How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Matt Your Own Question
Matt, Engineer
Category: Mercedes
Satisfied Customers: 21708
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
Type Your Mercedes Question Here...
Matt is online now
A new question is answered every 9 seconds

Have a 1985 Mercedes 500 SEL. Starts fine but will idle down

Customer Question

Have a 1985 Mercedes 500 SEL. Starts fine but will idle down in a minute or so running rough with black smoke coming out tailpipe. Have to hold down accelerator down to idle about 1500 RPM for about a minute or so until the engine idles fine. This happens after each shutdown
Submitted: 1 year ago.
Category: Mercedes
Expert:  Matt replied 1 year ago.


I'd say this sounds like the warm up regulator is sticking ( item 8 in the image)

as its the mechanical fuel injection system K-jet on these

I'd suggest that the regulator needs stripping down and cleaning to ensure it moves freely

if its badly corroded it may need replacing