CAR RUNS FINE WHEN UP TO SPEED ROUGH IDELING ...

  • Tiny
  • Gwendolyn Peden
  • 2004 VOLKSWAGEN PASSAT
  • 150,000 MILES

Car runs fine when up to speed, rough ideling when stopped at stop sign
had a tuneup, new oxygen sensor installed

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Thursday, November 15th, 2012 AT 12:24 AM

9 Replies

  • Tiny
  • Exovcds
  • MEMBER

Tdi or gas engine? What size engine if gas?

Thomas

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Thursday, November 15th, 2012 AT 1:04 AM
  • Tiny
  • Gwendolyn Peden
  • MEMBER

Gas engine 1.8

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Thursday, November 15th, 2012 AT 1:24 AM
  • Tiny
  • Exovcds
  • MEMBER

Vacuum leaks and or a dirty throttle body can cause idle issues.

Having a look at short term and long term fuel trim values with a scan tool can quickly indicate if a vacuum leak is a possibility.

Smoke testing the intake can find leaks that are not visible or audible.

Engine mounts can add to the roughness feel (excessive shaking of the engine), so those should be checked as well.

Thomas

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Thursday, November 15th, 2012 AT 1:32 AM
  • Tiny
  • Gwendolyn Peden
  • MEMBER

Can a dirty throttle be cleaned or do you have to buy a new one another thing car gets a code number of P0507 which states idle control system revolution per minute higher than expected

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Thursday, November 15th, 2012 AT 1:37 AM
  • Tiny
  • Exovcds
  • MEMBER

Throttle bodies can be cleaned and an adaptation performed... sample from a Jetta I cleaned:

http://www.youtube.com/watch?v=OAfeBLENkfA&;feature=plcp

Usually it is a low idle problem.... when the dirt gets too much in the throttle bore.

The high idle could be due to the throttle being faulty or the vacuum leaks I mentioned earlier.

Cleaning and adapting, as well as smoke checking is what I would start with if you came to my shop.

There are smoke testing clips on my site... search for smoke in the search bar to get some sample clips.

Thomas

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Thursday, November 15th, 2012 AT 1:45 AM
  • Tiny
  • Exovcds
  • MEMBER

I forgot to mention "check valves or one way valves" that can also cause idle / performance issues. The 1.8T engine has a number of them.

The check valves allow and block air flow when the engine is under turbo boost or not under boost.

Thomas

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Thursday, November 15th, 2012 AT 1:48 AM
  • Tiny
  • Gwendolyn Peden
  • MEMBER

Thank you for your help I really appreciate it. One other question, if I need a new throttle after being put in does it need to be programmed. I will give my mechanic the info and let him see the video, again thanks for the help. It is so useful.

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Thursday, November 15th, 2012 AT 2:03 AM
  • Tiny
  • Exovcds
  • MEMBER

Sorry about the late reply. I was driving home.

I always perform the adaptation on new throttle bodies. As long as it is the correct one for the engine, it should be ok.

Don't buy any parts until they are confirmed to be bad!

I can only guess over the internet. If your mechanic is not familiar with VWs, check with a VW Specialty shop in your area.

Thomas

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Thursday, November 15th, 2012 AT 2:35 AM
  • Tiny
  • Gwendolyn Peden
  • MEMBER

Thank you very much enjoy the rest of your evening

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Thursday, November 15th, 2012 AT 2:43 AM

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