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Discussion Starter #1
OK apologies in advance for the following "War & Piece" like post, but have been trying to diagnose this problem for almost a year now, so thought it best to be thorough and include all the info I've gained.
Bought a 1999 SLK230 Auto (UK Spec) Aug 2018 62k miles on the clock, runs well but......from early on I noticed that if you kicked it down hard it would splutter and wouldn't rev over 3200rpm (ish), didn't use the car all the time so it got left parked up for a while, then when I used it again noticed that sometimes it seemed to rev up passed the 3.2k mark OK but seemed down on power, I needed to do an auto transmission fluid change, so did that early this year, gear change is fine but has made no difference to the original problem, so I cleaned the MAF sensor, had the Cam Adjuster Magnet out and checked it (as far as I can with a meter) and seems to be OK, checked the Supercharger is spinning up as the clutch engages as 2000rpm OK. had the Supercharger bypass (air recirculating flap) off checked and it seems to be closing (if fluttering a bit?) So I fitted a cheap & cheerful Boost Gauge to the car to see if there was actually any boost pressure? This has revealed two scenarios : - Sometimes under moderate to hard acceleration you get about 4-5psi boost up until about 3200rpm then again as described earlier it will splutter and misfire until you back off the throttle, then it runs smooth again, But sometimes you get no boost at all and it will then rev all the way up to 5000rpm+ with no problem, but with a very noticeable power loss? These two scenario's tend to happen on different days not within one trip?


The car does NOT have a standard OBD2 plug, only the older Merc 38pin round connector (I have looked extensively) but I managed to get a garage with a "Launch Tester" that had a 38pin adaptor to check and the only codes that had been logged are: - P0170-22 Part Throttle Self Adaptation at limit value(a61) - P300-80, P301-81, P303-82, P304-83 all Cylinder Misfire codes. and finally P0243 Air Flap Switchover Actuator for Compressor M16/7. I'm not getting a check engine light up at any time, but I find that if you continue to push it when it starts to splutter on kick down it will go in to limp mode, which always resets OK if you turn the engine off & on again?


Anyway I'm now a bit confused re what to start replacing first i.e. Air Flap, Cam Mag Adjuster, MAF sensor, or even cam position sensor? and hoping not to replace all and still have the problem...…………..any suggestion would be helpful?
 

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Discussion Starter #6
OK Fuel pressure seems OK, (around the 40psi mark?), still very puzzled why it has the two different scenarios?, seems to me that when it's on boost it's failing to rev past 3200rpm due to either fuel starvation or over fueling or possible valve timing so still think it may be something to do with the Cam Magnet, but think this could also be down to the MAF sensor. But then why sometime would the Air Flap not close, I'm guessing that's the reason for "No Boost" on some occasions, but does suggest that that as when this happens it runs and revs smoothly (apart for lack of power) that it can't cope with the boost pressure and is not adjusting fuel injection or valve timing correctly?
Most Cam Magnets I've seen seem to work by adjusting the Oil flow to the Cam shaft adjuster? but I can't see any oil ways on mine so I'm not sure that's how it works on the R170?. when you take it off, the end of the shaft has a spring loaded free rotating bush which the spring holds in, so I'm guessing that the Mag Adjuster pulls that outwards away from the engine to adjust? But if anyone knows exactly how it works it would be helpful.
Many thanks for your help so far.
 

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Hi,

When you checked Fuel Pressure did you check it under load, (i.e. WOT pull in a high gear), if you are in any doubt at least change the Fuel Filter unless you have personally witnessed it being changed recently, getting charged for it by a garage does not always mean it was actually done.

After that, I'd very thoroughly check the continuity of the wiring from ECU to Throttle Flap Motor, also the actual connectors themselves, and if that is OK change that Flapper Motor.

That is a definitive Code you have their, act upon it before going off on a game of "Parts Darts" :wink:

It would also be useful to know what the Fuel Trims are doing, Lambda (O2) Data, and maybe check for Air Leaks, could have more than 1 issue here, but an Air Leak will throw the Fuel Trims to the Rich end of their limits ;)

HTH, Cheers Dave
 

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Discussion Starter #8
OK thanks for the info, gives me a few more things to check & I take the points raised on board. Would still like to know more about the operation of the Camshaft Mag adjuster for 230 R170 if anyone can give me precise info as I'm still leaning towards that as being an issue ( thinking there may be two separate problems)?
 

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Discussion Starter #10
Hi thanks for the info, but no not exactly, I'd already found that particular PDF online, and the adjuster on my car works slightly different (as per info in the start of this post). What I'm after is someone who has taken apart and understands the specific adjuster for my car (part No. 1110980009)?
 

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If you are running on straight unleaded try super unleaded mine will do a couple of tanks on unleaded ok the will cough and fart under heavy throttle, fill up with super, problem solved, so stick with super now, no more problems.

Regards Stuart
 

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Discussion Starter #12
Thanks, but have always run the car on a minimum of 97/98 Octane (99 if I can find it), found out very early on that it doesn't like 95?
 

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Replace your maf sensor. Ebay 48 aud $. Cleaning maf sensor does not mean you have fixed it. Had same issue and easy fix.
Try unplug your maf sensor and drive it for 5 min, and plug it back in.
 

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I simply do not understand the wish / advice to change a load of bits that are not showing an obvious fault code, when clearly the flapper motor or the wiring to it is :confused:
 

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Discussion Starter #15
Did try unplugging the MAF sensor but it ran very very rough & wouldn't idle, so not sure I could actually drive it like that drive like that?, agree the 0243 code is indicating the Air flap bypass as a fault, but have had info from multiple sources that suggests that this fault code can also be caused by issues with the Cam Mag adjuster or MAF sensor as the three work together?

Anyway I did replace the fuel filter yesterday as it's cheap and from looking at the old one had never been replaced, when I ran the car initially. it ran very rough as you would expect as it worked air out of the system, this improved with time, but as it got better the behaviour seemed very similar at around 2500rpm as they had been at 3200rpm (i.e. spluttering and dying until you backed off on the throttle?) this before it cleared up and resumed to where it had been before.

As previously mentioned I checked the fuel pressure which did seem OK, but this was only really a short static test, so I'm going to try testing it over a longer period to see if pressure drops of?

Just to say thanks again to all for your comments, I'm taking it all on board as it all helps be get my head around the issues I have with the car.
 

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Hi again,

Due to the nature of my business and the things that I see on a daily basis, I take almost everything I read with a pinch of salt.

I'm done trying to get my head round all this, so I just Skyped an old Nurburgring Buddy who certainly knows his Mercedes Benz Cars / Engines :wink: ........................

Straight from the "Horse (power man)" in Sindelfingen's mouth :-

P0243 .................

This fault is an Electrical Fault within the Boost Control Valve, or the Wiring from ECU to that Valve


Which just confirms what I already knew !!

Now, IMHO, if you had other Codes, yes they can stop that Boost Valve working, ECU will not switch it to Boost to prevent your Engine from melting, but as you only have Misfire Codes plus P0243 it is almost certain that the P0243 is the Daddy in this case and the others are just the Offspring !! Thing is if it were something else causing this it would not flag that particular code ;)

Now, there is one other possible scenario, the P0243 may be a Red Herring set by someone who believes in the dubious and pointless method of "unplugging stuff diagnosis", in which case it should not return once reset, so then we refer to the P0170 Fuel Trim Code, which could be blocked CAT or Air Leak, so those items would need testing.

Modern Engines would also put up an Air Flow Incongruence code in this case, but these old 4 Pot S/C Engines, I am not so sure ;)

One final edit .......

Did the "Launch" Garage reset the Codes, drive for a while and then see what comes back, that is good practice then you actually know what is a Red Herring and what is a genuine Code :wink:

Sincerely HTH, and look forward to the conclusive outcome :)

Cheers Dave
 

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Discussion Starter #17
Thanks Dave, that does give me more to think about, yes the garage that read the codes "DID" reset them so I agree would be worth getting them re-read?
Will let you know how I get on, may be a week or so before I can get back for a reading.
 

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Hi @Del Benson ,

Yep, deffo get them re read, ask garage if they can do a print out, also check live data on Fuel Trim & Lambda's while they are at it, if they can't print perhaps ask them to write down the readings this is all important :wink:

Launch is pretty good on major Modules like Engine so should get all we need without SDS ;)

Might be worth asking them to do a quick and dirty check for Air Leaks by dousing / spraying Carb Cleaner Aerosol all round Intake Manifold and Pipework, whilst the car is there ............ just in case ;)

I know fine well if you lived near me I could nail this well within 2 - 3 hours :wink:

BTW off topic, (but that's my middle name) lol ..........

What Engine is in your Kallista ?
When I was 19 I had a Panther Lima, lovely thing, it came with the 2.3 Vauxhall OHC but I bought it with a seized Engine and put a Rover V8 in it, Holley Carb, Cam and Extractors, proper weapon that was >:D

HTH, Cheers Dave
 

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Discussion Starter #19
Hi Dave, have had to shelve the SLK diagnostic for a while.....work got in the way, but will get back to it and let you know, in answer to your other question the Kallista has a 2.8 Cologne with a weber 38DGAS, have had the heads & inlet manifiold matched and flowed......goes pretty well, but always promised myself that if I blew the engine up at any point I'd try and get hold of 2.9i 24v Cosworth lump. (would drop straight in), then I could really scare myself :)
Cheers
Del
 

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Hi,

I have an almost complete 24V Cosworth Engine here, just head bolts and a couple plastic tensioner bit's missing), plus a load of new Gaskets and bitties, it will need a very light hone / wet and dry and rings / shells because it has stood with heads off in my shed for years, was a good running engine before I stripped it :wink:

I was going to short stroke it to 2.5 litre and run Twin Turbos in my Rally Car, but I never could drive it flat out with the 2.9 N/A Engine so never did it, gave up Rallying and sold the Car, a Ford Puma with serious shell mods and 4x4 Cosworth running gear :grin:

All built in house here ;)

You can have that Engine if you fancied a run up here in a small Van, I'd rather give it away to a forum member than scrap it, those Engines are a piece of history ;)


I sold the stage rally car to fund the SLK project, as I had to come away from the Rally scene years ago when we had 2 long family illnesses resulting in death of Mels Brother then her Dad, so rally car sat un used for 5 years :(

Anyhow, I've had more fun for a lot less money this summer driving the SLK than I did the few times I got to take the Puma down forest stages, so it was a good move, I can jump in the SLK any time and go for a blast, the rally car was no fun as a road car lol

Cheers Dave
 
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