Luke_Y

Hello, my sons 07 C230 sport (m272) is having some issues with starts when the temperature is cold, below freezing.

The car is relatively new to us, we got it this summer. On the first day the temp got into the 20s (f) we noticed it was a bad cold starter. It cranks for a long time and won't really start without the application of gas pedal. Even then when it starts it's rough, missing and stumbling for a few seconds as you apply some throttle to try and smooth it out. 5-10 seconds later it's fine and settles into a normal slightly high idle. Also seems to run quite rich when cold. Subsequent starts are fine.

If the temp is above freezing it seems to start fine, even if it has been sitting for days. So I would think it's not losing fuel pressure.

Usually he lets it warm up a few minutes before leaving when it's cold and he says it drives fine. Today (25f) he started it, it started ugly, but he then departed immediately. He said at the stop at the end of the block the RPM dropped all the way down and it died. Started again fine, and at the next block he stopped and the RPM dropped a bit but it didn't die. He drove around the block and home and it ran and idled fine. Don't know if this would be the usual cold start behavior but as he usually lets it warm up a few minutes. But, it has never died on him before.

No MIL, no codes..

Recent maintenance since purchase has been;

Oil/air filters/plugs
All fluids changed except transmission (on to do list)
Cam sensor magnets (p0012, 0022,0025 codes) -fixed
MAF (p0170,0172,0175) -appears fixed
Thermostat most recently- had poor heater performance, long time to warm up, temp gauge hunted, and one occurrence of p0128 -appears fixed

Have had an occasional p0420 pop up so probably will need cats soon, but with the above issues and maintenance the mil has been reset quite often over the last few months.


Car starts fine when the temp is warmer, say above freezing. Even if it has sat for days.. So any thoughts? Any help or suggestions would be appreciated. Thanks

Moviela

I would first examine the terminal voltage using the MFD volt meter just after cold start. Also check that the temp sensor that reads in the MFD is correct when below 55F. It shoots in more fuel to start earlier.

A low capacity battery or one that is tired will not have enough EMF when cold. The starter will turn slowly and the spark will be less "sparky." After starting the current from the alternator will warm the battery quite quickly, and spark will improve.

I would seriously consider a block heater if you encounter temperatures below freezing often. Oil turns into hair gel, and does not pump very well during starting. A plug in block heater is the way to go.

The last item could be dirty injectors or low fuel pressure. Easy enough to measure & fix the pressure, but cleaning injectors without a full off the car scrubbing and testing on an expensive flow machine is not productive. With the exception of Techron in the fuel tank, none of the potions really do anything beneficial.

Luke_Y

Moviela, thanks for the input and on Christmas Eve even.

I will check on the battery voltage. It appears to have the original battery.

I will check the MFD temp as well. To clarify; are you referring to the standard MFD displayed temp, or is there a reported coolant temp in the "dyno" screens of the MFD?

I'm of the mind that fuel pressure or dirty injectors would present a problem at all temperatures not just when cold. I could be wrong.

Lastly I can't believe that a car (any car let alone a mercedes) needs a block heater for operations in the 20s (f). I'm talking 27f not -27f. I see you're in CA but believe me 20s isn't that cold. 0w oil is quite viscous.

This car is completely normal @ 37f but ugly @ 27f...

Luke_Y

So a bit of probably not so helpful info: I went out to the garage and checked the temp display in the MFD against a thermometer and it was dead on @ 46f.

Checked the voltage in the MFD- 12.6 before start, briefly 10. something during start (so brief I couldn't catch the tenth), 12.6 for a few seconds after start then rising to 13.4 as RPM settled down, 14.3 as soon as I gave it some gas and stayed there.

Of course car started fine as it's 46f in the garage should have left it outside where it's 19f...

Is this temp reported in the MFD sourced from the HVAC system, or somewhere else? I would think for engine operating/starting parameters it would use the coolant temp sensor? Is the coolant temp reported anywhere in the "dyno" pages?

funnyent

If you're on the original battery, I'd recommend replacing it. My car had the same cold start issues and replacing the battery fixed it. When it gets cold the battery doesn't spin the starter motor quickly enough and it runs bad for a few seconds until the engine rpms get up.

My car has never died after starting, though, so there could be more to the issue.

Tim

Moviela

The terminal voltage dropping to ten is a bit troubling at 46F because it will be exponentially down at 20F. My feeling is minimum 11 volts down to about 50F, or find out why. While the nervous pile of chemical energy is the usual culprit, but it is not always the battery proper. It can be a cable problem, or starter problem.

The temperature sensor for the MFD display is up front to measure ambient air. The injection time is substantially increased while the starter motor is cranking if the temperature is below 55F. A slow starter running longer could cause excess fuel to be dumped into the cylinders. When detected by the HEGO sensor it could over lean the engine right after start causing the stumble.

After stumbling for a few seconds and then smoothing out could be gunk in the injectors causing the valve shaft to stick when below freezing, then after a few thousand operations the gunk around the shaft warms and becomes more lubricious.

The coolant temperature, intake air temperature, and HEGO voltage is available through OBDII.

Luke_Y

Hello all, a new MB battery appears to have done the trick. Started quickly @ 29f without touching the gas pedal.

Thanks Moviela and funnyent (Tim). I thought the voltage drop to 10 something during start was worriesome as well, but what tipped me over the edge was my son told me it started crappy the other day in the 40s. I checked it the next day in the high 30s when it previously would have been fine and it was rough, voltage actually hit 9.8 or 9.9. So, new battery it was.

Compared Duralast platinum (JC?) @ 95Ah, 3 year warranty, and a higher CCA rating to MB @ 100Ah, 2 year warranty and a lower CCA, both the same price @ $165. Decided to go with the MB battery as others report good longevity. Picked up the battery at the dealer proudly displaying a "Made in Mexico" sticker assuming its a Varta (JC). In hindsight the Duralast was probably the better deal. They are likely made in the same plant but the Benz branded battery is probably made to a 10 year old contract spec and the non branded battery may have been updated a bit along the way. Oh well done now and hopefully not to be worried about again for years.

Thanks again.

Luke_Y

Well I started his car this morning @23f; I had to give it a little gas to get it started and not running rough. Just for a second or two but still... It actually started quickly but kind of hangs just on the edge of being started if I hadn't gave it a little gas it would have bumbled along missing slightly and almost stalling.

Anyone else's w203 do that? Three other cars in our household all start without touching the gas when cold. They may crank longer and slower but they all start.

Luke_Y

So this is definitely still a problem. My son says that this AM @ 10-15f after it "started" it took 20 seconds or so of gas pedal application for it to stop stumbling and come to a normal idle. He said that while trying to get it to idle and not die it felt like the gas pedal was not really giving it any additional RPM, wether partial or to the floor. Then settled down and was fine/normal..

Also said there was a large amount of exhaust and it reeked of fuel, seemed like it was running extremely rich. I had noticed that once before on one of the first bad cold starts, large amount of darkish exhaust and terrible raw fuel smell. So bad i could even smell it at the engine compartment. Then after a couple minutes, normal..

Next thing I was planning to do was hook up to the reader and see what the coolant temp sensor is reporting on a cold morning. Maybe check fuel pressure at the rail as well when cold and during start.

Any thoughts/ideas on additional troubleshooting?

Thanks

VVF

Could it be a sticking throttle body restricting the airflow? Then when the engine heats up the TB 'unsticks'.

Luke_Y

Grrr the TB is a bit of a ***** to get to on the 272 c230. I don't know if that's it as it usually gets back to normal (within a few seconds) before it has a real chance to heat up any. But, I will look at it if the next checks come up OK.

I'll test fuel pressure and coolant temp sender reading in the AM. Anyone have the cranking, running, and leak down fuel pressure specs for an 07 m272 c230?

Luke_Y

OK some more info;

Temp this AM 43f, car started fine/normal

Fuel pressure-
Was zero when first hooked up (had bled down overnight)
Key on, immediately jumped to 58psi for the second or two that the pump primes, then settled at 55.
Start cranking 58, started and idling 56 and steady. Would only fluctuate a pound or two up or down when revving engine. Brief snap to wide open throttle would rise to 58ish.
On shut down it dropped to 53 and held steady there for 5 minutes, came back after another 25 minutes and it had bled down to 46. (may have even been my gauge as I could detect a slight fuel odor at the hose/gauge joint)

That all appears reasonable to me. Anyone see anything to be concerned about there?

Coolant temp sensor-
Well, this check was a bit compromised. I had started the engine and let it run for a few minutes about an hour earlier while doing the fuel pressure testing. I would have liked to check it cold at first start to see if it was at ambient temp and reporting correctly.

But, when I started it was a reasonable 25c and I watched it until the the dash gauge came alive @ just over 40c.

I need to repeat this when it's actually cold out and the car hasn't been started so I can see that it reports correctly when I know the temp should be about ambient.

My son has driven a couple hundred miles in the last few days and said that last night while driving on the highway the check engine light came on. Light was on this AM, the codes were P0420 & P0175 stored and the same codes pending.

The P0420 has been a reoccurring theme and I know I will have to deal with the cat soon. The P0175 is a bit of a puzzler. We replaced the MAF a few weeks ago due to frequently reoccurring p0170,172,175 codes. 170,172 haven't returned but this marks the second occurrence of the p0175 after the MAF change. Both times with a 0420 as well. Seems odd to me to have a 175 by itself. May well be completely unrelated to the cold start issue..

Luke_Y

Checked the coolant temp sensor on a cold start this AM with dash command. It was within 5 or so degrees of ambient temp (reporting -7c when ambient was -12c). Car started crappy, stumbling on the edge of starting, started and smoothed out within a few seconds of my modulating the pedal. It likely wouldn't have started without some pedal input. Slight whiff of fuel, but not terrible.

So;
Battery- check
Fuel Press- check
Temp Sens- check

VVFs suggestion of throttle body cleaning will have to wait until after my vacation.

I'm at a bit of a loss here...

WilkesG

I don't really know of a solution to your problem, although I noticed today when I started it in the cold, around 30 degrees, that it seemed sluggish at first.

I just bought this car a couple of weeks ago. I saw in your initial post that you've done a lot of maintenance since purchasing. Did you know about these issues when purchasing, or have you gotten this many error codes pop up since you've had it?

I admit to being a novice when it comes to Mercedes. I just bought it after driving a Lexus for 14 years and 174,000 miles with zero problems, but thought I'd get something a bit newer with fewer miles on it before the Lexus started having issues. Now I am reading about quite a few issues on this car, and I am far from a mechanic, I'm wondering if I bit off more than I can chew with this one.

Sorry to get off subject here.

Luke_Y

WilkesG,

It has hit us with quite a few of the most common problems in the first few months. This cold start problem apparently not so common.. As a guy who doesn't mind to DIY most things none of it has been expensive or difficult. The cat(s?) will be more expensive than I would like, and the cheaper option (universals) can be a recipe for problems. It is late 07 production and the serial # is out of range for balance shaft ($$$$) issues, so there is a large bullet dodged. On top of that we performed a good bit of scheduled/preventative maintenance right away as we have limited service history info on this car.

So, if we manage to dodge the transmission conductor plate issue I hope we are about to "get over the hump" of common >100k mi issues and he can have some years of relatively trouble free driving.

I don't know what your mileage is. If it's a good bit under 100k these sort of things may come more slowly for you, not all at once. Or, some of these common things may have already been attended to on your car.

To directly answer your question; no it will not be as reliable nor age as gracefully as a lexus/toyota or acura/honda. I would not shy away from DIY as many of these things are fairly simple and the forum is a great resource. There are several members here who know these cars inside out. I would get recommendations on a good independent mercedes mechanic/shop in your area for the things you don't want to tackle. If your serial# is in range for the balance shaft problems (search forum) I would have to give keeping it some hard consideration or at least know the early symptoms and trade it at first sign.

Luke_Y

OK so continued troubles but some additional things to consider.

This AM start @ -1f. Needed pedal modulation to start and run, huge plume of smoky exhaust that reeked of fuel. Spit out a puddle of oily fuel from the exhaust when it first started (never done that before - pic below). Ran like this for a few minutes and then started clearing up, eventually to seemingly normal. No check engine lights. (Edit-after 20 or so miles of driving it popped a P0420 again probably due to meeting readiness condition after being reset the other day) Subsequent starts for the day- fine.

I logged a bit of data with dash command yesterday when I checked the temp sensor. While reviewing it last night I noticed that the long term fuel trim for both banks was like -23 & -26…



Video (click on)


Video (click on)


This crap only happens when its cold out. I don't know.. It might be time for this to go to the dealer. If anybody has additional ideas feel free to post them. I will be out of touch for a week or so and may just have him drive my car. I'll check in when I get back and if nothing new Ill probably just take it to the dealer. If the weather's cold enough for them to reproduce the problem…

Thanks

WilkesG

Thanks for your the reply. This car DID have the balance shaft issue and it was replaced. I am at 97,000 miles right now. I am definitely going to use the forums and try to DIY as much as possible. I just had a rear brake lamp message come on today and already had a message come on about the turn signal on the driver side rearview mirror. The manual says DO NOT try to replace the LED turn signals yourself and to take it to dealer, but that seems a little ridiculous.

Luke_Y

Good thing that is already addressed, it's an expensive fix. With the mirror signal messages, check that it is actually out. Seems the mirror lights are sensitive to brief activation/canceling. My son got those messages for the first couple of days until he got used to how the signals reacted compared to his acura. Hasn't gotten them since.

Luke_Y

So, still having troubles with it and after the particularly bad incident above had pretty much settled on one or more injectors leaking/sticking when significantly cold and pissing fuel for just a bit after starting until they warm up a bit. Was convinced enough to go ahead and purchase a low mileage rail/injectors that a wrecker had listed for a good price.

My reasoning; There shouldn't be a default coded fuel map that would result in running rich to the extent that raw unburned fuel makes it out the exhaust. Only a few things could actualy make it run rich to the extent that raw unburned fuel makes it out the exhaust and only when cold out.

1) Leaky/sticky injector(s)
2) Runaway unregulated high fuel pressure (I think less likely to be a cold only problem- and when I checked it was right where it should be- albeit the temp was a 43f which doesn't present problems)
3) A dead cylinder(s) not firing and just pushing out the fuel (I would expect misfire codes and am not getting any)
4) An ECU that has lost its mind with regard to fuel mixture (Highly unlikely I would think and, it's trying to corect the problem hence the high NEG LTFT numbers)

Now, what gives me a bit of doubt. Last night after a particularly bad first cold (10f) start of the day I had him pull it in the garage before it cleared up and leave it until I got home. I wanted to pull the plugs and see if I observed one or a few to be fuel fouled. Well, they were all fairly evenly slightly fouled wet with fuel. I would have expected one or two to be fuel fouled and the others showing normal or possibly indicating a lean condition...

So now, I'm not so sure. I'll still proceed with the injectors when they come in, but I'm all ears if Moviela, Glyn, or any others have some additional input.

Thanks

Luke_Y

It was nagging at me that when I checked the fuel pressure it was 43f, a temp that the car starts/runs normally.

I checked it this afternoon @28f, a temp cold enough to give the long crank rough fuel smelling crappy start, but not cold enough to have a huge plume of exhaust and drip raw unburned fuel from the tailpipe.

Key on- 57 psi
Cranking- 55
Running- 55-58
Off- 52
5 min- 49
10 min- 48
15 min- 47
30 min- 45
50 min- 40
So OK I think...

It should be noted that the worst case huge exhaust plume/fuel from the tailpipe has only happened on 2-3 occasions. All when it was single digits (f). Even in those occasions it cleared up and ran normal within a few minutes (I'm assuming when it gets to fully closed loop). On subsequent starts even if it's cold out and has sat for several hours it's fine and normal.

TTR

Ya my 01 C240 can still start in -40 without plugging in the block heater. The car definitely feels frozen and was very slow to response, but still started.

Glyn M Ruck

Good cold starting on a gasoline engine needs:

Good winter gas with more light ends
Ignition system up to snuff including plugs
Fuel System up to snuff ~ fuel pressure >3.8 bar or 55 psi while cranking ~ Run some Techron Concentrate to make sure injectors are clean
Obviously compression
No restrictions air cleaner/inlet system or exhaust
And proper open loop mixture enrichment. This is dependent on the engine temperature sensor giving accurate information to the ECU on temperature.

Do you ever get a code 125/126?
P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control
P0126 Insufficient Coolant Temperature for Stable Operation

This is not a MAF issue. The MAF is out of circuit for open loop cold start.
You are over rich & thus getting rich fuel trim codes.

P0420 Catalyst System Efficiency Below Threshold (Bank 1) ~ this might be coming up purely because you are so over rich that the Cats can't keep up.

Some thoughts:

The car should start perfectly without having to touch the throttle
The throttle body might be having trouble holding the throttle plate at high idle. Make sure it is clean
You have replaced the electronic thermostat ~ tick ~ good
Are your air cleaners spotless?
We might have a clogged Cat/s
Does the excess air pump start & run normally
Is the EGR circuit & valve clean?
At minus 12 deg celcius you need decent winter fuel & everything up to snuff for easy start. A block heater will help but minus 12 at the same time is not that cold but certainly in the trouble range.

If this were my car & I had checked everything properly I would fit a new engine temperature sensor. I hate throwing parts at cars but if you don't want the dealer diagnosis expense this is a good place to start. It will either cure the problem completely or make no difference at all. Then we have that variable off the list.

It seems that the ECU is creating an over rich start environment. This could be due to bad temperature information. Frequently the case with Bosch systems. The other problem could be insufficient air due to items listed above.

Good luck!

PeteyV

I've had this same issue with my 2004 C230 since the first 2 weeks I've had it (first owner purchased June 2004). Car stumbles at starting in cold temperature and it has died on me 2 times in the last 10 years when starting cold. I've had to do the same exact things you and your son have done (applying gas pedal slightly to keep car from rumbling). I've taken my car to the dealer multiple times for this issue. They replaced my spark plugs 2 weeks after the car was delivered and the problem went away for a few months. Then it came back and I had my cylinder head replaced because of carbon build up. Car ran well for a few months then it reoccured. Now that I have been out of warranty for 6 years I do not take it to get diagnosed at the dealer or to any mechanic I just learned to deal with it. Oh I also change all my filters on time and have replaced my thermostat. My car is in pretty immaculate condition and service is done regularly so it is not like I ignore it. Sorry this isn't a solution but I just wanted to let you know you are not alone.

Luke_Y

Glyn- I went out today (28f) and had my son start it to check if the air injection pump was running. I don't think it was. I thought it would throw a code for the pump not running as it's an emissions thing.

It started in its usual cold manner with long cranking, bumbling on the edge of being started, finally "starting" but needing some throttle manipulation to smooth out, and having fuel stinky exhaust.

I had the air box off (so,not air filters they were changed a couple months ago anyway) and had one hand on the air pump, one hand near the end of the pump intake hose, and my ear near the pump. I couldn't detect that it was running. Didn't notice it by feel or ear and didn't note suction at the hose end.

Is there an appropriate relay in the box that I could swap with to see if it makes a difference?

I was going to move on to swapping out the coolant temp sensor as I have one and cleaning the TB. But, guess I need to make sure the air pump is working first.

Luke_Y

Glyn, sorry the rest of your questions.

Never had a code 125/126
Air filters standard and only a couple months old
Didn't think the 272 had an EGR valve?
Last 2 tanks ran Techron