What transmission? How old is your fuel filter?
2003 Jetta TDI with 204k+ miles and recently the mileage has decreased (last 10 fill ups). 5 years ago, I was averaging a consistent 46.2 MPG all the time and now I rarely hit 40MPG anymore. What made me write in is that I just put 600 miles on the car, all highway which normally results in the best mileage I see. Tonight it averaged out to 38.4. Is this just age?
In case it's not age, here's what I've looked at hoping there's some maintenance I've missed
1) The intake is not all coked up with carbon
2) The air filter was just replaced
3) The MAF was out of spec last year and causing the car to go into limp mode. I replaced the MAF last year and recently found it's still within specs
4) Tires are properly inflated
5) I switched diesel stations in case there is a difference in fuel now from a few years ago. I've seen no change in mileage.
6) No engine codes or engine light
7) The timing is within specs
The car can breathe and the fuel was eliminated as a factor, what else could it be? aging injectors?
What transmission? How old is your fuel filter?
A can of diesel purge may help or your injectors could be getting old and tired and the nozzles are worn so you are not getting as efficient of a spray pattern from them any more leading to incomplete burn and reduced fuel economy. If the springs are worn they may be popping at a lower pressure and letting more fuel through at a lower pressure which once again leads to an incomplete burn and reduced fuel economy.
Here is a link with more info on the nozzles and there is a link to a video showing how to do a purge.
Last edited by DanV990; 10-09-2012 at 11:28 PM.
I've looked at upgrading my injectors in the past, but decided to go with a chip a few summers ago. The injectors are still stock and I've never used any additives. I would be interested in replacing the injectors but I would probably go with just stock at this point to return mileage to the old girl.
Last I remember kermatdi.com had good injectors, do you guys have any suggestions on brands? I'm not super interested in spending a bunch of money on a 9+ year old car with 200k+ miles.
If changing the fuel filter this weekend doesn't make a difference, I'll strongly consider a new set of injectors
new injectors; make sure you loosen and tighten towards head, so wrench will be in opposite directions, towards trans when loosening and toward pulleys when tightening.
(w/new injectors)run a can or 2 of lubro-moly straight, make sure you use additive when fueling up.
run the run off return line back into can when flushing with lubro moly.
the "little" D
also 962 -0 to 60 in 4 years-
why??more than 1 wire to shut her off?? a blasphemy!
the smaller nozzle will atomize fuel better, leading to a more efficient burn, and more power/economy..
the smaller nozzle is just no good for performance, because of the limited fuel flow..
but if you are staying stock, then it doesnt matter anyways..
simply changing to bigger injectors will not give you more power or mileage.. you need to have the engine re-tuned before you can see the benefits of either..
Bigger nozzles absolutely increase mileage and power even with stock tuning.. The issue with the stock .184 nozzles in the manual transmission cars is that they are still injecting fuel near the end of the timing window. This doesn't help economy... With bigger nozzles (say .205's) you'll have all your fuel injected well before the window closes.. With just a nozzle upgrade, a manual tranny ALH (Stock) will see a 5% increase in mileage, 10-15hp and 30-40ftlbs of torque..
No need to re-tune in order to see the gains a set of nozzles will give you.
The OP should look into a set of Sprint or PP520's.. Great upgrade for a stock ALH.
I changed my fuel filter and I'm finally writing back in after I've run a full tank of diesel through the car. The mileage is still sitting in the high 30s. As you can guess, I'm disappointed.
If the next best option is to replace the nozzles, I'll try that to get the mileage back. I wandered around kermatdi to find stock ALH nozzles. I already have a chip in the car so I think I'll keep the nozzles stock so I don't have to get my ECU tuned. About the cheapest option I found is $335 going with their sprint 520 nozzles (older model) vs $425 with the new DLC nozzles. Everything I read, save a few articles, says just send the nozzles out for replacement and testing from a place like kermaTdi since I don't have the equipment to perform a "pop" test, etc.
My only concern is could something else be causing this mileage decrease? Perhaps the turbo?
go to IDparts, grab some .216 nozzles, and have them shipped for 299$.
Bad turbo COULD hit mileage, but only if its a pile of **** or its just really blown. Have you been running additive like DK in it?
2) I thought KermaTDI nozzles are an upgrade from stock? Are the sprint 520 nozzles junk?
3) $299 as you suggest is only $36 difference from sending my injectors to KermaTDI, having them replace the current nozzles with Sprint 520s, test them and send them back. I thought testing was important, no?
I've never run an additive in the car. Last I knew it was never required or even suggested.
If your injector bodies have a lot of miles on them, getting them balanced with your new nozzles is a good idea (Seatman is going to scream tears of joy to hear me say this, lol)..
Sprint 520's are great nozzles for an otherwise stock car. PP520's would be another good choice.
Don't worry about your turbo, I don't know why that was even brought up.
How about intake manifold clogging?
For our rotary pump TDI's, I 1,000% recommend an additive like diesel kleen. I notice 2-3mpg improvement when using it. Not to mention, the reassurance of my fuel not gelling in winter time and not worrying about trashing my pump and injectors from lack of lubricity.
This. If anything, it's only a few bucks for these injectors to be balanced... but only very few shops can actually shim them or adjust them. Specifically, Bosch shops.