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 Mike Your Own Question
Mike, Mercedes Technician
Category: Mercedes
Satisfied Customers: 39198
Experience:  Tech Expert
Type Your Mercedes Question Here...
Mike is online now

hi i am working on a S500 petrol 1999 140 series , first thing

Customer Question

hi i am working on a S500 petrol 1999 140 series , first thing in morining when u speed up to 40mph it looses power it then comes back very slowly , and there is not a problem till the next time it left for a few hours or the day , can u help
Submitted: 5 years ago.
Category: Mercedes
Expert:  Mike replied 5 years ago.
Hello and Welcome to justanswer..

My name is XXXXX XXXXX I'm happy to help / advise you on this -

What is the mileage on the vehilce?

What is its general service / repair history?

Do you get any fault lights come on when this happens?

Have you done any plug in tests at all ?

Rgds - MIKE.........................................

Customer: replied 5 years ago.
Hi mike, mileage is 90k and good service history, light on the dash did show a speed sensor other than that there are no other faults.
Many thanks Sean.
Customer: replied 5 years ago.
Hi do you have an update for me yet?
Expert:  Mike replied 5 years ago.
Hello again Sean -

I was awaiting your reply to the info request I sent you as above -

Ok re the speed sensor issue - have you done anything about that at all and / any other checks etc at all?

Rgds, MIKE....................................
Customer: replied 5 years ago.

Hi mike, I checked the distributor caps,sorry there is no distributor caps on this , could it be crank shaft pick up or crank shaft sensor?? Nothing else found but it is an intermittences problemi checked all wires rouns sensors , a ABS sensor would not cause this would it , there is a small tapping noise from the engine one of the tappits


Customer: replied 5 years ago.

hi mike any update.


Customer: replied 5 years ago.
Relist: Incomplete answer.
Customer: replied 5 years ago.

what is the story are u getting my mail . please reply

Customer: replied 5 years ago.
Relist: Incomplete answer.
i am still waiting for my answer
Expert:  Mike replied 5 years ago.
Hello again Sean -

Just to explain Sean - what happened here is... you responded to me as shown above...but before I had chance to reply - you put your question as a re list... which meant I was not notified any more of your communications... hence this is what has caused the delay... It just so happens no one else has picked up your question and it is presented to me again.. I hope that clarifies / explains why the delay etc in my getting back to you. Its the way the system operates , nothing to do with myself Im afraid.

As for the car - I know there is no distributor cap , I realised what you dont worry about that.

The problem with intermittent faults is that they can take time to find - sometimes hours - sometimes weeks and so on - You have to go on the symptoms to have the chance of tracing it successfully.

Given your symptoms, your most likely fault here with this Sean is the crank sensor... this is the main cause on this model of this issue that you describe. They basically break down internally and cause the engine to die - when it cools, you are away again.. So that is the biggest suspect here...

I would also advise though as well, check the exhaust system for any restrictions - this is best done with a back pressure test kit... just in case as they symptoms are similar. Let me know how you get on.

Let me know if you need anything else on this -

>> > Meantime -- Please click on the OK rating to Excellent ratings service for me now, Thank you for that... and you can get back to me any time if you need / wish..

Best Rgds, MIKE.

Please note, you are rating the content of my "answer" - my help to you - not the "system" which can experience delays etc which are not under my personal control -or delays caused by "time -off" which we all have on occasion - Thank you.