jp196400

so I have noticed my car shaking at idle, and even gave me a bit of hesitation when I accelerated the other day.

it seems to be getting worse, I have cleaned the maf sensor and it didn't help, I have also checked for leaks where the maf sits and found nothing.

I know ultimately I will probably have to bring it to the dealer to get checked but in the mean time I'm just wondering if anyone can point me in the right direction for anything else to check?

I have access to a snap-on scanner but I'm not sure if that will even show anything (no check engine light) do these cars need a special scanner?

I'm hoping it might be an easy fix like a coil or something but I'm new to Mercedes and don't have a clue.

any help is greatly appreciated.

ohh I have searched and didn't find any really hard answers.

Rudeney

How many miles on the clock? If it's over 100K, it could be cats, but it could be other things - fuel pump, fuel filter, MAF, bad gas, etc. I'd go ahead and pull codes. any OBDII scanner will work for the engines codes. You do need a specialized scanner for other systems - transmission, SRS, etc. Even if the MIL is not illuminated, there could be stored codes.

jp196400

It just turned 70,000 km, I'll go ahead and pull the codes and see what I find.
I just bought the car a few weeks ago, not sure if I should bring it back to the dealer I got it from. It's not an MB dealer so they'll probably tell me to stuff it. Lol

mis3

For me, I used to have idle vibrations and I did a ATF pan flush then they went away.

Unless you have the service histroy, I would go ahead to do the ATF change and oil change first.

jp196400

wow really? I thinks its due for the atf drain and fill anyways.

I just checked and it shakes it all the gears including neutral and park. not sure it that would make a difference to anything or not.

mis3

I used to have vibrations at all gears but it was more obvious when the car was at PARK. The vibrations would lessen when the car was at NEUTRAL.

Even if this does not resolve your issues, your car will definitely drive better. I went to an indie for this job but there is a few DIY somewhere in this forum. Please make sure you use the 236.14 fluid.

jp196400

great thanks for the info.

I was driving today and it almost stalled on me then got better for a while so it kinda goes n and off.

Glyn M Ruck

Read those codes. If it's a Snap-on Solus it will read everything.

70,000 Km's is low so unlikely O2 sensors which can cause stumble. It could be something as simple as plugs if the car has been an in-town queen where it does not run in the self cleaning range often enough.

jp196400

a friend has a snap on, I just have a crappy code reader.

might not be a bad idea to pull a few plugs?

on another note I have just noticed I have the Valeo rad so I guess it would be a good time to change that and do a drain and fill on the transmission.

is there and special way to fill the trans?

jp196400

ok so I scanned it with my code reader and nothing came up, I also pulled 2 plugs and they seem to look ok but I'm no expert.

sorry for the crappy iPhone pix

TheXenochrist

My car does the same thing, when in DRIVE and stopped at a light, the car rumbles and shakes. I just hit 90,000 km. Hopefully get the transmission flushed next week, and hopefully cures the problem.

mis3

If the RPM fluctuates, it may be the MAF. I had to replace mine at 110k km back in May-2008 under warranty.

My experience at the time was when I stepped on the gas at the light, the RPM would fluctuate. It felt like that the engine would die on me.

TheXenochrist

They RPM's do drop to about 500 when in drive. In neutral they jump up to around 700 and the car feels fine. Another w203 owner I know said he had the same problem and got his transmission flushed and it went away.
How much would replacing the MAF cost?

mis3

At the dealership, they charged $450 CAN for the MAF, then 0.7 hr for Electrical System Check and 0.6 hr to replace the MAF.

Glyn M Ruck

Plugs don't look too bad & you would have misfire codes stored if it was plugs i.e. P0300, P0301 > P0308 etc.

Service the transmission & take the car for a good Italian tune up. Good hard drive on the open road. Could be a MAF or throttle body issue.

Run a couple of tanks of gas with Techron concentrate in case you have a fouled injector. For best results use Techron in a lot of stop/start town driving. It is most effective with frequent soak periods.

jp196400

I plan on doing the trans service in the next week when I do the rad.
All she gets it the Italian tune up lol I drive it very hard.

I did remove the maf and clean it, I would think if it was the maf then I would see some sort of difference either better or worse, but I don't have much experience with maf so that thinking might be way off.

is there a way to test the maf? or test the coils, just to rule that out?

mis3

This is new to me. I did not know that Techron works best in stop and go traffic. Do you know why?

What I do is to make sure it is added to an empty tank and go an oil change afterward.

Rudeney

You could use SDS or another scanner to read live codes and you might find someone who can really interpret the data and tell you if it's the MAF, but honestly, I'd just go ahead and clean the MAF first.

Glyn M Ruck

The MAF is a difficult component to test as is the throttle body. Both don't throw codes - only related codes e.g. "lean on bank 1" etc. One thing you can do to check the MAF is to unplug it which forces the ECU onto a default map. If running cleans up you know it's the MAF. Some ECU's don't like this & the car runs roughly - others not & no one including my service manager can explain it to me. On the M112 engine it was always a good check.

Coils - If you had coil trouble you would be storing misfire codes.

Throttle body. Some throttle body actuators develop a flutter in their operation which throws no codes & the only fix is replacement. This is expensive & a dealer has the pleasure of trial & error with new parts that can be returned to stock which leaves us DIY'ers in a bit of quandary.

Please also check fuel pressure at the Schrader valve in the fuel rail that connects to the injectors. s/b >55psi/3.8 bar.

Glyn M Ruck

Due to my previous employer I know Techron well . I am impartial on this forum so I tend to keep quiet about my specific past.

Techron removes deposits more quickly in conditions of warm up, shut down & heat soak. So these stop/start cycles help the detergent remove the deposit/s quickly.

It still cleans just fine at constant open road RPM - It just takes longer. That is the nature of the additive without giving away proprietary information.

jp196400

that's a great idea although I would have to find someone who knows what there doing.
I already cleaned the MAF

Thanks so much for all the help guys.

so I will unplug the MAF and see if it helps, its **** pouring rain here today so it's probably going to have to wait till tomorrow, and at least I can have some comfort in knowing if it was a coil it would throw a code.

as for the fuel pressure, do I have to run the car or just turn the key to the on position. I've never checked fuel pressure before.

jp196400

what about a vacuum leak, could it be that as well?

Glyn M Ruck

A vacuum leak can certainly cause this problem. Vacuum leaks if bad will sometimes throw a "lean" fuel trim code. Aircleaner not properly fitted to the MAF will also cause bad idle & is very common but you have checked that.

Fuel pressure should be checked while cranking.

jp196400

yeah I have checked the air cleaner. still haven't had time to check the maf or fuel pressure, the weathers been really bad lately. as soon as I get a nice day I'll let you all know what I find.

sleepyheadzzz

this used to happen to me all the time...i thought it was triggered by my K&Ns so i changed back to regular filters...but then it came back about 3 weeks after....i took it in to the dealer and they even felt the hesitation...they reset the codes...whatever the hell that means...and it diminished by about 50% then 2 weeks later, it came back and i brought it in to the dealer...then they said "oh thats normal for the V8s, theres nothing we can do about it" but since ive installed my quad exhaust and sprint booster....the hesitation has completely disappeared...i'm not sure what happened.... buts its a pain in the butt when you buy an expensive car and it hesitates like a ford pinto...and the dealership calls it NORMAL