AAZ Poor Economy

[BP10000]

The car: 1995 Golf 4dr, 301000km.

In the two tanks I've filled since I bought the car, the fuel economy seems dismally low. I'm currently at 588km from full (just til the pump clicked, not full full), and the gauge needle is just about touching the red. I filled up last time at about 600 km and it took about 43L. That's 7.2 L/100km, 33mpg (US).

My driving habits are mostly very short trips, maybe 20min/5km, with maybe 2-300 km of hwy driving at 90kph. I've been very gentle on the accelerator for the most part since it's not really getting a chance to warm up, but I'll usually throw in a good stomp in the latter part of the trip. It does not seem to be producing any smoke.

There seems to be a small fuel leak, I think from the cold start ass'y, because I can smell fuel strongly between the pump and block, but not too much in the engine bay at large. There is not enough leaking to form drips, but there is a definite fuel odour coming from the vents when idling at lights and such.

The idle is set at about 1050 rpm when warm. Starts ok in the cold, -8C today, the engine catches right away but the idle is rather "lumpy". the cold start seems to make a difference smoothing out the idle but not appreciably increasing the speed. After about 5 minutes of warming up (driving) the cold start makes no audible difference in idle speed whether in or out.

I've turned up the fueling ever so slightly, so that the idle of 1050 rpm is reached with the idle setting screw about halfway through it's travel, but as I said, no smoke even under hard acceleration once warm. The accelerator limit switch has been removed and left open.

So what are my prime suspects for causing this? I don't need to set any records, but I'd like to get up to average economy.

Driving habits?
Alignment/rolling resistance/my one bad wheel bearing?
Timing?
Something I'm missing?

Thanks for reading,
Bri

[8v-of-fury]

Bad alignment, a blown wheel bearing.. or maybe sticky back brakes.. all cause significantly reduced economy.. then throw in there that it may be bad timing.. you could drive that thing under 80 everywhere and never see over 40 mpg sadly. Have you had any front end work done recently? struts, bj's, tie rods? Get the wheel bearing replaced and get it aligned at the same time. Jack up the ass of the car and see with the ebrake off.. if the wheels have any sort of resistance.. or will they spin freely a few revolutions? If they don't i would look at your rear brakes.. maybe not fully releasing after removing the e-brake.. or maybe there just done in..

what PSI do you run in your tires? lol i always have been told to run 1-2 psi above the tires rating for improved mpg.

What kinda revs are you sitting a t while cruisin the hwy? Maybe you have a close ratio trans? (im not to big on mk3's but possible at all?) Do you drive with your windows down and the a/c cranked?

I dunno maybe your engines just old.. could be like some serious blow-by in the cylinders... a tired pump... it could be a lotta things.. hopefully somebody that knows more bout the AAZ will chime in with more engine related problems to look for.

good luck

[vanbcguy]

BP10000, you and me are going through the same thing right now!  I've got basically the same car (although I've got a 1.6 swapped in to mine) and it sounds like both of us have the same driving habits, plus we're getting the same mileage...

When I got my car it had a K&N air filter on it that was absolutely FILTHY.  I just put a factory air box on it with a shiny clean new filter and it SEEMS like it's helped - I'm not sure since I was doing some electrical work on the car at the same time and reset my trip odometer.  But that's something to check too - restricted air = bad mileage.

[jtanguay]

BP10000, you and me are going through the same thing right now!  I've got basically the same car (although I've got a 1.6 swapped in to mine) and it sounds like both of us have the same driving habits, plus we're getting the same mileage...

When I got my car it had a K&N air filter on it that was absolutely FILTHY.  I just put a factory air box on it with a shiny clean new filter and it SEEMS like it's helped - I'm not sure since I was doing some electrical work on the car at the same time and reset my trip odometer.  But that's something to check too - restricted air = bad mileage.

restricted airflow on a diesel = black smoke out the exhaust... so if you're not seeing black smoke, or feeling the car bog too much, i wouldn't worry.  but you must pay attention to the smoke the car makes to know.

my best guess is that your pumps internal pressures are not where they should be - a fuel leak/bubbles going to the pump would be a very good indication that the pump will most likely not be able to build the proper pressure for the dynamic timing.  alignment/brakes/bearings should account for about 5 mpg or so unless they are really bad, but then they would be very noticeable.  when you mix in low tire pressure though, the figures turn wayyy lower... like -10mpg or more... this is called low mpg sauce, and it tastes awful!!!  :lol:

[BP10000]

That's funny, I reset my odometer by accident too on the last tank. Fixing the highbeam bulb. Luckily my odo was at ___195 when I bought it, so it was pretty easy to work out how far I'd gone when I filled up.

I think in my case alignment is the most likely culprit. My vehicle was lowered by the previous owner (thankfully with proper springs and struts) and the summer tires that were on when I picked it up showed pretty bad uneven wear. I guess I just didn't believe that this would increase my fuel consumption by a good 30-40%. Maybe it's a few things combined.

I'll have to have a look underneath and make sure everything's tight then take it in for an alignment. I have a new rear wheel bearing, so hopefully that's the one that's bad.

I'll update when I get this done and see if it makes a big difference.

[arb]

What tranny do you have ?

On your rear bearings, did you jack up the car and spin the wheels ? they should spin freely. It not, brakes / bearings are at fault. I've seen mechanics improperly install roller bearings too tight.

Describe the uneven wear on the tires - alignment problems show up on the tires.