So with the exceptionally cold weather we've been having here in the UK, my SLK 230 has taken a turn for the worst...
Cold starting (definition of cold - 5C or below... but its been that every day for 6 weeks so if its JUST an ICY COLD start issue and not just a cool start issue I can't confirm yet) theres a large amount of white smoke (well, smells like fuel vapour) coming out of the exhaust while it warms up. Generally, it's only for the first... 1 minute lets say.
Fuel economy has gone right down (32MPG highway, UK MPG that is, which isn't AWFUL but considering 4 months ago I got 42MPG highway after it was serviced...!! It was averaging 38mpg before these problems certainly), not a huge drop in performance.
Anyway. Rounding it down and with some reading it seems to be the O2 sensor, I think. The engine sounds a lot louder and throatier, which to me assumes a richer burn (assuming that the only variable that could have changed is the fueling). But I just wanted to ask if there was anything else to check first?
I've had the problem of the oil seperator breather pipe leaking oil into the airbox, plus the fact I've got a K&N (think I'm going to clean it out on Tuesday, will avoid reoiling as much as poss) doesn't help. Cleaned out my MAS and the problem went away for about 2 days, but then came back. I'd daresay its a combination of MAS and O2, but I really don't fancy replacing both... just given I drive 500miles a week, the extra 6mpg would be £££ back in my pocket
If you use too much K&N filter oil, it can coat a thin wire, and cause rough running. I think the wire is in the MAS. You might just clean the MAS, and throw away the K&N.
wouldnt the ecu richen up the mixture to compensate for the extremely cold air being sucked intoi the engine?
just as an example i had a truck with a bad temp sensor. told the ecu it was -40 degrees on a 70 degree day. ecu was dumping fuel into the engine to compensate and truck would even idle.
just a thought
A little bit of white smoke is usually condensation burning off when cold however excessive white smoke is more serious like a head gasket. I would check your oil and coolant for mixing and also do a leakdown test to confirm. A rich running condition will not produce white smoke. When a head gasket is really bad, you may get a condition called hydrolock.
Damon
See now this is the thing I've had a blown head gasket on a previous car before so that was my initial guess, but that had smoke while driving not just on warm up. And the amount of smoke seems far too much to just be condensation. Then again IIRC there's a slight problem with my exhaust ATM with a dodgy downpipe-cat bolt, so perhaps when I switch engine off the exhaust is just letting an excessive amount of moisture in the exhaust as the damp cool air rushes in to equalise the hot exhaust, on the inside? And hence all this smoke on startup? Plus, I'm not loosing any coolant. I'd love to ditch then K&N for a Green, but quite £££ for a filter...
I tossed my K&N's years ago. Anyways, I think the prudent thng to do is to do a leakdown test. A bad headgasket could foul the O2 Sensor anyways. My wife has a 928 that blew a head gasket. It had white smoke for an extended period of time that would burn off. When it got real bad, it locked up the engine on start up(hydrolock). You can't compress water. Oh, never use tap water or this is what can happen:
I guess you can say it actually blew a block. My guess is that the previous owner used tap water from an unknown source that contained minerals that aided corrosion of the block.
going to pop it down to ATS in the morning, get it on the ramps and just rule out an exhaust related problem first (have had some niggles with exhaust on my car before), then will get on with this, cheers
I belive your problem is a "non problem". What i'm saying is that the smoke issue and bad fuel economy is quite normal during winter condotions. I'm currently driving my car in about -15 to -20 degrees celsius in Sweden and some white smoke from the exhaust is normal for any car in this climate.
Cold starts are VERY bad for the fuel ecenomy (and for the engine in general as well). Many people in Sweden use "engine heaters" to prevent excessive wear on the engine and to improve fuel economy.
It is true that coldstarts will decrease fuel economy somewhat. When the temp sensors are below a certain threshold, the car will start and run on open loop which means it will ignore the O2 sensor and enrich the fuel mixture until the car has warmed up. It might take longer for the car to warm up in your wintery conditions. Condensation burn off for about a minute probably is not outside of possibilities. It's a good sign that you are not loosing coolant. What does the oil and coolant look like?
checked the coolant - its still at the absolute maximum, with the last time I checked / topped it up being a good 2/3 months ago
so i think you might be right in that this may be a non problem! fuel economy has gone down from c.40mpg to 29mpg, just seems like a bit of a nosedive for just a spot of cold weather... but, now that its looking like its going to warm up I guess its just a case of wait and see if the problem resolves itself, and avoid too much driving in the meantime? I'm giving the air filter a clean atm (going to use the absolute bare minimum oil on it this time), and clean out the MAF while I'm at it... hmm...
oh, I have a technical drawing that I got from Mercedes of the air intake system (post intercooler), I'll scan it in and upload it in a bit - I'm sure it will be of some use to somebody on here
I have had K&N on my Porsche for over 10 years. The original instructions said to wait 50,000 miles to apply any oil. If you have oiled only once, you may have too much oil on it. Many guys on that forum complained that the oil had fowled that tiny wire. If I were you, I would go back to the original or somehow clean all the oil you can off the K&N.
i havent oiled it before it was just "new, as stock". mind you, as stock may have been overoiled. At any rate, I've given it a thorough cleaner (got a K&N recharge pack thats been sat in my cupboard for a year) and its waiting to dry atm. Going to go VERY light on the reoiling... I'm tempted not to oil it at all, to be honest. The mesh / foam should surely keep out most major particulates... though I guess the finer particles are going to do much good to my engine over time... anyone tried non-oiling before?
Jeez, don't do that !! - The damn things don't filter very well when oiled - without oil you'll ruin your engine -- air/grit filtration is the #1 protection for your engine by far (forget all the sexy oils - no comparison)
google for research and articles on oiled filters - not good and that's leaving out the MAF issue (there's also some discussion on our posts about this)
heh well it doesnt sound particularly much a good idea in theory but i was just curious whether anybody had tested particulate filtration for oiled against unoiled K&N filters guess its a no-go then... never mind i'll just play light with the oiling and give the MAF a spray down...
It seems unlikely that a new KN would be over-oiled. However, stranger things have happened. Does it feel or look oily? If not, you may be OK with that filter. Do your instructions still say to wait 50,000 miles before the first oiling? If you don’t have enough miles on it, just don’t oil it.
Since you have not oiled it yet, the KN may not be your problem at all. However, I would put the original filter back on, or get another non-oiled filter, clean the MAS again, see if the problem clears up. You may be able to get an inexpensive filter from your local parts store. Most of them have websites where you can get prices for your model. If the problem comes back, you can go back to the KN.
You can google about KN filter comparisons. A few years ago I read some studies. I don’t recall the results. It may depend on the studier. KN claims to add some horsepower, and to be effective in filtering. I wouldn’t doubt that. The oil problem is well known. A trusted Porsche 928 parts supplier will not sell KNs or brake dust shields because of well known problems.
I'm a bit skeptical of K&N's and oil filters causing issues... I've had mine (a POD type) for over 2 years and no issues.
More likely cause is a dodgy PCV valve/system. people with NO aftermarket filters still have issues with their MAF! I dont know why benz let the vapour go through the intercooler and MAF. It would make sense to plumb it in AFTER the MAF into the intake plenum?
below are pics from a E55 AMG internals approx 110,000kms note how much gunk has built up and a lot of it is due to the PCV. this user after doing his rebuild is using a oil catch can.
I vent mine straight and dont plumb it back into the intake... i run subaru upper engine cleaner/seafoam once a year to clean out any carbon build up if any..
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