I recently purchased a 2003 Jetta TDI at 225k miles (5spd manual). The engine seemed to be in great shape at purchase (no smoke, no funny noises, good power), and the service records were good. I got this car so that I could run something on B100, which I've been doing for ~ 400 miles.
In my last few tanks, I've been tracking fuel economy by taking number of miles driven over the amount pumped into the tank until the pump stops on its own (not worrying about foam or venting). I've gotten 31 and 32 mpg for the last two partial tanks, mainly city driving. This mileage includes pre/post EGR/intake manifold cleaning (it was about 60% occluded - I noticed much better power, but it seems mileage didn't change much). Tires were at 35PSI.
I understand that B100 + city driving will result in lower fuel economy, but it still seems too low for me - I get pretty good mileage on other vehicles and have experience with how to drive turbocharged engines. I picked up VCDS, and the IQ/timing are within spec at idle. The timing is slightly advanced, and the IQ is around 4-5 mg/str, with fairly equal numbers across the different injectors. The turbo doesn't seem to be acting strangely, but I don't really have a good baseline for what it should be like. I tested the MAF by unplugging it, but the car drove like crap after I did that. I'm waiting until I hit 1000 miles on B100 to change the fuel filter.
I decided to do some of the VCDS tests given at: http://ift.tt/2uWxRip, which is to check the injection quantity, boost, and air flow at the MAF.
Under load (3rd gear, moving from 1500-4000 RPM over ~ 17 seconds without flooring it), all of these figures seem low to me, compared with the reference values given at the site. I'm not clear whether these values are within spec, or whether they are related to my fuel economy issues.
(click on images for full size)
Injection quantity:
Boost pressure:
Air mass (I think the "Actual" mass drops off at the end because I wasn't really pushing it at the upper RPMs):
Should I be looking further into why values in all of these plots seem low, or did I bungle the test? Are these related to the low fuel economy.
In my last few tanks, I've been tracking fuel economy by taking number of miles driven over the amount pumped into the tank until the pump stops on its own (not worrying about foam or venting). I've gotten 31 and 32 mpg for the last two partial tanks, mainly city driving. This mileage includes pre/post EGR/intake manifold cleaning (it was about 60% occluded - I noticed much better power, but it seems mileage didn't change much). Tires were at 35PSI.
I understand that B100 + city driving will result in lower fuel economy, but it still seems too low for me - I get pretty good mileage on other vehicles and have experience with how to drive turbocharged engines. I picked up VCDS, and the IQ/timing are within spec at idle. The timing is slightly advanced, and the IQ is around 4-5 mg/str, with fairly equal numbers across the different injectors. The turbo doesn't seem to be acting strangely, but I don't really have a good baseline for what it should be like. I tested the MAF by unplugging it, but the car drove like crap after I did that. I'm waiting until I hit 1000 miles on B100 to change the fuel filter.
I decided to do some of the VCDS tests given at: http://ift.tt/2uWxRip, which is to check the injection quantity, boost, and air flow at the MAF.
Under load (3rd gear, moving from 1500-4000 RPM over ~ 17 seconds without flooring it), all of these figures seem low to me, compared with the reference values given at the site. I'm not clear whether these values are within spec, or whether they are related to my fuel economy issues.
(click on images for full size)
Injection quantity:
Boost pressure:
Air mass (I think the "Actual" mass drops off at the end because I wasn't really pushing it at the upper RPMs):
Should I be looking further into why values in all of these plots seem low, or did I bungle the test? Are these related to the low fuel economy.
Can you help troubleshoot low mileage (ALH 2003 Jetta)
