• Registered: 2011-08-06
  • Posts: 1

Topic: low idle kills 2.1 litre engine in first minutes of driving

i have a 91 2.1l vanagon.
starts great, holds solid idle at 800rpm
runs problem free after 2 minutes of driving
the exception occurs after starting and when driving for less than a few minutes: as you come to a complete stop the idle quickly plunges to zero, tries to pick up again but then cuts out and the engine dies.
advice please

  • TomB
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  • From: Austin, TX
  • Registered: 2004-03-27
  • Posts: 1,095

Re: low idle kills 2.1 litre engine in first minutes of driving

Several things happen in the transition from cold start to normal running. In the 91 most are keyed off the "Temp Sensor II" that reports engine temperature to the Digifant ECU. This is the blue sensor in the thermostat housing. I've never had one fail, but others report it is common. It is cheap and easy to change. (A clip holds it in place, so you can pull the old and slip in the new one without losing much coolant. Watch out for the oring though...) It might be telling the ECU the engine is warm enough when it isn't.
That's also about the time the Oxygen sensor becomes active. The 91 uses a heated sensor, and perhaps if the heater element or power to it is bad it may not be warmed up enough at that time. The green single wire is the signal from the sensor, and the dual connector is the heater circuit. Should be easy to probe the "body" side of the harness and see if it is supplying 12V to the heater circuit, and check the heater resistance also.
Besides my 91, I also have a 2001 EV, which shows a similar brief stumble during warm-up. Lots more possible causes on that system though, so I'm still working through it.