Very Poor Fuel Economy - page 1 - Troubleshooting - VWDiesel.net The IDI, TDI, and mTDI source.

• Very Poor Fuel Economy by 55mpg06 on 20 Jun, 2007 09:54
• Hello everyone, just a quick question. My newly acquired 1990 jetta TD has about 270’000km on it and has been a source of a few unpleasant surprises already. When I filled up for the couple of times I noticed I barely got 40mpg with mixed city and highway driving (with my NA I got in the 50s easy in town).  
  
  Time for some servicing. I ran Diesel Purge through the system and it quieted up a pinging injector very nicely. I then checked the timing while changing the timing belt and found it to be a little high and knocked it down to spec of 1.00mm (until everything is figured out). I switched to semi-sythetic 15-40 oil (love the stuff) after a engine flush treatment. I flushed out the cooling system very well and replaced thermostat. I checked and greased the wheel bearings as needed while I replaced the brake pads, shoes, and drums. Finally I took the car in for a 4 wheel alignment. I was very surprised over the next few fill-ups (yes I use additive) that I now get 35mpg tops including on a trip to Vancouver- less than before!  :shock:
  
  I checked the smoke screw and its factory paint has never been touched. I also have been told that when I shift while driving there is a rich, dark, very black bellow of smoke out the exhaust. I am not losing any oil, or antifreeze, have plenty of power (like other TDs I drove) and the Injection pump is not leaking.
  
   The injectors seem quiet now, but could one still be faulty? The previous owner said he did have starting problems but the Plurge seemed to clear it up Or since I haven’t read up too much on the Turbo yet  :oops:  is there a setting the previous owner changed on it (he wasn’t mechanically inclined too much and a shop did the head gasket 4 years ago.
• #1 by Doug on 20 Jun, 2007 10:33
• Is the engine running hot enough? Where does the temperature guage sit? Does the cooling system pressurise?
  Have you checked the compression?
  Is there any blockage to the intake system like a rag or mouse nest on the air filter?
  Do you have a leak on the return line to the fuel tank? Or is your water trap leaking?
  What fuel are you using?
• #2 by 55mpg06 on 20 Jun, 2007 10:57
• Thanks Doug for the relpy. The temp gage sits just a hair above 1/2 (on the warm side) in 25oC weather. I havent checked the compression with a gage yet, but when hand cranking the engine it seemed good and I have plenty of power. Car was loaded with 3 adults and their stuff on way to Vancouver and went up hills plenty fast enough for me... at this time :wink: .
  
  The air intake seemed O.K. when I had the pipes apart to change the belt but I havent put my K&N filter in yet (it needs cleaning) so running with a paper one in good shape. For good measure, I'll check the fender intake to see if that is clogged later today.
  
  I don't think I have a leak in the return line, but where should I be looking (i'm assuming around the pump and where it connects to the "solid" hose)?
  
  I drained the water from the water trap and fuel filter when I did the servicing and there has been no evidence of it leaking.
  
  I fill up with Diesel Max at Husky or Mohawk and add Stanadyne Formula to it. The other day I was very close to empty and only ran 650Km.
• #3 by jtanguay on 20 Jun, 2007 16:18
• sounds like the mileage i'm getting
  
  my tranny does not seem to be matched for the TD power though... what is your cruising rpm's on the highway?
• #4 by burn_your_money on 20 Jun, 2007 19:30
• Definitly get a compression test. Your engine is at the "critical mileage" where alot of the factory rings fail.
  Or, with the engine running pull the CCV off the valve cover. If you have white puffing smoke you have problems. Expect there to be a decent amount of air flow out the hole though.
  
  Look closely around the pump and injectors, the braided cloth lines tend to get brittle and leak
  
  As meantioned what RPM do you run at on the highway? If you don't have a tach climb under the tranny and get the code and your tire size. Then go to www.scirocco.org/gears and see what your engine speed is. Over 3k on the highway and expect about a 150km/tank hit in mileage, depending on how high it is of course
• #5 by 55mpg06 on 21 Jun, 2007 22:20
• Thanks for the replies. I will try to do a compression test ASAP (working on other cars) but for the time being I will try pulling the CCV of the valve cover tomorrow. Very cool trick . Unfortunatly I don't have a Tach yet just this HUGE clock where it should be  :? (that will eventualy change I hope), but I will definatly check the tranny number and the web link. I am running 13" tires (Mags left over from my 85) now instead of stock 14". Judging by the sound I deffinatly think I am in the mid to upper range of the rpm's at 110Km. The car really starts to howl at about 140 and it dosen't want to go much further. In town I can cruise along in 5th at 65km on flat probably around 1300 RPM if I was to guess by the sound.
  
  My friend had a 92 with AC and she got about 800-900km to a tank driving fairly agressivly on the highway. Just out of curriosity do the 92s have different tranny than the 90s. I know that 1990 is different than both of my dad's and grandma's 85s, my sister's former 87, and forssure (for obvious reasons) mom's 97TD (yes jettas seem to have been in the family for a while there have been even more :wink: )
• #6 by Doug on 22 Jun, 2007 03:51
• Okay then, it sounds like your vehicle is in fair shape but isn't haulng three adults and gear up and down the hills out of Kamloops asking a lot of a 1.6 diesel? This is like hauling a trailer. Unless you have a large displacement engine with gobs of torque at low rpm you are going to have to make it work. That will use fuel especially climbing hills and keeping the pace. Why don't you test it with a gentler run and no extra weight?
• #7 by zukgod1 on 22 Jun, 2007 07:09
• Have your injectors refreshed, 270’000km has got to be close to the end of thier effeciancy life.
  Take the timing back up a bit,
  Use a lighter oil, 15/40 is heavy. I use a 5/30 inthe summer and 10/30 in the winter.
  
  Good to go after that I'll bet.
  
  dan
• #8 by gratefuljoe on 19 Jul, 2007 00:04
• Hey guys,
      I've got a 91 golf 4-door 1.6 NA and the mileage comes in right around the same: 35 - 40mpg.
  
      However, I do have to admit of a heavy right foot...
  
      Top speed I've seen (down a BIG hill) was 155 km/h
  
      At full throttle, in the prairies, she'll do 120 - 140 km/h (75 - 85 mph) (depending on grade and wind) and we'll get about 27 - 30 mpg.
  
      At a reasonable pace, 110 - 120 km/h (68 - 75 mph), we'll get about 36 mpg
  
      And at grandma pace, 90 - 105 km/h (55 - 62mph) , we'll get about 40 mpg.
  
      The most I can hope for on most hills is for her to hold her speed.  Sometimes this is too much to ask for.  Leaving Kamloops, the best we could do was 85 by the end of the hill, that was in 3rd gear, screaming (1 passenger, camping gear).
  
       Should I expect more power and better mileage?  Or should I just be grateful, given my driving habits?
  
  Thanks,
  
  Joey
  1991 Golf GL 1.6 NA
  (turbo envy)
• #9 by gratefuljoe on 19 Jul, 2007 00:06
• 55mgp06,
  
  Please do keep the posts coming...
  
  I have the same - smoke between shifts - thing going on.  I'd love to hear about your findings.
  
  I have a suspicion that my injectors are wearing carbon hats.  I will soon inspect them and report back.
• #10 by burn_your_money on 19 Jul, 2007 05:01
• gratefuljoe you should be gettiing better then that. What transmission do you have?
• #11 by clbanman on 19 Jul, 2007 06:36
• I just recently did an approximately 1300 km trip into the UP in Michigan. Speeds were mostly 105-120 kph.  All highway.  86 Golf 1.6 NA with 338,000 km, and as far as I know the engine has never been opened up.  62 mpg (imperial).
• #12 by gratefuljoe on 19 Jul, 2007 08:58
• I'll get under the car and check the transmission number later, however, I can definitely say that she's NOT screaming in 5th gear - she seems totally relaxed and happy at 120 kph.  
  
  Also, once in a while, everything seem to "go right" and she'll make about 20 - 30% more power.  
  
  I wonder if it's time to pull the injectors?
• #13 by burn_your_money on 19 Jul, 2007 13:09
• Mine does the same thing where all of a sudden it seems like it actually has something to it. It's probably my injectors but it could be a slew of things. Even though my car gets great mileage it's needs all kinds of work
• #14 by rabbitman on 24 Jul, 2007 13:22
• Howdy 55mpg06, yeah, 35mpg is pretty low, I don't have a TD but I thought TD and NA got about the same mileage. Last weekend I went on a 450 mile round trip with 5 people in my NA rabbit and the trunk piled a foot from the ceiling and the mileage didn't change at all. I cruised 65-70 on the flats and 40-50 on the hills. I don't push it very hard at all, my max power gauge is the mirror(let it smoke just a little) :lol: Oh yeah, I have a rebuilt IP and injectors so I'm sure that helps. I also run No.2 diesel :twisted:
  Keep us posted, I hope you can fix it.
  
  PS.  On the way home a moose ran out and took off down the road in front of us and ran full speed into the ditch, tripped in a hole and totally landed on it's face and slid along the ground :lol:  :lol: I've never seen that before!! She didn't get hurt 'cause she bounce right up and ran off.