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Mercedes Benz CLK 230K 1999 - Will not rev and very flat when supercharger cuts in - Fixed #

Posted by Ian Staples on October 16, 2009, 11:03 pm

Year of Manufacture *: t reg
Engine Code or Type *: ?

Got this merc, 208 chassis, 230K on a t-reg. Will not rev, goes very flat. Its ok on light throttle but open it up a little and it wont rev, it seems to be linked to the supercharger clutch, it comes in and it goes flat with a booming sound in the air filter box, air flow reading doesnt appear to drop off. There was loads of faults, all cleared ok except for the brake light switch, replaced the switch and that fault went away but still wont rev. No faults coming up.

Any ideas people? If ive missed out any info i'll add it or find/measure it as anyone mentions it.

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on October 16, 2009, 11:52 pm, in reply to "Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Kevin Apps

Ian
RE: Missed info!! check posting guidelines above your post, does your post tick every box.
Kev.

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Ian <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1121' width='330' height='300' border=0 style='border:none;'> on October 17, 2009, 12:08 pm, in reply to "Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Ian Staples

Oh very constructive comment, YES IT DOES !

Vehicle details are there, ive included tests/work carried out, any faults that are present, etc. If ive not put a measurement or test in my post its because i need a direction to look in first, especially with no faults present, isnt that the idea of this site, you put your fault on, people make suggestions, you go away and test/try what they suggest, you come back with answers !!!

Havent you got anything better to do than post comments like that !

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Pete Mutlow <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1569' width='330' height='300' border=0 style='border:none;'> on October 17, 2009, 1:46 pm, in reply to "Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Peter Mutlow

Hi Ian,

Will this vehicle rev in neutral or is it just when driving? Is it possible to do a vacuum check on it - I am thinking possibly of a blocked exhaust. Any emission figures at idle and fast idle might present a clue. Also what makes you think it is the super-charger clutch causing this problem? Any history on this? ie did it happen all of a sudden or previous repair work that might have generated this fault?

Regards

Pete M

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on October 17, 2009, 4:27 pm, in reply to "Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Kevin Apps

Ian
It would have been nice to know what codes you deleted (they may be relevant), Scanner used ? Emission,s ? Have you checked for exhaust back pressure ? What is the boost pressure ? Booming noise when the supercharger cut,s in seeems to suggest the supercharger clutch is working ok.
Kev.

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Alan Kane <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5535' width='330' height='300' border=0 style='border:none;'> on October 18, 2009, 8:29 am, in reply to "Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Alan Kane - Administrator

Kevin, Ian is the man with the car, not you. It is usual for these to have multiple codes stored which are irrelevant to an issue being looked at. Since they have cleared and not come back since the symptom has reoccurred then there is little chance of them being the relevant. The man is asking for a direction for his diagnosis and what he should check. Nothing wrong with that.

Ian, put it through a number of drive cycles if you have not done so already and see what, if any, codes come back. In the absence of codes I think your next step should be live data when the fault occurs. If it is flat then something will be wrong in live data. That system should show desired and actual boost figures.
Chech the O2 sensors and maf connections for oil ingress.

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Kevin Apps <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2589' width='330' height='300' border=0 style='border:none;'> on October 18, 2009, 3:02 pm, in reply to "Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Kevin Apps

Alan.
I agree, Ian is the one with the car, but he is also the one seeking help. So anything he can post removes a bit more of the blindfold from any-one trying to help, as we cannot see/ hear the car.
I hope this explain my view,s, as i am only trying to help, which i often do via e.mail to save hassle.

Regards
Kev

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Ian <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1121' width='330' height='300' border=0 style='border:none;'> on October 18, 2009, 5:55 pm, in reply to "Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Ian Staples

Hi all. Thanks for the constructive comments. Yes it is a direction im looking for, i do normally do extensive tests as i dont like to be beaten, but then normally you have some direction, fault codes, spark, fuel, etc, but this looks like it could be something simple yet spend a long time chasing as no fault codes are stored and live data looks ok.

I cant do a drive cycle as its undrivable, its all you can do to move it across the yard. Thats why i attended to the brake light switch fault first as ive had a few vehicles that wont rev or drive because the ECU thinks the brake is applied and it says you cant drive and brake at the same time, lol.

The engine revs up well until the throttle pedal position gets to a certain point, just open slightly, then the supercharger cuts in and it goes really flat with a booming sound in the air box. Airflow reading does not fall off, it increases well until the supercharger cuts in, then stays at that point.

I will do a gas check tomorrow if i get time. Also want to look at the fuel pressure. As far as i know this fault happened all of a sudden.

Looks like im gonna have to spend time on it, if the customer will let me. Will keep you up to date as i do the tests.

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Steve Scott <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1705' width='330' height='300' border=0 style='border:none;'> on October 18, 2009, 7:20 pm, in reply to "Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Stephen Scott

Hi Ian,

Sounds like an airflow issue to me, I would look very carefully at the inlet system to see if the intake is collapsing at some point when the charger kicks in.

It may also be worth dropping the front pipe/s to see if the exhaust is restricting the extra gas flow.

Hth

Steve...

Autoelectronix UK Ltd.
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Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by dave mc gee <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1044' width='330' height='300' border=0 style='border:none;'> on October 18, 2009, 9:11 pm, in reply to "Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"

Hi Ian,
Can you disconnect the charge to rule it out ?

Cheers,
Dave.

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Vince Mosley <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2919' width='330' height='300' border=0 style='border:none;'> on October 20, 2009, 12:07 pm, in reply to "Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Vince Mosley

Ian ,
Can you do a vacuum test first of all to see if all is as it should be? I had a supercharged XJR in a month ago that had very poor performance and would not rev above 2k and it was blocked cats and CPS. Cats diagnosed with vacuum test. MAF would be another area as have had all sorts of symptoms on Mercs caused by them.

Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in

Posted by Kevin Bain on October 20, 2009, 6:15 pm, in reply to "Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Message modified by board administrator October 21, 2009, 3:27 pm

Ian,

Some live data would help build a bigger picture. Can you pull LTFT and STFT values and lambda values on throttle. 4 gas would also be usefull. You say problem is on light load at a particular pedal position, I would have a look at the pedal sensor supply ground and the 2 signal cables. Note that this is a PWM signal where the frequency increaces with throttle operation.

Fixed #

Posted by Ian Staples on November 1, 2009, 9:47 pm, in reply to "Re: Mercedes CLK 230K, T-reg, will not rev and very flat when supercharger cuts in"
Message modified by board administrator November 2, 2009, 10:49 am

Hiya all

Thanks for all your comments. Ive been away from this one for a little while, had man flu and knocked me out, had to have a day off work and i can count on one hand how many days ive had off work from being ill. Had to put work off and then catch up a few days later. Anyway, never mind.

Gas readings were ok except the oxygen was a little high when the fault was present. No fault codes coming up though. Airflow looked good for the amount i could rev it. Dropped the exhaust off and after a bit of coughing and spluttering got it to rev to the rev limiter, about 4100 rpm, then after that you could gently rev it to the rev limiter. Put the exhaust back on and same thing, you could rev it to the rev limiter and hold it there bouncing around at 4100 rpm, gas reading was good and oxygen was low. Took it for a drive and it wasnt too bad but had a bad misfire under load, felt like ignition breakdown. This time it logged misfire faults. Changed the two coils and it drove fine. Guessing the coils were breaking down and caused the cat to block slightly. Im guessing the supercharger coming in was creating too much for the spark.

Why did it not log a misfire fault, or any fault for that matter, when it wouldnt drive or rev.

Anyway, thanks for all the ideas. Its all one big learning curve, which i enjoy, its just sometimes the cost (and sometimes the customer) means the diagnosis has to be correct first time.

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