Question about 1997 Volkswagen Jetta
I suspect you need a new thermostat. It should be running at 195 degrees F.
If the engine does not fully warm up, the engine can not go into emission control mode.
The engine temperature sensor sends a signal to the engine/emissions computer that the engine is now at normal operating temp. The computer then starts controlling fuel flow, EGR, etc. so that emissions are being controlled.
When the enigne is cold, you are in what we call "open loop" meaning no emission control.
Get the thermostat installed first. Make sure it's the same temp rating as the one that's in there. Either 180 degrees or 195 degrees.
Then you should pass.
Posted on Mar 03, 2009
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Posted on Jan 02, 2017
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