weedy C43 AMG

[frostbite]

Ok just bought it and it's lovely. Private buy and it was on a sorn so impossible to do full road test.
Drove home in the dark didn't realise it was in W mode, put it in S today hoping for more more poke, no, tried manual gear changing, no.
Gear box seems to work fine, it's just that you'd swear this was a 80 bhp car. Revs ok, a little teeny bit rough at idle if holding it in drive on the brake. Just seems to be weedy.
Done all the usual things like examine the oil, water, oil filler cap for blow-by etc and all good. No 'management lights' on. The accelerator does feel like there's a mile of slack in the cable, so I'm only getting a half open throttle, but it's drive by wire?
Any ideas for the first thing to poke at? Booked in to MBTech in Warrington for a good checkover, but that's a couple of weeks away.
I'm reasonably good at home mechanics, and not afraid to tackle anything, but I obviously don't have all the fancy equipment and diagnostics. Nor have I worked out where everythin gis yet or how it all goes together...
Yes I know, you're all going 'Ooooh dear!' and sucking air through your teeth, but I'm hoping someone will say, 'It's the little sensor thing on the left, just hit it with a half-inch ring spoanner and it'll go like a scalded cat!'

 

[KillerHERTZ]

MAS need replacing?

 

[MancMike]

If you're cruising at 30, so the car drops into high gear, 5th probably, what does it do if you slam all the way through the kickdown? Does it drop 3 cogs and launch? Does it downshift at all? Maybe the kickdown button is faulty?

Have you tried resetting the pedal?

 

[nb_racing]

MAS need replacing?

2nd

 

[frostbite]

Thanks for replies chaps, I haven't even looked under the bonnet yet. First job will be to have a good look at the pedal set up. Bit reluctant to splash out on new MAS until plugged in to diagnostics, although seems to be a likely suspect. I believe anything cheaper than MB or Bosch MAS sensor is a false economy?
I may try soakling it in Cola first (worked on my Ford diesel!)

 

[The _Don]

One more here for the maf, treat your 43 to a new bosch unit.

 

[grober]

If not the MAF if its "drive by wire" you might have problem with the throttle actuator assembly . Other possibilities you need to change the fuel filter or you have a partially collapsed catalytic converter/s.

 

[nb_racing]

If you unplug the MAF and it makes no difference to how the car is it is most likely dead.

 

[frostbite]

If you're cruising at 30, so the car drops into high gear, 5th probably, what does it do if you slam all the way through the kickdown? Does it drop 3 cogs and launch? Does it downshift at all? Maybe the kickdown button is faulty?

Have you tried resetting the pedal?

kickdown works fine - just doesn't go very fast. Kickdown does seem to be wanting more to happen (like power flooding in) but does change gear in a sort of 'oh ok then' manner.

 

[KillerHERTZ]

kickdown works fine - just doesn't go very fast. Kickdown does seem to be wanting more to happen (like power flooding in) but does change gear in a sort of 'oh ok then' manner.

Exactly what a dodgy MAS does.

 

[Auto-mobile]

As stated replace the air mass sensor, you can soak it in coke/oil/gold infact whatever you like but if it's failed it won't fix it, and the throttle cable is adjustable, under the bonnet next to the brake fluid reservoir.

 

[BlackC55]

As stated replace the air mass sensor, you can soak it in coke/oil/gold infact whatever you like but if it's failed it won't fix it, and the throttle cable is adjustable, under the bonnet next to the brake fluid reservoir.

The air mass sensors are not expensive either. I don't understand why people want to clean
them.

The throttle adjustment is on the other side.

 

[frostbite]

Well, the sun is shining and I have a day off when it's not dark all the time I'm at home. Found the throttle adjuster, bit slack, so a few turns and that's sorted. Airbox off and found filthy filters and enough leaves to hibernate hedgehogs and keep Bayleaf busy from early dawn. Found the MAF...... and reconnected the plug! Goes very much better now! Ordered some K+Ns and probably the plugs need replacing too. Now have a long 'to do' list of clean this, grease that, a good Gunk/jetwash and ACF50ing and she'll be looking much nicer. Much happier with my purchase now! Thanks for all the pointers!

 

[nb_racing]

Well, the sun is shining and I have a day off when it's not dark all the time I'm at home. Found the throttle adjuster, bit slack, so a few turns and that's sorted. Airbox off and found filthy filters and enough leaves to hibernate hedgehogs and keep Bayleaf busy from early dawn. Found the MAF...... and reconnected the plug! Goes very much better now! Ordered some K+Ns and probably the plugs need replacing too. Now have a long 'to do' list of clean this, grease that, a good Gunk/jetwash and ACF50ing and she'll be looking much nicer. Much happier with my purchase now! Thanks for all the pointers!

You need a 55 engine. Believe.

 

[frostbite]

You need a 55 engine. Believe.

Hmmm, maybe one day. I have another baby that's first in the queue, that's been promised a suspension upgrade and a six-pot front caliper.....

Where does one find a 55 engine in good shape anyway (without actually buying a 55)? How much else would I need from a donor? No, no, don't answer, I really can't start thinking about it at the moment.

 

[nb_racing]

There might by one coming up for sale very soon.
It drops straight in and runs on the standard Ecu as it self adapts. The starter motor swaps sides and that's it. There is something I think on some engines with a water heater inlet???

My one was figured 0-60 4.9 on a vbox. Not that I like to mention that very often. There are quite a few and I don't think anyone regrets the conversion.