S420 spluttering, misfiring, brown exhaust, and HOT
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Member
Joined: Dec 2002
Posts: 78
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From: Pittsburgh, USA
1995 S420
S420 spluttering, misfiring, brown exhaust, and HOT
My MB S420 had recently started acting erratically (instead of erotically, as it should). At first it spluttered a bit, but then ran fine. In the past few days, the car starts up fine, but as soon as it warms up, it begins to splutter, the revs go up and down at idle. If I rev it, it splutters and misfires heavily, starts blowing "brown" smoke, and then the temperature starts rising well past the 80 mark (which it normally ran at). The exhaust gas temperature is unbearably HOT to the feel. This is when I immediately shut it off, and allow it to cool with the hood open and the heater running (to get heat away from the engine). Several hours later, once cool, the car starts up fine, but within minutes, as soon as the car warms up, the procedure repeats itself.It has had a recent tune up with new air filters, spark plugs, new battery, fuel filter, etc. Any ideas? I don't think it will make it to a mechanic if I try to get it on the road. I may have to tow it. Please help!!! This car is relatively new, with relatively few miles. Always properly dealership maintained, always garaged. The A/C is also KAPUT!!! As much as I love it, this will be my first and final Benz. Thanks in advance.
Member
Joined: Dec 2003
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first thing i would replace is the temperature sensor on the front of the engine between the V's - there are severla types, and on some cars several sensors there..
on my 96/97 420 the sensor was 20 UKP = 30? USD
edit - yours is part number 008 542 45 17 = 27 USD and is the smaller one at the left of the bigger one at the front of the engine.
on my 96/97 420 the sensor was 20 UKP = 30? USD
edit - yours is part number 008 542 45 17 = 27 USD and is the smaller one at the left of the bigger one at the front of the engine.
Last edited by guydewdney; Oct 7, 2004 at 06:52 PM.
Thread Starter
Member
Joined: Dec 2002
Posts: 78
Likes: 0
From: Pittsburgh, USA
1995 S420
Thanks for your reply and the time you took to get the PN. I shall look into it.
Originally Posted by guydewdney
first thing i would replace is the temperature sensor on the front of the engine between the V's - there are severla types, and on some cars several sensors there..
on my 96/97 420 the sensor was 20 UKP = 30? USD
edit - yours is part number 008 542 45 17 = 27 USD and is the smaller one at the left of the bigger one at the front of the engine.
on my 96/97 420 the sensor was 20 UKP = 30? USD
edit - yours is part number 008 542 45 17 = 27 USD and is the smaller one at the left of the bigger one at the front of the engine.
Newbie
Joined: Jun 2005
Posts: 4
Likes: 0
From: TX
1996 E320
same problem
The same problem happened to me this morning. Car ran fine after start up from cold....got on the interstate...took my same exit...and as I came to the stop light, I noticed the brakes were harder to press...then I pulled into my employee parking lot and got the erratic idleing...up and down...I was thinking I must have nocked a vaccum hose loose... went out at lunch and I have no idea what vaccum hoses go to what...anyone have a diagram? I have used the search to no avail...
Senior Member
Joined: Dec 2002
Posts: 419
Likes: 1
From: Sunny Naples, FL
2018 GLS63 AMG
It sounds like the Electronic Throttle Actuator. I had a similar problem with my S500 coupe and it was not cheap to fix 
(I sold the car after I fixed it). It seems to be a common problem with the earlier V8 w140s.
(I sold the car after I fixed it). It seems to be a common problem with the earlier V8 w140s.
