Mercedes-Benz Forum banner

41 - 46 of 46 Posts

·
Registered
Joined
·
329 Posts
Marcin, today I verfied, the EGR valves on the S600 V12 M120 engine, are actually CLOSED by vacuum.
went to my car, ran direct vacuum lines from each side of the manifold, to the EGR valves.
the car idled down lower than before, and runs much better.
it is now a rocket ship with the slightest touch of the throttle.
backing out of the driveway, it spun in the gravel a little.
flooring the gas, it really took off, then the traction control kicked in and pushed the gas pedal up a bit towards me,
because it was on the threshold of breaking the back tires loose.
run a direct vacuum line to your EGR valves, one on each side.
you must remove the airboxes and MAF sensors to do so, to gain access.
it will run better, it may fix it.
you may just have a broken vacuum line there,
of the electric switching module on each side of the intake manifold,
may not be working, and not shutting the EGR valves off.
it may also have a stuck open EGR valve.
 

·
Registered
Joined
·
2,323 Posts
@ Marcin Kismanowski,

Did you check your motor mounts as suggested by sc_rufctr?

I would not ignore his suggestion and it is very easy to verify.

My 1999 CLK had the exact same symptoms as your vehicle. It drove me crazy because it was temperature dependent. In my case, it did turn out to be motor mounts. As far as I could determine, it was caused by drop in engine idle speed once motor was warmed up and some harmonic reaction came into play with the reduction in engine speed.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #43
@ Marcin Kismanowski,

Did you check your motor mounts as suggested by sc_rufctr?

I would not ignore his suggestion and it is very easy to verify.

My 1999 CLK had the exact same symptoms as your vehicle. It drove me crazy because it was temperature dependent. In my case, it did turn out to be motor mounts. As far as I could determine, it was caused by drop in engine idle speed once motor was warmed up and some harmonic reaction came into play with the reduction in engine speed.
A motor mounts are ok - it looks like an electrical problem.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #45
have your wife buy you a scan tool for Christmas this year...;)
I've found a reason of non stability. It was really simple - one of spark wires was broken. I still don'e understand how it could be. When cold wire works, when hot no... Normally it should be opisite.
It looks, that I was looking too deep...
Anyway thanks for help!
 

·
Registered
Joined
·
329 Posts
uh-huh....see, a scan tool would have picked that up in 2 minutes, as a cylinder misfire, it would tell you what wire it was too, they are a must have today, esp. with this engine
 
41 - 46 of 46 Posts
Top