S55 AMG will not accelerate (and it should!)

[slowstarter]

Hello!

I am new to the forum and am hoping for some help/advice. Yesterday whilst running my mother-in law back to Wales my S55 would not accelerate when I tried to pull past slower traffic on the M4 at a little above 70mph. This had happened before but not quite so severely. Previously I could take my foot off the accelerator and accelerate very carefully to get speed back up.

This time no matter what I did I could not get the car to increase speed. In fact it went slower and slower and luckily I was approaching the Membury services so I pulled off and sat at tick over which sounded incredibly rough and was very uneven for a few minutes while I looked out my RAC card. Before I phoned them I thought I'd just try turning the engine off and then starting it again.

Immediately I had the nice smooth tickover and the throttle response in neutral was instantaneous. I pressed on with my journey (I had a tee time booked with a bunch of mates so was reluctant to just abandon the day) and managed the rest of the journey accelerating and decelerating on the cruise control.

On my journey back I managed to rfeplicate the lack of throttle response by just switching in and out of cruise with a 30mph gap between actual speed and cruise setting. It just died until I switched off cruise and coaxed the car back up to speed on the throttle.

Had my game of golf and called the RAC to my mate's house. No good, their diagnostic kit will not work on Mercedes.

The RAC man guessed at maybe something to do with a build up of gases in the catalytic converter or possibly something to do with the turbo. (I don't think it has a turbo? As you can now see I am shamefully unaware of the technical specification and needs of my car.)

I am nervous of just handing the car (57000 miles and year 2000 registered) over to anyone without having a good idea of what may be wrong and an idea of the budget I am looking at to fix it, as times are hard and if I have to I will leave it until I have the cash to fix it properly! But if I am looking at something as simple as plugging in some diagnostics software and remapping the engine (if such a thing is/can be done on this car) then I'm up for having a go at that.

I appreciate it's a long winded post, but would be really grateful for any pointers. Plus any suggestions whether any of the hometune type organisations would be worth considering for a fix?

Thanks

Martin

 

[recycledjuvenile]

it certainly has not got a turbo. smells like the MAF to me or it could be that the cruise function is messin gup the settings
Either way, it would need the codes reading

 

[recycledjuvenile]

have you tried a star machine

 

[Xtractorfan]

I would certainly be thinking along the lines of the air flow meter, MAF, as stated, it might be worth unplugging it and trying the car, some systems will run perfectly well when they dont know the maf is missing..

 

[GCLTuning]

Yes this is correct .

unplug the MAF

then run the car ( 5 mins)

then go for a drive and see if there is a difference

This will revert the ECU to a default setting if there if no FLAT spot then you will know what the problem is !

Kind Regards GCL Tuning

 

[television]

We were told recently that AMG engines do not have a MAF thats why I did not answer the post

 

[Bolide]

The RAC man guessed at maybe something to do with a build up of gases in the catalytic converter or possibly something to do with the turbo

Grateful for any pointers. Plus any suggestions whether any of the hometune type organisations would be worth considering for a fix?

Obviously he was intent on upholding the technical standards of the RAC...

Utter nonsense and I would suspect that the home tune companies would display a similar level of ignorance & lack of suitable equipment

You need a good independent Mercedes specialist with a Star machine or a main dealer

Whereabouts are you in the country? Someone may be able to suggest a specialist local to you

Nick Froome
www.w124.co.uk

 

[GCLTuning]

look's like the jokers are out ! by the way nice web site ! did'nt know "home tuning" company's had Rolling Roads and a temperature control'd cell. Guess that won't do !

Im not a merc grease monkey. We write software (I think enough has been said let call it quits , not put each other down and stic to what we all know)

Kind Regards GCL Tuning

 

[Uncle Benz]

We were told recently that AMG engines do not have a MAF thats why I did not answer the post

The supercharged AMG engines do not have a MAF, but the supercharged engine was not fitted to the S55 AMG until 2001. 2000-2001 models will be fitted with the normally aspirated 367hp 5.4l V8 engine, which does have a MAF sensor. It is close-coupled to the throttle body.

 

[jberks]

Whether it has a MAF or some other method of airflow sensor it still boils down to the same thing. It drops into safe mode for some reason which is reset when the car is restarted. Mere mortal motors like mine do this as a result of the MAF playing up but there are other causes. Either way, the fault should be logged so it needs reading by a MB specialist. It's probably not serious, just a simple sensor somewhere, unless the RAC man is right and the cat is blocked which is a possibility..

 

[carnut13]

Oh come on Slowstarter! ( and I dont believe you are that slow if you drive a SL55)

These cars are very complex and have a very sophisticated diagnostic system for just that reason.

Take your car to your local MB dealer and ask for a quote (NB not estimate) to fix your problem. They shouldnt charge you for this, and ask first, because if they do tell them no. If they dont, (my MB dealer doesnt) then you have the info to know what the problem is and decide to either have them to fix it or go to a good indie .( a negotiating position if you play it subtly)

As above, where do you live ?( or work ?) as this will help us help you with the right advice

 

[television]

Thank you Uncle benz for clearing that, And I just stress again that the MAF does not show up on STAR.

Having a MAF then this should be the fault and so well known.

Cheapest from a Bosch service agent at £145 and very easy to fit, but then there should be 2 MAFs on this car and one is failing

 

[slowstarter]

Thank you - thank you thank you all! What a superb set of responses. I am in Camberley Surrey if anyone can recommend a local specialist that would be fabulous. Thank you all again.

Martin

 

[television]

Ollie in Portsmouth is not too far and very very good

 

[slowstarter]

I wish it was an SL55 ! But it can be quite quick nonetheless. Apparently it is delimited whatever that means. Not brave enough to find out.

 

[slowstarter]

Ok - I've found what it looks like from pictures I've found online. Whereabouts should I be looking to find it? At the moment the whole engine looks like its shrouded in a great big AMG cover, but I'm game to have a go and unplug it if I can find it! Sorry to be such a non mechanic. Last major work I did was a hillman imp engine rebuild in 1974. (It did start first time after installation though!)

Thanks again for taking the trouble to respond.

Martin

 

[slowstarter]

I emailed and then phoned Oliver in Portsmouth last week. Arranged to drive down with a view to having him diagnose and fix the problem. I turned up this morning, expecting to have to catch a train home and then travel back down once it was sorted. Anyway, Ollie had ordered in the MAF sensor in advance, in the expectation that this was the problem - which sure enough it was. He diagnosed and fixed the problem while I waited and then billed me a very fair price.

And now the car goes like a rocket - in fact, now I know what it is supposed to go like, I realise it wasn't even 100% when I bought it two years ago! (And I thought it was good then!)

So case closed guys. Thanks to the contributors on the forum, not only have I found someone local enough who really knows their stuff and charges reasonable prices, but I have my car back, better than I have ever known it. Thank you all.

Martin

 

[colechelle]

All good then!!! yeah, he,s a good lad!!!

 

[stumpy]

I changed MAFs on an M5 of mine and like you was struck by the improvement. I think the deteriation is so gradual you don't really notice it happening, until failure of course.

 

[bigasotonuk]

Glad you got the problem sorted.