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Discussion Starter #1
Hello all, and thanks for the great forum.

I have a 2005 auto BEW jetta wagon and the fuel mileage has dropped considerably in the last year. We have replaced the camshaft, lift pump and I have checked and re-checked the timing, but the fuel mileage (Pen and Paper) has dropped from the mid to low forties to around 31 mpg. The only clue I have is that the engine seems to surge at high rpm, like the engine is missing or the air charge is leaking out, but the hoses are all fine to the air inlet. I have checked the operation of the turbo and it is recieving vacuum and making a full sweep of the vanes. Could a plugged intake cause these problems? Could injector adjustment cause these issues? Weak valve springs? MAF? I have a Vag Com and I do all my own work. We have a friend with an 04' that has experienced the same problem. Any input or personal experiences would be appreciated.
 

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Discussion Starter #4
Thanks for the responses.

Haven't logged the maf, but the full throttle test shows 800+, torque value at +1, no error codes. I am going to check the rear brakes tomorrow, but the car seems to roll fine.
 

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Have you ruled out poor fuel? Are you getting your fuel from the same location as last year? What color is your exhaust? If black, then you have rich/unburned fuel. Gas stations are up to no good selling us poor quality fuel, low in cetane and perhaps mixed with water or just tampering with the pump meter. Is there any place to have your fuel checked? I take it that your MPG drop occurred before changing the camshaft? Good luck with your troubleshooting.

bigochief
 

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Graph your coolant temperature and MAF against the RPM and make sure they're ok. The TDI will operate most efficiently when the ECU reads 88degrees C on the coolant temperature.
 
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