Hi all,

I'm hoping -someone- has had this problem before, and more to the point, found a solution.

I've a 2000 CLK430. It had been driving pretty well for the past year, but a couple of months ago, a few things seemed 'off'.

1. Start the car without any trouble, but there is a tappy sound from somewhere in the engine itself (not any of the drive belts from what we can tell)

2. When the engine is at idle, its sweet, but when you rev it to just over 1k rpm, the car has a very distinct 'judder' every time, no matter if the engine is hot or cold.

3. When driving, it is fine, until you drive that little bit harder and approach the 4k rpm, then something very weird happens (no matter what gear you are in)... The car feels as if someone has just hooked a caravan onto it (and a quick look in the rear-view mirror confirms that there is in fact, no caravan! ) there is a drop in power and even though my foot is planted to the ground, there is no more life in the engine for a good 2 seconds or so, and then....WHAM....you get a new lease of power (sometimes, but not always) and it gets up past the 4k rpm mark and continues on up until you change gear again.

I've had the car fully serviced (seemed the fuel filter had possibly -never- been changed) and put in 16 new spark plugs, 16 new HT leads and even changed one injector and one coil pack (as a trip to Mercedes confirmed that Cylinder 6 wasn't operating correctly (misfires aplenty)).

Nothing but nothing has cured the problems stated...

Anyone ever come across this before?

Ps. Can I take this opportunity to say that I know there is a 4000 rpm limit when the car is in Park or Neutral mode etc etc. The issue I'm describing is when you are live, on the road and driving. Not parked! Ta

 

my guess is that the spark plug wires are not fully on the plugs or the coils. you really need to push them on until they click.. i use a prybar to push them on the sparkplugs. and sometimes when you put them on the coil packs they or still not fully seated.. i spin the wires onto the coils and pull gently to make sure they are tight......the power loss issue sounds like mass airflow sensor. you should be able to rev to redline in gear. only at idle is there a 4000rpm rev limit

 

Hi ya! thanks for your reply.

I did actually take all the plugs out and the cables and reconnected everything again. The MAF had been changed two times on the off chance that i may be related, but still no better... hence going insane!

 

maybe you have bad motor mounts they are a common failure on bezes.. maybe your feeling the engine vibration threw the body..

 

Thanks for the interest.

I know where you are coming from, and so I've organised for my mechanic to inspect my engine mounts. Maybe they are worn and this is just helping to amplify the vibration that the engine is making.

Obviously, worn engine mounts wouldn't create the misfires etc though, so I will still have that issue regardless.

Thanks for your input.

 

if you take it to a dealer they will tell you exactly which cylinder is misfiring. you could also have a vacuum leak from some vacuum hoses maybe and EGR issue, a sticky valve ..you say the car wont REV over 4000 at all all the time? maybe you have bad CATS clogged up?

 

Yeah, I did take it to a dealer mechanic and he plugged it in for me. The problem appears to reside in cylinder 6 and to a lesser extent, 3.

When doing a Smooth Run test, all 8 cylinders fire in normal sequence of 0, 1 ,2 then back to 0. Cylinder 6 goes '0, 1, 2' and then stays there.

Cylinder 3, does work, but isn't as quick to respond as the other cylinders.

Concentrating our efforts on cylinder 6, we changed the injector, then the HT leads, the the coil pack and still no better.

Would there be a sensor problem somewhere?

I am beginning to wonder about an issue with the CAT at this point... but big money if it is, so wanna count out other possibilities first.

I've been trying to get the Merc back onto the computer for diagnostics, but various issues outside of my control are hindering my appointment at present (Mechanics missus having a baby!)

 

*Bump.

Any ideas on this guys?

Computer still says im misfiring on cylinder 6?!

Cylinder 6 has had a new injector, new coil, new plugs and new leads!

What could still cause a misfire to one cylinder after all the above change outs?

 

i have 2000 clk 430 coupe, it has been 3 years I did not start the car, this may i was planning to take the baby out,Guees what friends telling me, do not start the car you need to take the spark plugs off librucate them with the oil, crank the engine anddddd since its been 3 years they are telling me my fuel is no longer good, i need to drain the fuel and change the fuel filter, oh my god what a mess I created.if I dont change the fuel filter and drain the old fuel I will be ruining my fuel injector system, is that true? what should I do here? my car only has 13000 miles. never seen rain and snow, still show room condition. thanks

 

SHEA,
at this point i would check cats as chassis said in closing , you can pull out O2 sensor on each side and use back pressure gauge its a go no go test .
Jerry
p/s do youdon't have after market air filters in car do you ? / or anything blocking air flow just a thought saw this before too