Author Topic: Horrible Mileage.....Please Help (Read 3408 times)

Doakster · « **on:** March 22, 2009, 06:32:29 am »

I hadn't driven my 1.6TD in a while over the course of the winter. About half way through I started regularly diving it again. Come to find out I'm only getting 30mpg compared to when I first got the car I was consistently getting 43mpg. I'm stumped as to why. I wouldn't think winter fuel would cause that much of a drop.

Over the summer I replaced the timing belt and everything was good to go, 43mpg. Verified pump timing as well.

I have noticed an excessive amount of oil on the inlet side of my turbo, I've tightened all the oil lines, only thing I can think of is my oil seal in gone in the turbo and reducing boost. I used to be able to hear the turbo spool, now there is no way I can here it.

burn_your_money · « **Reply #1 on:** March 22, 2009, 07:24:57 am »

You should get a boost gauge hooked up to check on the turbo.
How old are the injectors? They could be acting up from sitting

Golf/Jetta · « **Reply #2 on:** March 22, 2009, 11:11:53 am »

as the secound post said with the boost guage and injectors

still using your old fuel (summer fuel)? (varnish screwed it up)
(buy a fuel filter) ASAP (have tools on hand to change it)

if so try using conditioner/diesel purge or alot of ATF + try and get your tank as low as possible with running out. or empty tank and fill with fresh fuel take her for a good spin around town/to work and back.. (use that old filter as much as possible)

bring the new fuel filter and ATF or pre-ATF the filter
fill her up with fresh fuel. run for 5 min and replace filter..

a car sitting around for a season, the fuel just sucks and varnish's.
check to see if there little bubble's in your clear fuel line caused by a vacumm. or your fuel line might have to get replaced (little cracks at the tips | big bubble's)
it will get better and better with every run with fresh fuel

Doakster · « **Reply #3 on:** March 22, 2009, 03:27:51 pm »

I guess I need to clarify, the vehicle was run during the early part of the winter, it was pretty much daily driven about 1-2 miles per day back to work(but not by me, by another family member) about half way through the winter is when I started driving it and consistently saw 30mpg. Truthfully I'm not ok with 30mpg, when I consistently got 43mpg last summer/fall.

I am going to speculate that these injectors are the originals, I can tell the car wasn't cared for like I would have. Car has 109,000 on it now so I bet the injectors do to, it was my intent to have the injectors rebuilt anyway at some point in the future.

As far as the fuel filter, what is the normal change interval? I bought the car with 103,000 on it have put 6k on it with the same filter, I believe the previous owner did change the filter, but again I can't verify it.

I've also run at least 10 tanks of fresh fuel through it, since I started driving it again. Another thing I did was put a little 2-stroke oil in it, but I noticed the bad mileage before I put any 2-stroke oil in with the fuel.

Dakotakid · « **Reply #4 on:** March 22, 2009, 03:37:14 pm »

As a little side note here...are you aware that these Mk. II odometers tend to self-destruct?? I have had cars that count mileage too fast (high)....I have had Mk. II's that intermittently work (counting too few). And, I have Mk. II's that don't essentially have odometers due to the failing little gears.

So, have you double-checked to see how your odometer is working?

jtanguay · « **Reply #5 on:** March 22, 2009, 03:42:43 pm »

as the oil gets dirtier the more soot in it actually increases the abrasiveness, and then the friction losses increase dramatically. i think most people here will agree with me that less soot in the oil means better performance. at least on the butt dyno anyways :lol: but that should only account to a few mpg's...

what you're seeing is probably the winter fuel mix mileage drop. the problem with the old IDI's is that they don't automatically compensate for things such as fuel temperature and intake air temperature, etc. because of this they tend to run good in 'good' weather :lol: meaning not too hot, and not too cold. i think 15C is probably the better temp. all this can account for 5 or more mpg's lost.

other things such as bad/low/old transmission oil can account for a few mpg's as well. wheel bearings if bad enough can account for some mpg losses as well... dragging brakes too. extra weight in the car. (no dead bodies in the trunk right? :lol:) oh and don't forget the air filter!!!

now for the injection pump... you would need to hook up the internal pressure gauge to see what the pump is at and if it needs to be calibrated. apparently this can cause some drastic mpg losses if its out of whack. if there is a lot of vacuum (the pump has to suck harder) on the fuel lines, then that could affect internal pressure as well. common cause is the fuel filter, but also the pickup screen in the tank (if your car has one) could be the culprit.

i think thats most of it covered...

Doakster · « **Reply #6 on:** March 22, 2009, 03:43:48 pm »

Quote from: "Dakotakid"

As a little side note here...are you aware that these Mk. II odometers tend to self-destruct?? I have had cars that count mileage too fast (high)....I have had Mk. II's that intermittently work (counting too few). And, I have Mk. II's that don't essentially have odometers due to the failing little gears.

So, have you double-checked to see how your odometer is working?

Well I can say that I had a GPS in the car awhile back and the OD was only off by 1 maybe 2 mph at most, I would speculate it's due to my tire size, but again I got 43mpg with stock size tires and my 16in rubber.

Doakster · « **Reply #7 on:** March 22, 2009, 03:49:40 pm »

Quote from: "jtanguay"

now for the injection pump... you would need to hook up the internal pressure gauge to see what the pump is at and if it needs to be calibrated. apparently this can cause some drastic mpg losses if its out of whack. if there is a lot of vacuum (the pump has to suck harder) on the fuel lines, then that could affect internal pressure as well. common cause is the fuel filter, but also the pickup screen in the tank (if your car has one) could be the culprit.

i think thats most of it covered...

Where can I get such a gauge?

I also hope that it's mainly due to winter fuel, but I wouldn't think 13mpg would be the result of just winter fuel maybe I'm wrong. Also I completely went through the front end last summer, wheel bearings only have 6k on them, I should change the trans oil because I don't know when that was changed last, and it looks like I should get on changing that fuel filter at least.

Anyone know the service interval of the filter?

Doakster · « **Reply #8 on:** March 22, 2009, 03:51:35 pm »

Quote from: "NoSurrenderAG"

Quote from: "jtanguay"
as the oil gets dirtier the more soot in it actually increases the abrasiveness, and then the friction losses increase dramatically. i think most people here will agree with me that less soot in the oil means better performance. at least on the butt dyno anyways :lol: but that should only account to a few mpg's...

wow that is definitely, definitely true

Just changed the oil/filter about 500 miles ago.....before 30mpg, after 30mpg. Changed it at 5000miles on the oil.

theman53 · « **Reply #9 on:** March 22, 2009, 04:11:05 pm »

The flat red rabbit did that almost exactly when it went to winter diesel. I usually changed the oil at 3,000 too. I bet it will come up soon with the summer mix. Here is a thread for internal pump pressure from another forum.
http://www.vwdieselparts.com/forum/viewtopic.php?t=5936&sid=4cdedce621f8949049c249f58d83c028

Enjoy

hamradio · « **Reply #10 on:** March 22, 2009, 06:00:20 pm »

My car used to get what I believed to be terrible mileage, as the odo was intermittent. :lol:

Doakster · « **Reply #11 on:** March 22, 2009, 06:59:33 pm »

Quote from: "theman53"

The flat red rabbit did that almost exactly when it went to winter diesel. I usually changed the oil at 3,000 too. I bet it will come up soon with the summer mix. Here is a thread for internal pump pressure from another forum.
http://www.vwdieselparts.com/forum/viewtopic.php?t=5936&sid=4cdedce621f8949049c249f58d83c028

Enjoy

Well I'm hoping it's just the winter fuel, but can't hurt to change the fuel filter and see what happens.

Doakster · « **Reply #12 on:** March 22, 2009, 07:02:53 pm »

Quote from: "hamradio"

My car used to get what I believed to be terrible mileage, as the odo was intermittent. :lol:

My speedo has never been intermittent, and I just got done a highway trip where tried to verify the speedo again.

I watched the tenth mile indicator on the trip meter. When I passed a mile marker on the highway I noted what tenth of a mile I was at, when the next mile marker came up it was nearly dead on the original tenth of a mile that I first noted. So I've ruled out the speedo as the problem.

theman53 · « **Reply #13 on:** March 22, 2009, 07:09:38 pm »

I also forgot that when I replaced my injectors things got tremendously better in the MPG department. If it has been 50-100 thousand miles you might try that too if the diesel, oil, and filters change doesn't help. Injectors do wear out over time and I think that the bentley says replace them in the range above.

ObscuredByClouds · « **Reply #14 on:** March 24, 2009, 11:18:26 am »

I got new nozzles but not injectors.. is that good enough?