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Rough idle (high then low RPMs) and surges or lurches when coasting. Hood wont open

Tiny
VR6 DRIVER
  • MEMBER
  • 1995 VOLKSWAGEN GTI
  • 193,000 MILES
My 95 GTI VR6 has about 60k on engine and 193 on tranny/car. It starts up great, but sometimes idles up and down in rpms while sitting still. It drives okay in lower speeds and shifts smoothly, but when I let off gas to coast, it lurches. When I push on the gas or depress the clutch, it goes away. Happens in 1st, 2nd, 3rd. I have only had the car for a few months and dont drive it much, but it didnt do that the first few weeks (it wasnt 90 to 100 degrees then either, in case thats a factor.) Everything else seems to be working fine. My thoughts go to a bad ECM / ECU, a leak in vacuum somewhere, or some Idle control valve, etc. Unfortunately, the hood cable is broken and cant get into engine to take a look.
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Thursday, August 16th, 2012 AT 9:30 PM

8 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Try cleaning the throttle plate on both sides with chokeor fuel injector spray clener. Wipe it all out if you cansee if that helps.
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Thursday, August 16th, 2012 AT 11:00 PM
Tiny
VR6 DRIVER
  • MEMBER
  • 5 POSTS
Thanks, I will try that. Not exactly sure where that is, but can figure it out most likely. I finally got the hood to unlatch. I also found that the hose leading into the air filter box is cracked open. Could this be part of the problem (even though its not cold outside) I will replace it too.
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Saturday, August 18th, 2012 AT 6:03 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The throttle plate is at the end of your air duct going to the motor. Make sure to hook up air duct before starting car.
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Saturday, August 18th, 2012 AT 12:50 PM
Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
'95 Throttle Body should be non-motorized and closes 100% when at
idle (no air past throttle plate).

The Idle Air Valve is used to bypass air around the throttle body
for Idle purposes.

A scan of ECM data via VCDS would be the best way to track down what
is going on (fault codes, fuel trim correction etc).

Thomas
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Saturday, August 18th, 2012 AT 6:33 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
This type of situation won't appear as a fault code because the computer thinks it's working.
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Saturday, August 18th, 2012 AT 11:02 PM
Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
I beg to differ. "Idle Control" faults are common. Idle regulation
faults (Idle to High, Idle too low) will be flagged if there is an
issue.

Even if no code is stored. A scan tool can be of help, by viewing
ECM inputs.

Thomas
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Saturday, August 18th, 2012 AT 11:38 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
True if a pro does this, not your average person that emails in to get some type of answer. Most of the people don't even have a scanner let alone how to u se one.
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Saturday, August 18th, 2012 AT 11:44 PM
Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
I am merely providing info. Just like you with your cleaning of
the throttle.

Thomas
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Saturday, August 18th, 2012 AT 11:51 PM

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