Here’s one for you all-
For the last year or so I’ve been trying to figure out why my mileage is
down around 25 per gallon city / 29 highway. I put in a TT exhaust 6 months
back which may have helped a little but not much. New O2 sensor made no
difference. New rotor and Dist cap, plugs, ditto. Summer and winter same
mileage, running with AC or without makes a slight difference but not a lot.
No vacuum leaks found. I was wondering if perhaps I had a leaky injector and
had put this on my to do list when I just took the car on an extended run
from central Texas up to Colorado. Lots of highway miles.
As I drove up the mileage began to improve with each tank. Around 30 mpg
around Lubbock, 32 at Colorodo Springs. One week of driving around the
state, a couple of days in the city and then 4 or 5 in the high country over
mountain passes. By the end of the week my mileage on one tank (90 octane –
couldn’t find higher) was at 37.6 mpg. I wondered if maybe the hard running
had made something settle out and my mileage would stay up in the mid 30s
highway.
Wrong. As I drove down through New Mexico fuel economy began to fall – first
down to 31 mpg, and then across west Texas back down around 29 on the
highway.
Does anybody have an explanation for why this is happening? Otherwise the
car runs fine, though it seems to prefer the cooler winter weather (‘course,
I do to, so this may be my imagination). The only constant seems to be lower
elevation means poorer mileage. Any thoughts?
TIA,
Chris
would different gas hurt the mileage some?
maybe FI coolant temperature sensor faulty?
bad ground wires at cyl. head or intake manifold?
bad air flow box?
bad/clogged cat. conv.?
just some thoughts :-)
later,
dave
Reminder……..
Before you criticize someone, you should walk a mile in their shoes. That way,
when you criticize them, you are a mile away from them, and you have their
shoes. Frieda Norris
"starburst" <chi…@nospam.mail.utexas.edu> wrote in message
news:bgq0rv$oeo$1@geraldo.cc.utexas.edu…
> For the last year or so I’ve been trying to figure out why my mileage is
> down around 25 per gallon city / 29 highway.
That’s typical for my GTI in my usual commute.
"dave" <vwd…@aol.comANTISPAM> wrote in message
news:20030806082155.28299.00000984@mb-m24.aol.com…
> would different gas hurt the mileage some?
Maybe (oxygenated winterized gas usually hurts mileage in my experience) but
I think we’ve ruled that out here from his information.
> maybe FI coolant temperature sensor faulty?
Could be. Is the idle normal or is it a little fast, esp. when warm? If
fast, that could be it.
> bad ground wires at cyl. head or intake manifold?
> bad air flow box?
> bad/clogged cat. conv.?
all worth checking. also check the air filter.
I’d also check timing. Shouldn’t need the 90 octane fuel (87 should be fine
for a 1.8L 8V A2).
> would different gas hurt the mileage some?
I thought this at first, because I put a tank of shell in on the way,
instead of my normal Chevron. But I had several different types of fuel over
the trip, and they seemed to make no difference on mileage. Elevation seemed
to matter – that’s what’s so funny.
> maybe FI coolant temperature sensor faulty?
new last year, and otherwise the car works fine. A temp sensor would be
faulty all of the time, wouldn’t it?
> bad ground wires at cyl. head or intake manifold?
All recently cleaned with contact cleaner. And again, why the change when I
took the car up high?
> bad air flow box?
Maybe. Hmmm. How would I check this?
> bad/clogged cat. conv.?
It’s not rattling or anything and I don’t have any other symptoms.
> Reminder……..
> Before you criticize someone, you should walk a mile in their shoes. That
way,
> when you criticize them, you are a mile away from them, and you have their
> shoes. Frieda Norris
Love this tag line, btw. Thanks for the ideas – Chris
> > For the last year or so I’ve been trying to figure out why my mileage is
> > down around 25 per gallon city / 29 highway.
> That’s typical for my GTI in my usual commute.
Maybe we should all move to Colorado to save gas and help win the war on
terrorism!
;-]
Chris
"Matt B." <no…@hellno.com> wrote in message
news:%K8Ya.9255$Ye.8897@fed1read02…
> "dave" <vwd…@aol.comANTISPAM> wrote in message
> news:20030806082155.28299.00000984@mb-m24.aol.com…
> > would different gas hurt the mileage some?
> Maybe (oxygenated winterized gas usually hurts mileage in my experience)
but
> I think we’ve ruled that out here from his information.
> > maybe FI coolant temperature sensor faulty?
> Could be. Is the idle normal or is it a little fast, esp. when warm? If
> fast, that could be it.
No. It’s a little slow, in fact, which I think is being caused by a sluggish
idle valve, but I’m not sure.
> > bad ground wires at cyl. head or intake manifold?
> > bad air flow box?
> > bad/clogged cat. conv.?
> all worth checking. also check the air filter.
The filter is about 2 years old and isn’t in bad shape (I can still see
light through it).
> I’d also check timing. Shouldn’t need the 90 octane fuel (87 should be
fine
> for a 1.8L 8V A2).
If I don’t run premium through it it pings like hell, especially in the
summer, and my mileage goes down a bit. It’s real hot here. The timing is
right, too.
I don’t know what to think, other than the car just doesn’t like Texas.
Chris
I thought I was the only one… I have a ’91 Jetta w/ digifant2 and that’s
almost exactly the experience I have. Most times I get around 30ish,
occasionally I’ll get really really good mileage and a few times a little
worse. I’ve checked all the things suggested and then some. Maybe this is
just typical mileage for a digifant2 engine?
Let me know if you’re onto something with the injector idea… that’s
something I haven’t actually looked into yet.
-Dave
"starburst" <chi…@nospam.mail.utexas.edu> wrote in message
news:bgq0rv$oeo$1@geraldo.cc.utexas.edu…
- Hide quoted text — Show quoted text -
> Here’s one for you all-
> For the last year or so I’ve been trying to figure out why my mileage is
> down around 25 per gallon city / 29 highway. I put in a TT exhaust 6
months
> back which may have helped a little but not much. New O2 sensor made no
> difference. New rotor and Dist cap, plugs, ditto. Summer and winter same
> mileage, running with AC or without makes a slight difference but not a
lot.
> No vacuum leaks found. I was wondering if perhaps I had a leaky injector
and
> had put this on my to do list when I just took the car on an extended run
> from central Texas up to Colorado. Lots of highway miles.
> As I drove up the mileage began to improve with each tank. Around 30 mpg
> around Lubbock, 32 at Colorodo Springs. One week of driving around the
> state, a couple of days in the city and then 4 or 5 in the high country
over
> mountain passes. By the end of the week my mileage on one tank (90
octane –
> couldn’t find higher) was at 37.6 mpg. I wondered if maybe the hard
running
> had made something settle out and my mileage would stay up in the mid 30s
> highway.
> Wrong. As I drove down through New Mexico fuel economy began to fall –
first
> down to 31 mpg, and then across west Texas back down around 29 on the
> highway.
> Does anybody have an explanation for why this is happening? Otherwise the
> car runs fine, though it seems to prefer the cooler winter weather
(‘course,
> I do to, so this may be my imagination). The only constant seems to be
lower
> elevation means poorer mileage. Any thoughts?
> TIA,
> Chris
Dave said>
>I’ve checked all the things suggested and then some. Maybe this is
> just typical mileage for a digifant2 engine?
I don’t know. But did you see the posts today from those folks up in Canada
averaging 35+ per gallon on highway trips? Man.
> Let me know if you’re onto something with the injector idea… that’s
> something I haven’t actually looked into yet.
A local mechanic suggested it. He advised to remove the plugs and jumper the
fuel pump relay and then look to see if fuel was dripping into the
cylinders. I haven’t tried it yet, but I might sometime soon. If you try it
let me know what you find, OK? Still, it seems a long shot to account for
such low miles, and it doesn’t explain why mileage goes up so much
sometimes.
Shrug.
Chris
87 is fine for my 91 Golf… but it does run a little nicer on premium fuel.
Gets slightly better mileage, but I don’t think it is worth the price
difference… of course when gas comes down cheap, I get it for it…. If I
feel inclined.
PS – don’t tell me that the premium does nothing for an engine that doesn’t
require it, I have heard all that, and don’t believe it… If I can feel
slight improvements, even if they are in my mind, tis better.
"Matt B." <no…@hellno.com> wrote in message
news:%K8Ya.9255$Ye.8897@fed1read02…
- Hide quoted text — Show quoted text -
> "dave" <vwd…@aol.comANTISPAM> wrote in message
> news:20030806082155.28299.00000984@mb-m24.aol.com…
> > would different gas hurt the mileage some?
> Maybe (oxygenated winterized gas usually hurts mileage in my experience)
but
> I think we’ve ruled that out here from his information.
> > maybe FI coolant temperature sensor faulty?
> Could be. Is the idle normal or is it a little fast, esp. when warm? If
> fast, that could be it.
> > bad ground wires at cyl. head or intake manifold?
> > bad air flow box?
> > bad/clogged cat. conv.?
> all worth checking. also check the air filter.
> I’d also check timing. Shouldn’t need the 90 octane fuel (87 should be
fine
> for a 1.8L 8V A2).
I have seen bad fuel pressure regulators that even dump fuel through the vacuum
hose.
I have seen the flaps get stuck in the air flow box.
throttle switches or throttle linkage either bad or sticking.
I believe you said it was pinging, maybe your knock sensor is malfunctioning.
How did you check the ignition timing and advance?
brakes dragging, or wheel bearings bad?
did you check all of the wiring and components from the ECU plug?
just some thoughts!
later,
dave
Reminder……..
Before you criticize someone, you should walk a mile in their shoes. That way,
when you criticize them, you are a mile away from them, and you have their
shoes. Frieda Norris
"starburst" <chi…@nospam.mail.utexas.edu> wrote in message
news:bgrc5e$flo$1@geraldo.cc.utexas.edu…
> If I don’t run premium through it it pings like hell, especially in the
> summer, and my mileage goes down a bit. It’s real hot here. The timing is
> right, too.
FWIW, my GTI very rarely pings even when hot. Right now I have a mild
heating issue becuase the fans aren’t coming on when they should, so my
temperature in stop-go traffic gets up there pretty high. However even when
high temperature and I shift kinda early (under 2000) rpm, mine rarely pings
at all even on 87. I also noticed that when I switched to Bosch Platinum
2-electrode plugs that it made a noticeable difference in mileage. Might
want to try those. Not the 4-electrode though…I’ve run those before and
didn’t notice any big differences…but for some reason the 2-electrode ones
do very well.
-Matt
> I have seen bad fuel pressure regulators that even dump fuel through the
vacuum
> hose.
Interesting… I’ve wondered about this and will check..
> I have seen the flaps get stuck in the air flow box.
> throttle switches or throttle linkage either bad or sticking.
I think these are all ok. The flaps move smoothly. But maybe the air flow
sensor? I don’t know enough about how it works to make an informed guess,
but the resistance works per bentley.
> I believe you said it was pinging, maybe your knock sensor is
malfunctioning.
> How did you check the ignition timing and advance?
This also is a good thought. I noticed that the engine started pinging far
more down here than in Colorado, where I bought the car, and wondered if the
knock sensor might be the culprit.
> brakes dragging, or wheel bearings bad?
Don’t think it’s the bearings, but maybe the brakes are funky. I’ll have to
think about how to check this.
> did you check all of the wiring and components from the ECU plug?
No, but I’ll put it on the long-term to do list.
Thanks for the ideas – Chris
It’s Texas…simply put. I drove an 85 Toyota van all over Nth America a few
years back, top to bottom, side to side. The only place I had a problem with
it was in Texas…crossed the border from NM and 30 mins
later…bam…stalled. Ended up being a fuel line heat shield issue, but
this was Jan/Feb…once I got outta there and started heading north again,
all was well.
"starburst" <chi…@nospam.mail.utexas.edu> wrote in message
news:bgs0dp$q3b$1@geraldo.cc.utexas.edu…
- Hide quoted text — Show quoted text -
> Dave said>
> >I’ve checked all the things suggested and then some. Maybe this is
> > just typical mileage for a digifant2 engine?
> I don’t know. But did you see the posts today from those folks up in
Canada
> averaging 35+ per gallon on highway trips? Man.
> > Let me know if you’re onto something with the injector idea… that’s
> > something I haven’t actually looked into yet.
> A local mechanic suggested it. He advised to remove the plugs and jumper
the
> fuel pump relay and then look to see if fuel was dripping into the
> cylinders. I haven’t tried it yet, but I might sometime soon. If you try
it
> let me know what you find, OK? Still, it seems a long shot to account for
> such low miles, and it doesn’t explain why mileage goes up so much
> sometimes.
> Shrug.
> Chris
black francis wrote:
> It’s Texas…simply put. I drove an 85 Toyota van all over Nth America a few
> years back, top to bottom, side to side. The only place I had a problem with
> it was in Texas…crossed the border from NM and 30 mins
> later…bam…stalled. Ended up being a fuel line heat shield issue, but
> this was Jan/Feb…once I got outta there and started heading north again,
> all was well.
I think it’s the altitude (and dry air). I live in Santa Fe, NM, where
I drive a manual 1.8T Jetta. I routinely get 34-35 mpg on the way up to
the high country of Colorado and 37 mpg on the way back. My mpg on my
daily 80 mi RT commute is more perhaps 32-33 mpg. I always use premium
fuel – particularly since the octane is lower in Colorado/New Mexico.
Even in my last car (a 4WD Suzuki Grand Vitara), I sometimes got 27
mpg on the way back from Colorado – versus 22-23 commuting near Santa
Fe. Conversely when I took the Grand Vitara out to California, my
mileage fell to as low as 19-20 mpg. It rose again to 25-27 mpg as I
drove into the Colorado Rockies on the way home.
Just another reason to love the mountains. :)
Judith
Thanks for the post, Judith. You gotta admit that it’s kinda freaky, though.
Back in the old days, I used to see cars from the flatlands trying to chug
up the passes near home, belching out smoke because the carbs were set for
lower elevation. Now, with computer controlled ignition that automatically
compensates, my mileage actually gets better at higher altitude. Wierd.
Wish *I* was in Santa Fe…
C
"Judith Cohn" <jdc…@swcp.com> wrote in message
news:bh7fln$e47$1@iruka.swcp.com…
- Hide quoted text — Show quoted text -
> black francis wrote:
> > It’s Texas…simply put. I drove an 85 Toyota van all over Nth America a
few
> > years back, top to bottom, side to side. The only place I had a problem
with
> > it was in Texas…crossed the border from NM and 30 mins
> > later…bam…stalled. Ended up being a fuel line heat shield issue, but
> > this was Jan/Feb…once I got outta there and started heading north
again,
> > all was well.
> I think it’s the altitude (and dry air). I live in Santa Fe, NM, where
> I drive a manual 1.8T Jetta. I routinely get 34-35 mpg on the way up to
> the high country of Colorado and 37 mpg on the way back. My mpg on my
> daily 80 mi RT commute is more perhaps 32-33 mpg. I always use premium
> fuel – particularly since the octane is lower in Colorado/New Mexico.
> Even in my last car (a 4WD Suzuki Grand Vitara), I sometimes got 27
> mpg on the way back from Colorado – versus 22-23 commuting near Santa
> Fe. Conversely when I took the Grand Vitara out to California, my
> mileage fell to as low as 19-20 mpg. It rose again to 25-27 mpg as I
> drove into the Colorado Rockies on the way home.
> Just another reason to love the mountains. :)
> Judith
Yep a minor adjust is all that’s needed. All kidding aside it could be as
easy as the reverse solenoid is bad on the valve body to a more serious
problem such as a clutch or other mechanical problem A good VW dealer can do
what’s called an AG4 test which checks everything out to determine what’s
faulty. Figure about 4 hours(max) labor for doing the test.
"NPNoonan" <npnoo…@aol.com> wrote in message
news:20030806001209.13468.00000052@mb-m27.aol.com…
- Hide quoted text — Show quoted text -
> Just the other day I went to back out in front of my house and found out
my ’95
> Jetta GLX-VR6 (113k miles) didn’t want to shift into reverse. It’s an
automatic
> transmission and when I shift it, it seems it gets stuck in neutral. I
tried
> transmission fluid conditioner/treatment. That did nothing.
> All of the driving gears work fine. It’s only reverse that I’m having
trouble
> with, which has me thinking (or hoping) that it’s only maybe a minor
adjustment
> on the tranny that may have to be made. If not, I was told I’m looking at
> spending $1,000-$1,500 for another transmission plus the labor fees to
have it
> installed.
> If any one has experienced a similar problem or could offer some advice,
please
> reply.