RPM fluctuate

Asked by GuruVCLZY Aug 19, 2018 at 07:58 PM about the 2010 Audi S5 4.2 quattro Premium Plus Coupe AWD

Question type: Maintenance & Repair

Recently a tragedy happened to me. the story and the main problem of car are
described below. If you guys has any idea, pls help and let me know. thank
you in advance. have a wonderful day.  MY car is 2010 audi s5, 70000 mile

recently, the check engine light appear on dashboard, which is about intake
running tunning(runner control).  since my car is running well, i though there is
minor problem, i have my car repaired in local auto shop instead of dealership.
but that incompetent mechnical fail to repair my properly(i think he misinstall
the component). when i pick up car from them and drive it on highway. there is
loud noise comming from engine and car was shaking. so i send my back to
them and they fix it in next day.  they told me there is no problem, when i test
drive my car. i only can feel there is little difference but not noticeable problem(
no check engine light, gearbox light) so i just let it go.

after driving 500 mile later, the car has mainly suffered two problem:
Abnormal Coasting (only happened after letting off gas pedal), i have recorded
it and post it in youtube, PLS CHECK IT:  https://youtu.be/8SY4aJnAq40

When my car is running on high way, I hit the accelerator to 2900 RPM and
then let off the gas to let my car coast.  the rev drops and then FLUCTUATE
couple time. 

meanwhile , I can hear noise "emememme"  coming from (catalytic convertor
or transmission). When sound is there, car is slow down QUICKLY (feel like
harsh downshifting) as If I was pressing the brake lightly but I did not .   1 or 2
second late, When sound gone. Car is coasting as the NORMAL,  the car is
slowing down GRADUALLY  (normal)
 

Each time, when coming to stop, the RPM needle jump one time then
decrease to normal idle speed. 

 
Only happen one time. 

when my car is running on the downhill(really sharpe). Again I let off the  gas
and let the car coast. The rev is stuck in 2000 RPM(gear is stuck??). The brake
is stick. At that time, there is sound like emememememem!!!!. I have to hit the
accelerator again. rev goes up. Then I hit the brake ,  my car slow down and
the rev goes down. 

 

 
the second problme is my car is hard to acceelrate (not noticeable problem)
When engine is cold, when i drive my car out of garage, I hit the accelerator, it
is easy to accelerate and get about 4000 rpm. But right now, it is hard to go
over 3000 rpm.

1 Answer

Did you scan your car for the trouble codes? It would be very hard to diagnose the problem without it.

Your Answer:

CarGurus Experts

  • #1
    tenspeed
    Reputation
    30
  • #2
    Peter Pulone
    Reputation
    20
  • #2
    Teddy Bayr
    Reputation
    20
View All

Find great deals from top-rated dealers

Search

Related Models For Sale

Used Audi S4
10 Great Deals out of 82 listings starting at $12,995
Used BMW 3 Series
66 Great Deals out of 1,175 listings starting at $1,995
Used Audi S6
23 listings starting at $22,990
Used Audi A5
6 Great Deals out of 184 listings starting at $6,977
Used BMW M3
9 Great Deals out of 90 listings starting at $15,995
Used Mercedes-Benz C-Class
107 Great Deals out of 1,440 listings starting at $4,500
Used BMW 5 Series
21 Great Deals out of 329 listings starting at $4,500
Used Chevrolet Corvette
23 Great Deals out of 1,038 listings starting at $14,900

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use. Content will be removed if CarGurus becomes aware that it violates our policies.