DarthBudice

I rarely post - hello everybody!

I finally solved the off-the-line throttle lag on my '01 C240 M112 V6 and want to share my experience.

I was extremely aggravated (ever have that happen LOL?) to apply the
throttle from a dead stop only to have nothing happen for up to 5 seconds...
then REEEEEEE there she goes! This behavior didn't seem correct to me.

After performing the throttle reset procedure every 2 to 3 weeks for months
(yes, months), one day while I was out to lunch, I had to stop very quickly
to avoid being smashed by a cell phone driving a gigantic bus (some people
call them SUVs)... just to realize I didn't have power brakes like I did a
second ago! I could reproduce it again and again by braking hard twice.

I spent a whole weekend inspecting all the vacuum lines on the engine
and found nothing. After doing this again the next weekend, I realized
I wasn't seeing something... so I decided to inspect them with the engine
warmed up... and lo and behold, the partial crankcase breather hose
(I believe this is the term) was fsck'ing LOOSE at the cylinder head!!!
This is a short 4 or 5 inch rubber vacuum line that connects from the
back of the driver cylinder head to a red 90 degree plastic elbow that
rests within an inch or two of the air mass meter electrical harness.
Strangely enough, it seemed OK when cold, but when warm, it was
practically falling off.

One $0.10 hose clamp later and problem solved - haven't used the throttle
reset procedure in 3 months now and it's just as driveable off-the-line
in W as it is in S mode.

I hope I can help others by sharing this info, and don't get me started
on the rear SAM and power seat controllers LOL!

zoomie

Wow, thank you for that. Would this be applicable to '05 c230 Kompressor? How apparent was your lag at start off throttle? Mine has a lag, but i always figured it was designed that way. would you mind taking a photo of the area? i'm stupid when it comes to engines and have no idea what to look for to find that lose hose. Thank you!!

aznmode

I don't have that much lag on mine but just the typical one that a lot complain about. But I might try this to see if it helps. Do you happen to have an image of where this hose is located?

DarthBudice

I don't know much about the supercharged 4 cylinder - sorry.

I was getting 3 - 5 seconds of lag from the time I applied throttle
from a dead stop to the time the engine raced off to redline (with very
light throttle too!).

This is all I can get with my cell phone - you can see the red 90 degree
plastic elbow at the bottom of the picture. I placed a small hose clamp
at the other end - it's visible just to the left of the air mass meter
electrical harness.

If I didn't already know it was throttle-by-wire, I wouldn't guess it
by the way it drives now.

aznmode

Thanks for the pic. I have an M271 but it should be almost the same set up.

TruTaing

Glad it worked out for ya.

Ima go look at mine when I get a chance

M271 == I4 supercharged.. The MAF is in a very different place from the m112 (and maybe the m272).

edit: could someone w/ more technical know-how chime in on what exactly this thing is and what it does?

edit again: DarthBudice - did you have any other issues w/ CELs and what nots?

DarthBudice

No CEL or anything. I even spent $100 for an OBD-II cable to observe
real-time data (it's not information until you know what to do with it LOL!)
on ST and LT fuel trims, O2 sensors, and such. The part that tipped me
off to it being a vacuum problem was braking two times quickly I lost
the vacuum assist at the second iteration.

Hope this helps.

WaveyKat

ohh am about to try this on my C320... nice info...
but i do hate that 3-5 sec delay it SUCKS.. how did you get the clamp all the way down there... can you take more pix if you can please thank you!

GezaBMX

Hi everybody,

I know this is an older thread but I'm going to try my luck
I need to change my MAP sensor cause it's not working properly and also I noticed that the rubber lines are cracked here and there. Anybody have parts numbers for the rubber hoses for M112 2.6 V6 ? I can't find no info or maybe I'm just searching in the wrong place

Moviela

Head over to Pelican Parts. They have the OE hoses, and the prices are reasonable. I see your in Bulgaria, so shipping from California might not be so cheap. You can get the part numbers from Pelican and find them in your local market. Even if you go to the Mercedes dealer in Sofia, http://www.mercedes-benz.bg/ it will be less than the fuel you are wasting now.

GezaBMX

Hi Moviela, I already got the thin vacuum hose, now I'm just waiting for the MAP to arrive so I can install everything. I'm going to check out Pelican Parts for the part numbers. Mostly I order my parts from all over Europe cause It's a bit of a PIA ordering from the US because of the customs taxes and ... Will report back once I have everything and hopefully the sometimes difficult start will be a thing of the past

GezaBMX

So reporting back, I got the new MAP sensor, got a meter of vacuum hose and today I changed the MAP sensor and it's vacuum hose and also a few same size hoses in that region. After I assembled everything the car started first key like 5-6 times. I went for a drive and after everything got nice and warm the car yet again didn't want to start on the first key. At this point it's getting frustrating a bit but I have a suspicion that it might be related to other vacuum hoses or something minor. I'm open to everybody's suggestions in this matter.

samaritrey

Have you looked in to CPS. Very common to cause a no start when the engine is warm.

GezaBMX

Just today I learned this may cause the problem. The CPS is a commonly known issue for the m112. The only reason why I didn't do it before is because I had a clunky o2 sensor and the MAP (and didn't think of the CPS)
Today I found a vendor close to my place so I'll order it these days and hopefully will be able and have time to change it.

I'm also thinking of changing the fuel filter but if these two don't fix my problem then I really don't know what is wrong...
First I'll do the CPS then we'll see the rest

TTR

Man I wish there were more pictures for where this clamp thing is.

GezaBMX

In the next few days I'll order the CPS and I watched a few videos and pictures of other M112 engines so I'm confident I'll be able to change it. I just want me car to finally start first key so I can start with other things

GezaBMX

FYI that "watched a few videos and pictures of other M112 engines" sounds pretty ****ing stupid since I work on mine. Just wanted to put that out there

GezaBMX

Finaly got the damn CPS changed... it was a bit of PITA to change but got it done finally. Now it seems my car runs smoother then it used to before(used to run smooth but a difference can be felt)
After the CPS was installed and everything put back to place the car fired up no problem, went for a drive and it seemed like it's running a few extra horses(butt dyno). I left it cool for about 2 hours. When I went down it cranked a few times until it fired up. Stopped it and started it again and this time it was like instant.

Now my question would be what else can cause that delay when starting? What else should I check or do in order to get rid of this hesitant start ?

samaritrey

I didn't see if you had checked fuel pressure at the fuel rail yet or not? If not check it in a few different situations and see if it is low. (the spec has been posed on here many times if you search can't remember)
Also if fuel filter is old might as well replace it as it is cheap and hold the pressure regulator. (make sure to buy OEM/OES as aftermarket ones have been known to have bad regulators.

GezaBMX

No I have not checked the fuel pressure yet since I don't know yet how to but I'll have to research that. I was also thinking of changing the fuel filter since I don't know when or if it was changed. Guess this is the next step

samaritrey

To check fuel pressure you need to get a fuel pressure gauge (kind of like a tire pressure gauge) Then you go to the fuel rail and it has a port that looks like a tire valve and you check it with key on as well as can check to see if it leaks down fast or anything like that.
How many miles are on the car?

GezaBMX

I'm just about on 110k km, unfortunately I don't know if this has been messed with or not

GezaBMX

Is this valve you are referring to on the top of the engine, passenger side? Since there is a pipe right where the fuel rail and injectors are that has a small valve(similar to a tire valve looking) Somewhere I think I have read that this is for the AC? Are we talking about the same one?

pcy

The valve at the end of fuel rail is for checking fuel pressure. If you are not 100% sure which is fuel rail, I'd recommend you to take the car to independent mechanic.

The valves you are referring to are for checking pressure on AC lines.

GezaBMX

Regardless of the fact if I can "check" it or not, I will still take my car to the mechanic since I want to pull the codes. I don't have an ODB2 scanner so that is also on my purchase list of things. As far as I read, these cheap ones or cheaper ones are not the one I should buy. Is there a model that is better for Benz(other then STAR) and doesn't cost an arm and a leg?