w140 500 coupe power loss

[smoothcoupe]

hello chaps, great to join you...
i own a w140 500 coupe 1994 model...it has been family owned from approx 2 years old, and now has 115,000 miles on it.. the work recently done was a new air mass sensor was fitted...and a full service from a independant specialist(scotts autotec in leeds). the problem im having is on rare occasions at idle it seems to missfire ie when parked at traffic lights etc, the strange thing is that it sometimes does not do it at all for a few days...the other thing is that under full throttle ie kickdown, the car seems to hesitate as if its holding back, it hesitantly reaches 4500/5000rpm and then doesnt change up a gear until i let go off the gas apart from this it drives fine,changes up and down fine silent and smooth until i put my boot down. it just doesnt seem as fluid as it should be...also on motorway above 70 mph the abs light comes on .can anybody please enlighten me. the car is booked in with the main dealer in leeds (derwents of leeds) for fault diagnosis only....any ideas chaps

 

[guydewdney]

my first suggestion is the dreadead wiring loom breakdown - pre 1996 cars have a bio-degradeable looms....

 

[jgevers]

Hi,

I would change cap and rotorarms as a matter of course. These will provide all sorts of missfire problems. Also I would check the wiring loom to the electronic throttle body. I have seen some 'green pustules' in these before.

Make sure you have good quality petrol and don't run the tank on almost empty all the time. A lot of condensation eventually will result in a lot of water in the fuel.

regards,

Job

 

[smoothcoupe]

w140 coupe.... suggestions

hi guys,, my 500 coupe went for fault diagnosis to dealers today about the hesitation problem...they told me it was put on the testbooks and no fault was found, the dizzy caps,air mass sensor was replaced all to no avail...however they said the fuel pump/fuel could make a difference....i was actually thinking the fuel pump was alittle noisy(loud hissing )is this normal....are they talking sense or feeding me sh**...they didnt mention any thing regarding the wiring harness breakdown of these cars...

 

[smoothcoupe]

s500 coupe.went to dealers today

my 140 500 coupe went to dealers for fault diagnosis today.. they said no fault was found.. and the slight missfire and power hesitation could be down to fuel pump/filter. are they talking shi** ... they didnt mention nothing about the wiring harness breakdown...they told me this guys been on tools for 25 years..

 

[Bernie Cook]

Although I run a W124 E320 (not a W140 500 coupe), I have been warned that if I experience anything similar to what you are getting, have the engine wiring harness checked out first.

If the harness malfunctions, I have been told that it can screw up the various systems located under the bonnet including any of the ECUs and in turn, this will screw up your wallet big time.

After checking out the wiring harness, have the solderd joints in the voltage protection relays examined.

 

[Dieselman]

After checking out the wiring harness, have the solderd joints in the voltage protection relays examined.

I was going to say that!!

 

[smoothcoupe]

voltage protection relays.

hello. can any one tell me where the voltage protection relays are located on my 1994 s500 coupe...

 

[frog1520]

hello chaps, great to join you...
i own a w140 500 coupe 1994 model...it has been family owned from approx 2 years old, and now has 115,000 miles on it.. the work recently done was a new air mass sensor was fitted...and a full service from a independant specialist(scotts autotec in leeds). the problem im having is on rare occasions at idle it seems to missfire ie when parked at traffic lights etc, the strange thing is that it sometimes does not do it at all for a few days...the other thing is that under full throttle ie kickdown, the car seems to hesitate as if its holding back, it hesitantly reaches 4500/5000rpm and then doesnt change up a gear until i let go off the gas apart from this it drives fine,changes up and down fine silent and smooth until i put my boot down. it just doesnt seem as fluid as it should be...also on motorway above 70 mph the abs light comes on .can anybody please enlighten me. the car is booked in with the main dealer in leeds (derwents of leeds) for fault diagnosis only....any ideas chaps

My 97 S320 had exactly the same symptoms a couple of weeks ago. Turned out to be a dodgy HT lead.... Good luck!

 

[grober]

hello. can any one tell me where the voltage protection relays are located on my 1994 s500 coupe...

You should really check out this site. http://pages.prodigy.net/jforgione/MB_S500.html It deals with Jims S500 coupe but the content has much wider applications.