Alignment can't be far off, tracks straight and doesn't chew rubber, same fuel as IBW, he lives few towns over and gets at least 10 better MPG,
We had our mk4 for about 7 years and never got that bad mileage. Best was 4,7l/100km and worst probably around 5,7, I think that's in the 40-50mpg range. Always filled to the brim and calculated like @AndyBees.
Your mileage sure is too low, highway mileage should not be different with or without injectors/tune since you're not requesting more power than it takes to do 75mph. Other than timing being very retarded (causing smoke and bad mpg) there is not much more to check engine wise. you'd almost need a fuel leak to get that bad mpg doing 75mph.
Bob, same here! I gave my son the 2000 Jetta and he don't drive it much because shortly thereafter he purchased an 04 with the BEW dirt cheap and low miles. Also, I purchased my brothers 03 with an 01 engine ............. I don't drive it much and I've not driven my 84 Vanagon with the 02 ALH in months .... Being honest and revealing, a little over a year ago, I purchased a very low miles 11 Tiguan with one of VWs biggest engineering goofs, the 2.0 TSI engine...... fuel economy sucks and it has a lot of potential issues of which some are beginning to show their ugly faces. But, the darn thing is awesome to drive.......... from about 2000 RPMs out to 5000 RPMs, it has 200 HP and 200 Ft lbs of torque ........flat on the graph! The 6-speed DSG is awesome!
Random thoughts:
Didn't check pump number but I have all the service records since the car was new, didn't see anything about pump, but I will check. I did see bubbles but didn't think much of it, will check if still there. Sometimes it smokes at 1/2 throttle when I accelerate, not always.
These can be related: Consider the pump is ingesting air limiting the amount of fuel injected, ecu compensates by swinging QA, but the air is not constant: it varies. Going from large amounts of air to suddenly very little will result in ecu over-compensation and over-fueling until QA can adjust again.
What causes air ingestion? How did you address that?
I got this nailed down: fill up till I see fuel in the neck, wait for the foam to break down and I see clear fuel, go to the same pump, park in the same spot so if the car is slightly pitching up/down it's consistent.
In my case, it was bad fuel hoses/lines, bad thermo-t, tired spring Clamps, partially clogged fuel filter (mild fuel gelling during recent arctic temps), and a plugged/restricted fuel sender pickup.
Some tdi’s just get bad mileage, it’s something we can’t figure out just yet. I’ve always averaged around 45mpg city and usually 53-55 highway. 18” OEM wheels 225/40. I believe coolant temperature and tune plays a huge role in fuel economy. Just like IBW 700 tanks are normal. My best tank was 982 miles I think, heading to Miami with the wife before fuel light came on.
Slipping clutch = I dive like a granny = better MPG.Hang on a sec.... so you're driving around with a slipping clutch, dirty and\or malfunctioning MAF and can't figure out why your MPG is suffering?
Could it possibly be impacted by the loss of power transfer and\or the inability to properly read airflow in order to supply the correct amount of fuel?
PP520 installed by Kraftwereke, tried various IQ adjustment settings from 3 to 8
I get light boost at idle, maybe 1/2 psi, checked the actuator with vacuum pump, it's in spec, still made an adjustment 1 turn to lengthen the rod, then went back to stock after few tanks, no change
