I have a 2004 diesel bug. After it warms up the rpms surge from 2000 to 2500 or 2800 rpms and the car sorta bucks along until you step on the pedal to go faster.I had a mechanic look at it and he said that nothing shows up on the diagnostic scan.please oh please help. Thanks.
The issue may be the EGR valve. Sometimes the valve can test out OK with a vacuum pump but can still cause issues with surging. Is this happening between a quarter and half throttle? The reason you wont notice it before it warms up is because the ECM doesnt activate the EGR valve when it is cold. One temporary test you could do is unplug the EGR valve and try and drive the car once it is warmed up. If this stops the surging this is the issue. One other issue could be your Fuel pressure regulator. Your fuel pressure could be low from this and it will cause your fuel injectors not to be able to vaporizefuel as much causing the bucking feeling. Keep me posted. If you found this solution helpful please rate it when you get a chance.
Thanks - Tech101
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throttle pos. sensor.
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