Poor fuel consumption

[bstardchild]

Well I've constantly moaned about the poor fuel consumption on my Polo 1.4 8V - sure you can get it to do nearly 50mpg but it's not exactly fun - and it's a whole lot worse under the same conditions than my old MKII 1.3 coupe S.....

It didn't help the mpg when I stuck the 195/45 15's on the car - previously it was running skinny tyres on 13' alloys.

Another thing that doesn't make me happy is it's unwillingless to sit at a happy speed or revs....

Well experience with other cars points me in the direction of the Lambda sensor but it didn't seem to switch that slowly.

Found a cheap VAG one brand new on ebay so stuck in a bid and won it....

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... RK:MEWN:IT

Yes I know my engine is an AEX but it's only the length of the lead that changes and I'm perfectly capable of coiling up a lead and making it secure

Well having done the rear wheel bearings today I had a bit of time left over to do the lambda probe.

As usual it was in the manifold good and tight and the only thing I could get on it was an adjustable and that was just trying to round of the edges of the hex section so resorted to the old fashioned approach - cold chisel the metal section containing the ceramic heat protection off and use a 24mm socket and 3 ft breaker bar on the remains to get it out.....

New one fitted and a quick run up the local bypass revealed a huge improvement - holds a steady revs and speed without any variation and performance is maybe slightly better - doesn't hesitate as much as it did and it's not so variable.....

This tank is shot to bits but I'll be interested in seeing what the next tank is like especially as I am now back down to 185's on 14' rims

[Speedlaw]

Interesting writeup mate. eBay can be a real winner.

[AKs_SlickPolo]

i think i got the same fuel consumption problem...can get around 200 miles from full tank to reserve. Is this good cos i dont think so. some one on the forum told me that it may be my lambda probe gone. Can you tell me where it would be and how can i change it...is it simple?? is there a way of checking that ure current 1 works?? i replaced the fuse for it 2day, and it seems to have made a very slight difference strangely, eventhough the fuse it had hadnt blown. Any ideas how i can get my fuel consumption sorted, i still got the 13 inch steel vw wheels as well. thanks

[AKs_SlickPolo]

sorry says it in ure posting already

[bstardchild]

i think i got the same fuel consumption problem...can get around 200 miles from full tank to reserve. Is this good cos i dont think so.

Doesn't sound very good - it's a 40 litre tank plus a bit so the maths doesn't look good either

some one on the forum told me that it may be my lambda probe gone

It could be - Polo's aren't as easy to tell as some cars when the lambda is getting lazy

Can you tell me where it would be and how can i change it...is it simple??

In the cast exhaust manifold - threaded in - see above description in my earlier post

is there a way of checking that ure current 1 works??

Well like I said - Polo's seem to be very tolerant of tired lambdas but heres how I decided mine was getting long in the tooth

Engine up to temperature

Handbrake on and out of gear

Hold your foot steady on the throttle and bring the revs up to around 2000 rpm - then try to hold your foot absolutely still

If the engine revs stay constant - Lambda is switching correctly

If the engine revs rise and fall slowly over a 10 sec period (say 100 rpm either way) it's on it's way out... It will only get worse

If the engine revs refuse to settle or rise and fall slowly over a long period it totally goosed and very lazy - replace it....

i replaced the fuse for it 2day, and it seems to have made a very slight difference strangely, eventhough the fuse it had hadnt blown.

Shouldn't make any difference

Any ideas how i can get my fuel consumption sorted, i still got the 13 inch steel vw wheels as well. thanks

So at least drag won't be a problem

[bstardchild]

sorry says it in ure posting already

See Above

[AKs_SlickPolo]

Hi, thanks, is the exhaust manifold where the warm air pipe is. As to the right of the pipe slightly below, there is something that looks like the lambda probe?? is this it?? Also if my lambda probe was gone, wouldnt it have blown the fuse as well? as eventhough i replaced the fuse yesterday, it wasnt actually blown. thanks

[bstardchild]

Hi, thanks, is the exhaust manifold where the warm air pipe is.

Yep - heat shield is mounted on top of the manifold

As to the right of the pipe slightly below, there is something that looks like the lambda probe?? is this it??

4 wires in - Hex nut on a 3 inch tube - that would be it

Also if my lambda probe was gone, wouldnt it have blown the fuse as well? as eventhough i replaced the fuse yesterday, it wasnt actually blown. thanks

Lambda's don't fail in a way which blows a fuse

OK what does it do (I'll try not to get too technical here)

- It works on a hot wire principle (measured voltage supplied to the wire)

- when excess oxygen is present in the exhaust (running lean) the wire burns brighter so resistance is lower - the ECU takes that signal and adjusts the mixture accordingly by increasing the duration of the injectors.

- when very low oxygen is present in the exhaust (running rich) the wire burns dimmer so resistance is higher - the ECU takes that signal and adjusts the mixture accordingly by decreasing the duration of the injectors.

Measurement cycle is a constant loop so it is adjusting all the time.....

You need an ocilascope to see the thing in operation - I don't have one....

What happens when the lambda sensor gets old is that the switching gets slower and as a result the adjustments are slowed too. As a result it (the ECU) overshoots at either end of the scale oscilating between rich and lean - not good for fuel consumption

If it's really knackered you can actually feel the car accelerating and decelerating on a straight flat well surfaced road with a constant throttle opening...

Hope this helps.

[AKs_SlickPolo]

Hi i did the rev test as you said, to find that my car holds its revs perfectly without cutting out or bouncing up and down. Does this mean the lambda probe is fine. I lifted my bonnet as well to discover the lambda thing. Here i found that it looked practically new, with a shiny golden body and a clean black wire sheathing with a few dust particles. It doesnt even look old. However fuel consumption is still ridiculous. Could this still be this??? or any other possibilities or leaks.

I filled up this morning and did 36 miles after. i filled up to the notch b4 full tank and it droped after 36 miles to 3/4.

I have the new type dash panel which is the airbag light intregated rather than the one below the back window heater and hazard light switch of the car. I have heard some problems with the petrol meter in 1 of them. Could this b possible in mine, eventhough i have the new dash 97/98 >.

i have noticed that it tends to bounce up and down....is this normal or a common fault...any cures.


Many thanks bstardchild for your help.

[13twelve]

if i hammer my car i get 200 miles to a tank


if i drive like my dad i get 300 miles


if i do a mix i get between 260 and 280 miles

(tank being full to redline things)




my mate in his 306 gti-6 gets 260 miles on 45 quid of petrol
haha thats half what i get

[AKs_SlickPolo]

Ive been doing a mix of both as well and have managed to get 80 miles w/ still just about 3/4 of the tank left. Glad 2 know its not just me getting 200 miles from full tank whilst booting it. I dont know though if this still sounds right. I heard polos are much more economical than this.

I am trying to install a universal induction kit. I am after the sounds but a m8 said this can reduce fuel consumption as well, is this true?? any1 noticed this?? does any1 have a pic of their engine bay, just want to know how to place induction kit.

Is there any other things except lambda probe, that can be the cause of my car drinking irracticaly (petrol obviously lol)?????

[AKs_SlickPolo]

13twelve, what size is ure engine by the way?? is it same as mine...1.4 CL??

[BenMMellor]

I can usually get between 350-400 miles on a tank in my 16v - a mix of usual motorway driving and a bit of town... Worst I had was when the fuel filter cas corroded through. Managed bout 150 miles on a tank !

Might be worth checking you aren't suffering a small fuel leak somewhere.

The only modification I've done is a K&N panel filter..

[13twelve]

mines 1.4 8v with a k&n

and the k&n has probably made my consuption worse

[AKs_SlickPolo]

Ive heard induction / air filters improve in lowering fuel consumption though. thanks benmmellor for that. Can you tell me where the fuel filter would be..i never though about that, it might be the fuel filter that needs attention. Please break it down for me as to where it is, as im not much of an expert in engines.

In terms of leaks i have parked my car in a part of my driveway where it is virtually spotless. This is so that i can see any leaks. However where would any fuel leaks be likely to come from. Below under front engine area, and near the back right handside?