VR6 Hot Start Problem

- A
- Alex Hopwood
  
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posted
16 years ago

Fri, Mar 21, 2008 10:30 AM

Corrado VR6 has recently starting stumbling badly after a hot start. Starts OK but then the idle speed drops until it almost stalls at which point something kicks in and the revs shoot up after which they start to die again. This repeats maybe 3 - 4 times until all of a sudden the revs shoot up and come back down to a normal idle after which everything is fine. If you try and use throttle to get the revs up it doesn't work, just stubbles even more so it isn't the idle valve. VagCom does show Lambda dropping below

1 and going out of limits (

- J
- Jim Behning
  
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posted
16 years ago

Sat, Mar 22, 2008 4:24 AM

- Z
- zc
  
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posted
16 years ago

Mon, Mar 24, 2008 12:29 AM

Could be a throttle body or coolant temp sensor issue.

- D
- dave AKA vwdoc1
  
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posted
16 years ago

Mon, Mar 24, 2008 4:41 AM

Yeah I was thinking throttle body or CTS too. Can it be cleaned and a throttle body adaptation done to it? Can any codes (DTCs) be pulled from the computer?

Or a residual fuel pressure problem maybe? Fuel pressure either drops down too far or vaporises. Engine running warmer than usual?

Coolant Temperature Sensor is cheap and easy to check or change.

How is it when you shut off the hot engine and then restart it after 5-10 seconds?

- A
- Alex Hopwood
  
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posted
16 years ago

Mon, Mar 24, 2008 3:37 PM

Takes about 10-15 mins before it starts acting up, OK up to then (sometimes it doesn't happened at all). I think it might be a residual fuel pressure problem causing vapour lock. Found something on the net about this by the VagCom guy. Sounded just like my problem. Haven't got around to checking the pressure again yet although I'm sure last time it seemed to do some odd things, went down as per normal (within limits) but then seemed to go up again. Need to check it again and stand there and watch exactly what it does. Forgot to mention it's a 1995 Corrado so no throttle adaptation. Only DTC was Lambda control limit exceeded, but I could see that when I logged lambda as the problem happened (Lambda dropped to < 0.8). Also the coolant temperature seemed fine, smooth change and realistic values so don't think it's that. Will check fuel pressure again when the UK weather brightens up a bit !