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Car Forum / Volkswagen / Water Cooled Volkswagen Cars / March 2008VR6 Hot Start Problem
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 (<0.8) as the revs drop indicating the mixture is too lean, which would account for the near stall. Also shows that when the revs shoot up it's opening the injectors for much longer than normal (some sort of last ditch attempt to stop the engine stalling I guess) so it seems to be a fuel problem. Fuel pressure has been checked and seems to be pretty much OK (3.3 Bar or so) so I'm a bit at a loss to see why it's doing this. If it was an air leak somewhere (intake ducting or between manifold and cat) or some other mechanical problem I'd have thought it would be there all the time not just for a minute or so when the engine is hot. Anyone had the same problem and know what the answer may be ??? Al H Have you had the injectors cleaned and tested at RC Engineering? Never mind as you are over in the UK. >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 [quoted text clipped - 15 lines] > >Al H Could be a throttle body or coolant temp sensor issue. > Corrado VR6 has recently starting stumbling badly after a hot start. > Starts [quoted text clipped - 23 lines] > > Al H 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? > Could be a throttle body or coolant temp sensor issue. > [quoted text clipped - 30 lines] >> >> Al H 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 ! > Yeah I was thinking throttle body or CTS too. Can it be cleaned and a > throttle body adaptation done to it? [quoted text clipped - 44 lines] >>> >>> Al H |
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