230 slk being lazy

[roscoc180]

Can anyone help me, i have a 230 slk 1998 and sometimes after a while it lacks acceleration and seems quite slow. If i stop, turn the engine off and start again it's back to it's normal self ???????????????????
Would appreciate any ideas

 

[roscoc180]

Just thought i'd add something myself. After driving to work for two days i have noticed that if i drive over *******speed humps very slowly my problems do not occur, is there a sensor or something that could case the car to be sluggish after a sudden movement.

 

[jberks]

In a word - no.
The normal place to start is with the MAS sensor.

 

[roscoc180]

Hi thanks for that but can you tell me what that is? Can this sensor reset it's self when i turn off the engine and start again. The other day i had the sluggish problem and stopped and restarted and then drove 80 miles without a problem. Thanks for any advice

 

[jberks]

Hi,
The MAS (AKA MAF) is the Engine's airflow sensor. It tells the computer how much air is coming in so the computer can calculate how fuel to add. These are by far the most common cause of problems. They wear out or get dirty and start mis reading. There is a section on here on how to clean them. Alternatively you can buy the inserts for them or finally a new unit from the dealer. The choice is yours. Fitting is a 10 min job.
If they (or other sensors for that matter) start sending spurious signals, the ECU will go into a default 'safe' mode to avoid doing any damage (as it can't be sure what's going on). This will manifest itself in engine warning lights coming on (sometimes not) and generally poor running and performance. Switching the engine off and on, resets the safe mode, so it will be fine until the next spurious signal.

The best route is to have the fault codes read from the ECU, but as I say, the most common cause is the MAS.

 

[roscoc180]

Thanks very much for your advice will do it this weekend. I was telling a mechanic freind of mine and he said to spray carb cleaner into the pipe to clean the MAF do you think this will work or is it better to follow the instructions on the forum? Again thankyou

 

[jberks]

I can't see it doing any harm, though a visual inspection first might be a good idea, just to see whether there is any much to clean off.

 

[roscoc180]

Hi all,

Printed the pics off the forum ready to go and attempt to clean my MAF, opened the bonnet to find it looks nothing like the one on the pics. I think my MAF is in a sealed unit????? If i take the airbox cover off a unit with two large pipes and a wire come off, with one inlet having a large butterfly. Does anyone know if this is the MAF and how can i clean it.

Thanks

 

[David in OZ]

Hi all,

If i take the airbox cover off a unit with two large pipes and a wire come off, with one inlet having a large butterfly. Does anyone know if this is the MAF and how can i clean it.

Thanks

The MAF in a 1998 SLK230K is to the right of the radiator (looking into the engine compartment) in a tube leading up from the intercooler

The unit with the butterfly is the air bypass valve....when this closes the air intake is via the supercharger......when open air intake is directly from the air box

The MAF is shown at mid right of this pic..........

David

 

[roscoc180]

Thanks David I can now start in the correct area of my engine bay!!!!!!!!!

 

[citroennut]

hi, as replied in another post, '98 e240 w210, i had a similar problem, the only difference is that it would only happen first thing in the morning when quite cold. no power, no acceleration but when switched off and restarted everything was perfect. it wasn't the maf as that had been replaced mercedes said it was a sensor but unsure which one as no faults logged. car was gassed and if run with it powerless until gas clicked in then problem disappeared so seemed to me to be fuel/sensor related. hope this helps.
cheers
simon

 

[roscoc180]

Thanks for that, I,ve just had the car put on a diagnostic test and it reads a fault with the supercharger circulation valve/air bypass valve. This is fixed to the airbox and changes the air intake from external or from the supercharger (i think) does anyone know if it can be fixed or where can i get a new one.

 

[David in OZ]

Thanks for that, I,ve just had the car put on a diagnostic test and it reads a fault with the supercharger circulation valve/air bypass valve. This is fixed to the airbox and changes the air intake from external or from the supercharger (i think) does anyone know if it can be fixed or where can i get a new one.

Can you post the code(s)

You will find that the Air Bypass Valve is quite expensive............worth a check of the asssociated wiring to the Kompressor control parts of the SLK

connection at air bypass valve
connection to Cam Adjuster Magnet....for presence of oil in particular
connection to Cam Position Sensor


David

 

[roscoc180]

Hi David thanks for your feedback, this might sound silly but i got home last night after finding out the new part was nearly £300.00 from mercedes and thought i would clean the MAF as per forum instructions and the car is going like it never has with no problems during the 20 miles to work (touch wood) so does a £6000.00 diagnostic set up promt you to spend £300.00 needlessly??? i wonder if a fault in the MAF could transpose as a fault somewhere else. Thanks again

 

[television]

Hi David thanks for your feedback, this might sound silly but i got home last night after finding out the new part was nearly £300.00 from mercedes and thought i would clean the MAF as per forum instructions and the car is going like it never has with no problems during the 20 miles to work (touch wood) so does a £6000.00 diagnostic set up promt you to spend £300.00 needlessly??? i wonder if a fault in the MAF could transpose as a fault somewhere else. Thanks again

Talking to one of the MB engineers a couple of weeks back, he said thay have to do what ever the diag tester tells them, this is a long way from common sense and reason.
What is wrong with the world, when it is change this and change that. I am surprissed that they do not replace the head lamps when they are dirty.

A new MAF from Bosch is £58 when the time comes and you put it in your own housing.

Malcolm

 

[roscoc180]

Hi all,

After two weeks since cleaning the maf it's playing up again. cleaned it again but still not accelllerating well (limp mode i think) turn off and start again and it's fine. i suppose i should buy a new one. does anyone know where i can buy one.
Thanks.

 

[angus falconer]

Hi all,

After two weeks since cleaning the maf it's playing up again. cleaned it again but still not accelllerating well (limp mode i think) turn off and start again and it's fine. i suppose i should buy a new one. does anyone know where i can buy one.
Thanks.

Looks like you can either (a) get the whole unit from Merc or (b) order the innards from Bosch/Bosch supplier and insert into the existing body.

Televison is suggesting (b)so I will defer to him on that option.

 

[David in OZ]

Was there any evidence of oil fouling of the MAF.......if so a good cleaning of the oil separator and intercooler might be required otherwise a new MAF might only last a few weeks also.................

Be careful of eBay MAF's.....take Malcolm's advice and get genuine Bosch MAF insert from a Bosch distributor......

Cheers

David

 

[television]

Hi all,

After two weeks since cleaning the maf it's playing up again. cleaned it again but still not accelllerating well (limp mode i think) turn off and start again and it's fine. i suppose i should buy a new one. does anyone know where i can buy one.
Thanks.

You have a Bosch service center at Newton Abbot 01626 36 36 30

WWW.monnington-motors.co.uk

Malcolm

 

[roscoc180]

thanks for all your advice

Ross