4 Fouled Plugs on 96 230 SLK - Advice Plz

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sandyhen

New Member
Joined
Jun 4, 2007
Messages
28
Location
Sunny Wigan
Car
SLK 230K
Hiya,
Sooo fed up with the Merc these days, any advice on the problem below would be great thanks.
The car has been running rough recently, with my Mrs saying that its loosing power. In the past I have replaced the mass airflow sensor twice over a couple of years, seemed ok to me, but I drive the Merc nice & steady, my Mrs floors it (says she does'nt)
Today:
Just pulled & inspected all 4 plugs - All Very sooty.
These are my thoughts:
Can't be a coil pack as all 4 are sooty not just 2.
I think I need to replace the MAS yet again (why would this keep failing?)
Or, am I replacing the wrong part & should maybe try replacing the lambda sensor instead?
Cant tell you how much im fed up lol.
Should I just take it to an expensive garage & plug it in to the fault code reader?
Thanks, Chris & Sandy.
 
Are there any warning lights up on the dash?

What's the fuel consumption like?

If it's running that rich for the plugs to keep sooting up I'd have thought it would stink of petrol and use a lot of fuel!

As it seems to be a constant fault and you've already spent money out on replacing the MAS twice it's surely got to be worthwhile taking it to a MB specialist to have the fault diagnosed properly :)

Best of luck,

Will
 
Hiya Will,
We can't beleive your still here! lol
You helped us out half way through 2007, many thanks.
Re: Today,
Nope, no stink of petrol.
It starts fine, then within 10 secs, runs rough.
Did forget to say that before the rough prob, engine fan constantly runs 20-30 secs after start up, even though car is normal temp range.
Got the plugs soaking at mo, cleaning them & trying to make it to garage in the morning, but would hardly drive up the road earlier on.
Will post again after garage. (they owe me for replacing one of their office windows FOC lol) Cheers.
 
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You are not too far away from Mr Walker at 124 works at Kirkham, Think I'd take a trip over there and get an expert opinion.
 
Hiya Flan,

Thanks but I dont think the car would make it!
I'll give a Merc Man a call, he says he uses a Star reader or something?
I bought an OBD2 reader with 32 to 16 pin? but sadly only works on 1999 onwards.
Cheers.
 
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Hi All,
Just cleaned & replaced plugs, blew out MAS with air hose.
Thought I could get car well enough to take to the garage, but no, still sounds like its running on two cylinders.
Barely ticks over, very rough.
 
Faulty cat or lambda sensor maybe?
 
How well does it run with the MAS unplugged?

Will
 
Update:
1) Tried running with Mas still connected fine for 30 secs, then very rough & revs dropped.
2) Unplugged MAS, exactly same.
Noted:
Each time I turn engine completely off & back on again, fine for first 20-30 secs.
Each time I turn engine on, main cooling fan slowly builds up to full speed & stays on full pelt.
Car is parked, engine is cold.
The mystery deepens?
Any guesses? Thinking towards lambda/ox sensor as stwaty says too?
Chris & Sandy.
 
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Ahhhhh...... just spoke to a different Merc speacialist (Jason, Ashton-in-Makerfield) sounds like a nice guy, told him the probs, says he has done a few just like this, all 90's cars and says that there are two holes that get blocked up under the inlet manifold that cause oil to be sucked through the intake system, this clogs up the MAS too.
He recommends removal of the inlet manifold, clean the holes, replace the hoses.
I'd better get scruffs on then! (cant wait to find these "holes")?
Will post update.
 
Sounds similar to the the Smart car which has a crank breather pipe with a one-way valve that can get stuck open. I replaced it on my wife's car for ~£10, though that car is turbocharged and not supercharged like yours.

some info if it's on any interest:
Evilution - Smart Car Encyclopaedia
 
Looks like you could be right Wemorgan, and yes it was a tenner from main dealers in Warrington. Thanks for your input.

2w5rabp.jpg
 
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After some good advice from Jason Bailey (J Benz Tech 07813 621969) I stripped out the inlet manifold, fuel rail etc, & had a go at cleaning out the breather nipples. The breather pipes just cracked off & looked well over due for replacement. Bought parts & one pie on back order, fitted a new air filter, ordered another MAS & will rebuild in the morning hopefully.
6nryg3.jpg


2v9sykk.jpg
 
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Hiya People
Update,
After waiting to pick up & re-fit new breather pipes valves etc, car exactly the same as before, however because it felt "lumpy" I thought to myself that surely one or two plugs can't be firing to sound like it does, so set about pulling off one HT connector at a time & re-staring the engine each time.
Result:
Plug 1 & 2 made things much worse, plug 3 and car sounded same as before, bingo! checked the rubber sleeve end bit where it joins to the top of the plug & it is severely corroded, so I think the spark must be tracking across to the rocker cover. Either that or a new coil pack, but No 4 plug is ok? wouldn't a duff pack effect both plugs? not just one?
I also think that because all the plugs were sooty before hand, I had no chance of distinguishing a good cylinder from a bad one at the first inspection. Lesson learned.
I'll buy a new coil pack end sleeve first & see if that fixes the problem.
Just goes to show how something simple can be easily overlooked.
 
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Leave both coil packs for now. Get new boots for all four plugs and leads made up as well. Get both from dealership, they are not expensive at all.
 

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