Idle speed diagnosis
#1
12-28-2006, 01:32 AM
Idle speed diagnosis
My '01 E320 has been idling weird lately, it sounds good and then it revs up about 300-500 rpm for a pretty constant time and then comes back down...its real strange because its so constant, like you can set your watch by it its runs revs runs revs....like super consistent and patterned....any idea on what may be causing it
also best shocks for this car if you want a smooth ride
thanks guys
also best shocks for this car if you want a smooth ride
thanks guys
#2
12-30-2006, 03:08 AM
RE: Idle speed diagnosis
Sorry you didn't get an answer but I don't contribute to this site to the exclusion of everything else in life.
The reason i haven't replied to your posts is that either I've been busy or the definition of your problem has been insufficient to respond or I just don't know the answer.
However I'll see if I can move the idle problem forward for you and try to show you some of the things that go through a respondents head when faced with a question like yours.
My '01 E320 has been idling weird lately, it sounds good and then it revs up about 300-500 rpm for a pretty constant time and then comes back down
Mileage?, last service?, serviced by?, how long have you had the car?, anything happen at the time the problem started?, Check Engine Light CEL ON?, only when cold or also when hot? other symptoms? etc. etc. etc.
First step is to get the Diagnostic Codes (DTC's ) read either by a garage or DIY if you have an OBDII 16 pin CAN compliant scanner.
Your problem is "regular as clockwork" since the change in engine speed is being controlled by the Engine Management System EMS. The issue is which of the many sensor inputs to the EMS or the controlled outputs is not working correctly.
The EMS does a startup check which if not achieved satisfactorily will illuminate the CEL. Likewise if a problem occurs during running then a DTC will be set which may or maynot illuminate the CEL.
At present there is insufficient information to even hazard a guess as to the cause since there are so many unknowns.
Since you have previously raised the issue of fitting Distronic (Cruise Radar) to your car I have to assume that you are an enthusiastic and competent individual when it comes to DIY on your vehicle. I made the assumption....possibly incorrectly...that you would know to get the codes read. You certainly should have picked this up as a first stage if you were to read a few posts with similar/same symptoms.
Incidentally unless you have very deep pockets don't even consider trying to fit Distronic yourself! It can be done just like COMAND but you will need main dealer support to configute the system once you have plugged all the (expensive) bits in....and don't forget...... Distronic has the potential to create an accident!
Hope this helps. I await your response and additional information.
The reason i haven't replied to your posts is that either I've been busy or the definition of your problem has been insufficient to respond or I just don't know the answer.
However I'll see if I can move the idle problem forward for you and try to show you some of the things that go through a respondents head when faced with a question like yours.
My '01 E320 has been idling weird lately, it sounds good and then it revs up about 300-500 rpm for a pretty constant time and then comes back down
Mileage?, last service?, serviced by?, how long have you had the car?, anything happen at the time the problem started?, Check Engine Light CEL ON?, only when cold or also when hot? other symptoms? etc. etc. etc.
First step is to get the Diagnostic Codes (DTC's ) read either by a garage or DIY if you have an OBDII 16 pin CAN compliant scanner.
Your problem is "regular as clockwork" since the change in engine speed is being controlled by the Engine Management System EMS. The issue is which of the many sensor inputs to the EMS or the controlled outputs is not working correctly.
The EMS does a startup check which if not achieved satisfactorily will illuminate the CEL. Likewise if a problem occurs during running then a DTC will be set which may or maynot illuminate the CEL.
At present there is insufficient information to even hazard a guess as to the cause since there are so many unknowns.
Since you have previously raised the issue of fitting Distronic (Cruise Radar) to your car I have to assume that you are an enthusiastic and competent individual when it comes to DIY on your vehicle. I made the assumption....possibly incorrectly...that you would know to get the codes read. You certainly should have picked this up as a first stage if you were to read a few posts with similar/same symptoms.
Incidentally unless you have very deep pockets don't even consider trying to fit Distronic yourself! It can be done just like COMAND but you will need main dealer support to configute the system once you have plugged all the (expensive) bits in....and don't forget...... Distronic has the potential to create an accident!
Hope this helps. I await your response and additional information.
#3
01-24-2007, 01:08 AM
RE: Idle speed diagnosis
I have an older 300E from 1987 and I was having this issue too, mixed in with a little hesitation when I was starting from a stop...I took it to a Mercedes shop and had someone go out for a ride with me so I could hear/feel what they felt/heard...they diagnosed it as worn wires and spark plugs and so instead of paying them to do that simple job for me I got the parts myself and replaced everything and it totally fixed my problem
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