one coil and 3-4 on another coil

One thing I should ask am I right in thinking this is a pre-facelift car Im just guessing by the model year.
Also is the car modified in anyway, Supercharger pulleys or any intake modifications? The reason I ask this is the MAF sensor can cause boost issues on these.

Also does the car rev past 4k or is it limited?
A lot of questions I know but it just help figure it out a bit better.

The reason I wonder if the MAF could be at fault is the fact you have both codes for multiple misfires on separate coils and your having boost issues. When ever we have had the MAF fail we have had very similar issues and the fact you also have a code for the mixture. Which says the engine is having trouble trimming the fuel to the airflow. Again sometimes when MAF's fail they do trigger O2 sensor codes.

 

Hi Alex. Thanks for taking the time to reply - that's what I initially thought may be the case RE the flap.

The car is pre-facelift, completely unmodified however I have not actually checked that it will rev higher than 4k rpm, will do so this evening. I'd assume from several trips on the motorway up to 90mph that it can though.

So we can likely say that this issue will either be with the flap itself or the MAF? Looks like I've got a bit of trial and error ahead of me!

 

No worries always happy to help on M111 stuff.

It's hard to determine which it is the reason I say that is if the flap failed and stays shut it would cause a "overboost" situation topping out the MAF causing it to cut the spark.

However it your not feeling any boost then the flap is likely in the open position or "failsafe" position which is the default position for when the MAF fails. It does this to prevent unmetered boost entering the engine as without the MAF the car can not calculate the fuel needed for the airflow.

Also if your car is auto you will need to drive it to see if it will rev over 4k due to the stationary limiter on some Mercs. I can't actually remember now if they still had it up to 99 but I think they did.

Price wise a good used flap normally is around £30 on fleabay so not the end of the world if it is that.

However I think a MAF is around £150-180 also these cars tend to only like genuine Bosch In my experience, when I tried cheaper sensors the car didn't like them and the fault in one form or another remained. I am not the only one to have this issue with aftermarket sensors either it seems a common theme on here.

The biggest issue faced is knowing for sure it is the MAF causing it before spending the money. Now it is fairly easy to remove maybe worth just giving it a visual inspection, as the cam cover breather vents oil and carbon into the post filter side of the air box causing oil to be drawn through the Supercharger intercooler and the MAF coating everything bin a good film of oil.

Hope this is some help buddy 🙂

 

UPDATE: Took MAF out and found a fair bit of oil. Just sprayed generously with isopropyl alcohol and will put back later tonight once dry to see if this rectifies the issue.

For anyone following in the future, refer to this video to remove the MAF - very easy to do.

 

Got my fingers crossed for you buddy. One thing we have learnt to do if your handy with the spanners is when the car isnt going to be in use for a couple of days (this applies bro kompressor cars only) is to whip the front bumper off get the intercooler out and give the inside a good soak with brake cleaner, then leave it up on its end over night to dry out and make sure It is thoroughly dry before refitting. We do this to all our kompressor cars well the ones we don't fit Turbo's to 😂.

The biggest problem with the intake is the way the cam breather recirculates. The little swirlpot bolted to the cam cover does work alright but over time gets clogged and the oil no longer drains down, instead along with the gasses from the cam cover it goes straight into your air box post filter directly under the intake pipe.

We combat this by just fitting a catch can but equally to keep it stock the swirl pot drain thingy (the professional term 😉) can also be cleaned with brake cleaner or just replaced with a new part. It's a good thing to do when buying any pre facelift M111 Kompressor car.

 

It is a little like learning a new language at the moment ! That sounds like something I'd be able to do though, luckily working from home so no issues with keeping it out of use for a few days. Will give it a go thanks mate!

 

I would also clear all codes first, and then see if that Misfire on # 4 Cyl comes back, if it does then it is a genuine Fault and not an old code

That Cyl # 4 code shows as current, could be a Spark Plug or bad Coil, Air flap also shows as current, so yep as @Alex.M-oneeleven correctly says look into that as well

It is worth fitting brand new NGK Plugs from a reputable source

HTH

 

Good thought Dave definitely clear codes first if you have the facility to do so, to make sure what is there is current and not old.

That's something I've been meaning to ask you Dave aswell as you recommend NGK I've been thinking about this as a lot of the Honda guys use them. We have always used Bosch plugs, what's your experience with Bosch compared to NGK?

 

I only use NGK, have never really compared them buddy

I'm told Bosch are OK, MB OE is Bosch or NGK, I've only been buying NGK ever since I started working on V12 Jaguars eons ago

Here is a couple that came outta my V8 Engine in my SLK when I first bough the Donor Car with full MB History .......................

clickable ....





Notice that the NGK's Electrodes above are way more worn than the Bosch below ....





.... which of course is categorical proof that that particular stealership, (and many others are robbing theiving no good lying wotsits who charged the previous owner for replacing 16 spark plugs but only replaced the NGK (original from it's build at factory) Plugs that were easiest to get at

 

Cheers Dave that is a useful comparison, I must admit when I did the plugs on my 430 I wanted to shoot myself but still did all 16.

Sadly there's too many places out there that will be happy to do half a job the same thing happens with the older smart cars the lower row never gets changed just because it's a headache to do.

One brand I'm very curious about are the brisk racing plugs they're a very interesting and unique design. I may try a set on the clk as it need some however due to the design they are fixed gap, which isn't ideal especially when the car has altered ignition but we'll see.

They produce quite a few variations of these type of plugs, not sure how well old school coils would cope with this type of plug though.

 

I'll be interested to find out how they react, but I think on an M112 / 113 they would upset the ECU's multi-spark function and pop misfire codes due to the Ionic Current Monitors

 

Ide be inclined to agree with you on that one also the extra sparks per cycle on a multispark system not sure if that would be good or bad. I almost think that it would change the flame kernal too much so the ignition would essentially loose all pattern and just be a ball of boom 😂. Rendering the multispark aspect of the ignition unusable.

I dunno I'm not gonna try be too clever here cause I'm not, but that would be my way of looking at it I'm still learning to fully understand this side of things to try and improve my engine building skills.

 

I almost think that it would change the flame kernal too much so the ignition would essentially loose all pattern and just be a ball of boom 😂. Rendering the multispark aspect of the ignition unusable.

I agree

 

UPDATE: Just refitted the MAF sensor after cleaning, and I'm astounded - it's a completely different car. I can put my foot down hard to the floor and where before it would splutter, it now either downshifts or accelerates without issue, and appears to be holding onto gears a lot longer.

It feels like the first time I'm hearing the AMG exhaust properly and I'm amazed such a small fix could bring the car back to its former glory. Many thanks to @Alex.M-oneeleven and @Dave2302 for their input

 

It feels like the first time I'm hearing the AMG exhaust properly and I'm amazed such a small fix could bring the car back to its former glory.

I'd be kinda surprised if it had an "AMG exhaust". In any case, marked as resolved BUT if the problem resurfaces, please return to THIS thread (do NOT create a new one) and we will update accordingly.

 

Super I'm so glad it sorted it for and without costing much if anything if it happens again ide recommend a new MAF but extremely pleased to hear it's fixed buddy 😃

 

Maybe. Maybe. And maybe he added it ?

Ask for your free data card and know for sure -->as it came new from the factory 😉

Vehicle Data Card

Post your VIN & get your Data card

www.slkworld.com

AND have a read here about "1999 SLK230 AMG"

1999 SLK230 AMG myth or not

Hi i recently purchased a 1999 SLK230 and it has an "AMG" on the rear. Yes i know there were no AMG motors in 1999 but there appears to be some reference to AMG cosmetic upgrades. So what do i have. well i know i am the 3rd owner and that the 2nd owner upgraded the grill. (i know this...

www.slkworld.com

 

We had a AMG spec W202 few years ago we got the options bloat from Mercedes and sure enough that's how the first owner ordered it. However it is rare to find cars with AMG options that actually came like it from the factory but still I'm sure that sounds much better than the stock 230k exhaust 🤣

Just checked the papers the previous owner gave me with it and it's fully specced! He said he hadn't added anything to it when I picked it up - I'm only the second owner!

 

We had a AMG spec W202 few years ago we got the options list from Mercedes and sure enough that's how the first owner ordered it. However it is rare to find cars with AMG options that actually came like it from the factory but still I'm sure that sounds much better than the stock 230k exhaust 🤣

 

Still, get your data card! It's free ya know

 

Great to see you've fixed it

 

Sorry to join the party late, but a few years ago I had similar issues with my old W210 E Class and was advised to run a few tanks of Shell V-Power through it and stay away from Supermarket fuel. I never had a repeat of that problem again and still only use V-Power in my MBs.