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#1
12-26-2003, 03:23 AM
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Going nuts...
TECH HELP 420E
I have a 1995 420e that has a weird problem. After the car sits for a couple of days it starts fine, but after about 10 minutes it runs very rough and without power as it it were only working on half the pistons. The condition seems to come on after reaching working temperature. While it is doing this it moves sluggish and stepping on the gas seems to "flod" it. The condition gradually goes away and after another 10 or 15 minutes it runs fine. If I drive the car daily it does not do it. It has to sit idle for 3 or 4 days. Very confusing...... 
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#4
12-26-2003, 08:57 AM
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O2 sensor?
Perhaps the O2 sensor is shot? I'm not sure about the E420 - but in other cars the O2 sensor doesn't activate until the exhaust warms it up. Perhaps it's not doing its job well and sending an erroneous signal to the engine after it warms up (your 10 minute time period) - causing it to run lean or rich.
No idea why it would occur after sitting for several days. Any thoughts from others? Troy 1995 E420
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#5
12-26-2003, 09:32 AM
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o2 sensors
I'm looking for some technical specifications on the various o2 sensors employed by MB. Personally, outside of the heater circuits and ground wire, do they all behave the same? I would find it strange that an automobile manufacturer would install a non-common sensor.
Let me be more specific. Do all oxigen sensors give the same reading (in voltage)? Don't know where to find the various specs. Ron
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#8
12-27-2003, 09:59 PM
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Is it cold where you run? (Long)
How old is the battery? Is it "winter" where you live? The next time you are allowed to let it sit for the 3 or 4 days, before you start it, check the voltage (or if you have a hydrometer, the specific gravity) of the battery. It should be close to 12.3-12.6volts (1.20-1.26 spec gravity), anything less may be hindering full current flow to your fuel pump. I believe the Powertrain control module richens the mixture when it's cold (at start until it warms up) by extending the pulse duration of your fuel injector driver. Which may hide the inadequacy of the fuel volume/pressure. Once it reaches operating temperature and in closed loop, then evidence of POSSIBLE low current is exposed. At least, until the Alternator has re-charged the battery to a decent output. Before digging into the fuel system, I'd conduct this little investigation. Nothing that will set you back if it proves the battery's OK.
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