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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 54036
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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I have a 1990 300 SE and i had some idle issues and now that

Customer Question

i have a 1990 300 SE and i had some idle issues and now that it seems like they have fixed it, Im not too sure. When driving in the freeway the rpm seem to be steady at about 40 when driving about 70mph. Is this normal???
JA: How many miles are on the car? What size is the engine?
Customer: v6 85,ooo original miles.
JA: What is the model/year of your Mercedes?
Customer: I meant straight 6
JA: What year is your Mercedes?
Customer: 1990
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I'm having it fixed at meineki
JA: Anything else you think the mechanic should know?
Customer: no
Submitted: 1 year ago.
Category: Mercedes
Customer: replied 1 year ago.
straight 6 cyl. 85K original miles
Expert:  Marty replied 1 year ago.

Hi, the older Mercedes usually run high rpm at freeway speeds. A simple test is to manually move the shifter from D to 3 and see if the transmission downshifts. Do this at 40 mph after you feel the transmission has finished shifting through the gears. If the transmission drops down a gear when you pull back on the shifter it tells you that the transmission was in 4th gear and that the rpm you are seeing is normal.

Let me know if you have any questions.