hi guys,

my 2000 S430 (113,000km) has been having acceleration problem for a while. i just replaced the accelerator pedal module and while it has improved the response, the problem has not gone away.the car is not responsive under full acceleration.it starts and drives well for the first few minutes.it accelerates smoothly under normal driving condition but all i have to do is to give it a full throttle/kick down.

it holds back and tries to rev up but without acceleration.it eventually catches up, kicks into right gear and speeds up but with several seconds pause and feels like it is going to stall. if i repeat this it keeps getting worse and sicker every time.at this stage if i put the car in neutral and even press the pedal gently i can hear and feel the engine coughing and revving up very roughly and it is shaking.

if i turn the engine off and on again it seems to be fine for a while until next time i push the car hard. occasionally i can smell like half-burnt fuel/rubber/sulfur after i have stopped and shut off the engine. the gears change up and down fine and as i said in a normal city driving condition if i'm gentle with the gas and not going uphill or doing open road speeds most likely i wouldn't notice it. i remember when i took the car to my mechanic a few months ago he said there's a P0170 misfire code. he cleared the code but did not do anything else.

i have been having this problem on and off for almost 3 years now. it was once every six months for only few seconds so it didn't bother me much before. but it's been getting worse over the past several months. i've been reading the forum about similar problems. some relates to pedal module, some MAF and there was one transmission related. the car has not had any filters replaced for at least past fours years (40,000km). can it be MAF or there is more sinister problems?

i am really missing the sound and acceleration feeling of my car but now even passing other smaller cars on motorway is a painfully slow task and taking off at traffic light is completely out of question

 

If you use petrol of insufficient quality then you will get knocking in the cylinders, as the fuel ignites too early. Your car has a knock-detection system and slows down the engine to prevent early combustion.

Try to put top grade premium petrol into your car, higher than what the car needs. In Europe that car needs 95 octanes. Try 98 octane fuel to rule out knocking.

 

thanks for the reply.trying to to some save money i've been putting 91 into my car recently guess that's been causing more problems! is 98 octane a recommended grade for our cars?
i had P0170 and P0173 codes and apparently they are fuel trim codes.do i need to clean or replace any parts to fix this loss of power problem?cheers

 

If the problem is now constant and easily witnessed by the mechanics, take it into a qualified shop or a dealer for diagnosis.

Intermittent problems are the hardest to fix, but if its happening all the time a qualified MB tech should be able to solve it

 

It could be a one or more number of issues?

Clogged cats.
Bad Coils or Bad Plugs (since you referred to the misfire)
Clogged up fuel filter - With today's crummy gas, I've seen fuel filters bet pretty nasty within 5,000 miles.
Bad transmission.
etc
etc.

Take it to a shop, spend the money the car asks for and fix her up. You'll be happier in the long run.

 

If you ran on 91 Octanes (European Scale - no NA!!) then your car would exhibit those symptoms. You need 95 Octanes. The best is to drain the petrol tank with a hose pipe.

If you cannot do it, immediately fill it up with the best petrol you can find (at least 98 octanes, ideally 100 or over) as this will then create a mixture of about 95%. If the tank is still full you need to do that twice:

Fill it up with 98+ Octanes, drive until 3/4 full and then re-fill again with 98+ Octanes

 

In my experience, if its a clogged cat, when you give it a lot of throttle, you generally hear a hissing noise as the exhaust gases try to exit the cat from any opening/joint along the way. Pressures do build. Do you hear any hissing along the whole exhaust system as even the mufflers/resonators can plug.

To me it sounds like the MAS (or potentially 02 sensors) are going/gone or if you have multiple coils (1) of them may be going bad, most probably the MAS though. If I remember correctly, the errors you are getting are the trim errors and mean that stoic (sp?) combustion is not occurring. To much fuel will cause the value to go rich. I had a similar situation with a W140 where (1) of the (2) coils kicked out causing raw fuel and air to flow into the cat. The cat tried to burn them on entry, resulting in quite a stink of sulfide around the car. Funny thing is the car ran real smooth on only (4) of the (8) cylinders, just really lacked power.

I personally don't think its your octane fuel supply as the systems are smart enough to retard the system to prevent knocking, and then MAS/O2 system will adjust the air/fuel mixture to get stoic. You may loose power, but you shouldn't be smelling anything but regular exhaust.

My opinion anyways.

 

been using 95 and no difference noticed. I'll fill up with 98 tonight and see if there's any improvement. the smell is worse after a hard drive and it's coming from the exhaust because it's stronger at the rear or when i reverse into the garage.

now that you mentioned I do hear a low hissing sound like a valve opening or air escaping when i floor the pedal. to me from behind the wheel it feels like something's clogged or blocking the air/fuel flow. it fails to respond when there is high demand and it manages fine when not pushed hard.

previously this problem was intermediate so very difficult to explain to dealership or my mechanic. I've spent a lot of money trying to diagnose this over the past several years. it's just recently started to give trouble all the time so probably good time to take her in again and have her checked by Mercedes service centre here.

thank you guys for all the info

 

turned out the problem was 'Air Mass Sensor'! we replaced it and the car is a beast again it cost about $NZ700 including labor for a genuine Bosch sensor ($NZ549). not sure how easy the job was or how much i would've saved if i'd done it myself?

thanks a lot guys for all the information. love this forum, i gain so much experience and knowledge from here.

 

Like I said...."Air Mass Sensor" to me is a "Mass Air Sensor", MAS......

Glad you got it fixed though!

You paid about $NZ150 to open the hood, remove the air cleaner housing, unplug the old one and reinstall. They are usually not that difficult to get at and install, but, I am not familiar with your car. I'll bet most of the cost was to plug it into the diagnostic machine and I certainly wouldn't want to just randomly buy a new one and plug it in on chance that it was the culprit. So all and all, not too bad a nick.

 

i have a similar problem but i have a s350 cdi blueeficency
anybody else can give me some information
much apreciated

 

Do you have W220 S350 CDI...??

ZAYED,,

 

Yes i have a S 350 cdi bluefficency lwb.
2010.

 

S350 2010, means you have W221 not W220, have to post in W221 section,

BTW; did you try to diagnose your car..??

ZAYED,,

 

No I did not.

 

Your car doesn't have MAF sensor, it has pressure sensor(see attached), you may have an issue with this sensor, or other things, can't assure that..!,

importantly to diagnose the car, before spending $$$$, codes will tell everything easily...



ZAYED,,

 

Thanks Zayed
I will diagnose and I will get back

 

Any Time...

ZAYED,,

 

Hope this is still active. Over the last few days I been experiencing an issue that is similar. I put the car in Drive and it does not automatically roll like it used to. When I press the gas it moves a bit but feels like something is holding it back to keep it from driving. It almost feels like when you used to forget your emergency break on and try to pull off. It moves but it keeps getting pulled back. This happens in drive and in reverse. When driving, I see the rpms shoot up. it does switch gears and then rev's up. Any ideas? 2015 S550 about 35,000 Miles

 

This is a W220 forum - the newest W220 is 2005. Many, many changes between 2005 and 2015, so our knowledge isn't worth much for you. Sorry...