97 Golf MK3 has very poor fuel consumption

**beeson** · 09-02-2008,02:46 AM

Hi folks,

I've owned my 97 golf 1.8l for only about 2 months now and I'm getting really bad gas mileage. I average 275 kms per tank...thats only around 20 mpg. So far I've changed the air filter, spark plugs (which looked totally normal before I swapped them, tanish/grey) and I ran injector cleaner in the tank the second last time I filled up. The engine doesn't over heat, and sounds normal. Does anyone have any suggestions before I take it to a mechanic? Thanks in advance.

**BugsyMalone666** · 10-02-2008,12:58 PM

Depends on what sort of driving your doing? Local driving round town (like 2 miles between work and my house) if i do nothing else but that sort of distance with maximums of 5 miles fuel consumption was about 25mpg tops!

when i got my golf several years ago on the first few long runs i did it was averaging 38-42mpg! then i started driving it harder and fuel consumption went down, although when I started seeing my g/f 220 miles away with such long trips i tended to try and economise and saw a maximum of 34mpg!

what i have noticed on the MOT`s is that over the past few years the emissions have gradually been rising very slightly until this year when it was almost a fail!

you say you car doesnt overheat, does it run at about 80-90c? mine was running just off the 5 bars at the bottom on the motorway which means then the engine thinks its still warming up and uses more fuel.

I have since replaced the tthermostat which improved the temperature and also I changed the exhaust oxygen sensor which I havent been able to test on the 220 mile trip yet but local 35 mile runs thrashing it, it still seemed better on fuel although I have yet to take it back to my mechanic/MOT station to test the emissions.

having done a little reading it would appear that as the exhaust sensors age they deteriate causing higher emissions and higher fuel consumption, although what i have read on the internet it reckons they only last about 50k, my golfs on 105k!

**beeson** · 10-02-2008,03:54 PM

Hey, Thanks alot for that Bugsy. I took a trip yesterday to Toronto and back (so mostly highway driving) which is about 220K round trip and I still averaged about 300 km (186.5 miles) on a tank, which is only about 17.6 miles/Gallon. It's funny you mentioned the temperature, because I monitored that the whole trip. I didn't realize that low temp would increase gas mileage until I read it somewhere yesterday. When I start the vehicle it seems that it gets up to normal temp but then it will drop shortly after to about 70-75. It seems to come up a bit if I'm not on the highway and I'm idling. Is it possible the thermostat is just sluggish in closing? I will replace it this week, I bought one with a gasket a while back because I had a small fluid leak but it turned out that it came from the water outlet elbow and not from the thermostat, so I never did replace it...sort of wish I had now.

As for the O2 Sensor...I've read alot about this and that it's a big contributor to fuel consumption but I find it hard to believe it's having problems since I passed the emissions test not even a month ago, AND I've had poor fuel consumption ever since I owned the car. But seriously, I'm not sure how I passed emissions anyway with that kind of gas mileage. Also, I have a chance to pick up a code reader for like $70 CAD at a local shop, would it be a wise idea to get that or would it likely not tell me anything? Thanks again brother, it's very much appreciated.

*forgot to mention the car has around 200k.

**Crasher** · 10-02-2008,04:29 PM

Do you mean US or Imperial gallons? I think you use Imperial Gallons in Canada but I am not sure.

**beeson** · 10-02-2008,05:01 PM

Hey Crasher, I did the conversion in US gallons. thanks.

**Crasher** · 10-02-2008,06:20 PM

1 Imperial gallon is 1.2 US gallons so the figure will appear 20% worse to us than it is to you.

**beeson** · 10-02-2008,07:18 PM

Just my luck...I start driving my car this morning and now there's a big banging coming from the rear left wheel whenever I hit bumps, even the tiniest cracks in the road. It boggles my mind that I didn't have any problems last night before I parked the car...the only difference is that it's really cold outside today...but I think my rear left shock is now on the fritz...as far as the Haynes manual suggests, it's not that big of a job...just one more thing I need to do now. : (

**Crasher** · 10-02-2008,07:24 PM

Or the exhaust hitting the axle. Mind you, I have no idea what the temperatures that you are subjected to can do to a car. To us really cold is around 0 degrees centigrade, that’s probaly T shirt weather to you!

**beeson** · 10-02-2008,07:58 PM

hehe, yeah it would be T shirt weather right now...it's -14 c, but "it feels like -25 with the windshield"... if the weatherman says it feels like -25, then why don't they just say it's -25?

Anyway, the clunk is a hard clunk, you can really feel it. So I would guess the shock, but I'm really assuming at this point...I need somewhere warm where I can have a good look at it... what else could it be really?

**BugsyMalone666** · 10-02-2008,08:14 PM

Originally Posted by Crasher

1 Imperial gallon is 1.2 US gallons so the figure will appear 20% worse to us than it is to you.

its still bad MPG however you look at it!

Beeson, the thermostat I would replace, its a relatively inexpencive part and when I tested the old one it seemed to work ok, but had the same symptoms as you describe. On the motorways it would go right down and the only time it would get up to operating temperature is when its warm and sat in traffic at idle. The new one didnt noticed the difference until I took it on the motorway and got it upto temperature and it actually got to optimal temperature.

as for diagnosis reader, I have VAGCOM and an ODBII cable (your 97 will be ODBII but my 94 is only ODBI so there maybe additional features you can read) but having it plugged into the laptop and driving along the motorway I did a data log, then when I got home I plotted the results but the only real thing that was noticable on the results was a slightly low engine temp(due to the thermostat) when I changed the exhaust sensor however what I did find was that the results were more stable from the sensor.

Im not sure what your emissions regs are like or your last read out but here CO2 must be under 0.20% which over the past 2 years I have seen rise from about 0.14% to 0.19% then last time we checked it was about 0.35% and it wasnt stable.

in the past year we have had some batches of bad fuel here which have killed a few peoples exhaust sensors and im guessing it also damaged mine with the sensor not giving a good reading its not bee running right although to drive it you would notice.

as for your clunk, something I would check which is really easy one is the exhaust heatshield by the fuel tank and where the axle is near the exhaust, on my golf I get a sort of knock and its a combination of the heatshield missing a retaining clip making it closer to the exhaust then when i hit a bump the axle touchs the exhaust and then makes it knock against the heat sheild ( i should probably mention I have lowered it about 50-60mm)