S420 spluttering, misfiring, brown exhaust, and HOT

[ychachad]

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.

[wildponey]

wow.....that sucks!......i wish you luck on your car...sorry if im not being helpfull

[jhodg5ck]

What year is your 420 and how many miles? If this is a early/mid 90's benz w/ close to 100K Please don't base your thought on all of them, you have one of the cluster F*&^ years of MB..

Let me know, your problem could be a few different things, wiring harness, air valves etc, etc..

Jonathan

[barry putnam]

[:)]
just a guess, but check your radiator, is it full? I suspect a coolant fluid leak, but from where? I wouldn't be surprised if you have a blown head gasket.
Get a compression check, that might tell you if one cylinder is low, and where to look for a leak.

Barry

[ychachad]

Mine is a 1995 S420 with 78k miles, thanks for the reply. What I am flummoxed about is the fact that I have rarely used this machine when the problem developed. And since it is rarely used, the new battery is disconnected most of the time. Does this change computer processes? Does this reset something? Please help.
BTW, that is my quarrel with MB. No car ought to be a cluster funk, regardless of price, and least of all a $80K MB S-class.

jhodg5ck - 10/7/2004 9:56 PM

What year is your 420 and how many miles? If this is a early/mid 90's benz w/ close to 100K Please don't base your thought on all of them, you have one of the cluster F*&^ years of MB..

Let me know, your problem could be a few different things, wiring harness, air valves etc, etc..

Jonathan

[///S320]

Check for ignition coils for up and down revs..

[pcmaher]

Curious why you're disconnecting the battery. I've read in other posts that all sorts of weird electrical gremlins can pop up if you disconnect the battery.

[jhodg5ck]

Well, pulling the battery leads can sometimes sort out issues, but yes, I have known it to generally cause more then it fixes. At 82K, your harness should be OK, but it is getting close to the 100K mark (where most harnesses in early/mid 90's mercs like to go). It sounds like you are having a fuel delivery issue, my 560 did something very similar and it was the KE contron unit for the fuel injection.. What I have found is that cars will swith off warm up mode, go to tlook for the appropriate signals (O2, air mass etc..) but for what ever reason can't process the info, giving the injection system worthless info. I think your best bet given the electronic nightmare that can be 140's would be to get it to your dealer, or anyone that has a code reader for it, and have it on the machine when it is acting up. You may have a malfunctioning sensor throwing you off etc..

Lastly, MB's hate to sit.. The more they sit, generally the more problems will arise.

Let me know what you find!
jonathan