Hullo All,

I'm looking for the top 10 possible reasons I'm using huge amounts of fuel all of a sudden. dropped from 380miles a tank to 260 last week and 290 the week before. Useage has not changed at all. I don't think I'm burning any oil but the car smells rich, particulary when pulling up at the lights or stationary. Factor in a bit of a lumpy idle which may or may not be related.

I can rule out:

Leadfoot
Plugs (Changed)
Leads (Changed)
Airfilter (Freeflow fitted 12 months ago)

What else could it be? MAF? Gaskets? I have a report from somewhere saying the baffles in my exhaust are loose, could this be related? I checked my plugs after about 500 miles when I replaced the HT leads and they were black and sooty. seemed unusual after such limited mileage but if it's overfueling and for whatever reason, this could cause that right?

So, what am I missing folks? I have it booked into VW Poole for a VAG-COM next week but it would be nice to fix it before I have to part with £75 just for the pleasure of having someone plug my car into a 'puter.

Rgrds

David

moto1.8t:

Hullo All,

 

I'm looking for the top 10 possible reasons I'm using huge amounts of fuel all of a sudden. dropped from 380miles a tank to 260 last week and 290 the week before. Useage has not changed at all. I don't think I'm burning any oil but the car smells rich, particulary when pulling up at the lights or stationary. Factor in a bit of a lumpy idle which may or may not be related.

I can rule out:

Leadfoot
Plugs (Changed)
Leads (Changed)
Airfilter (Freeflow fitted 12 months ago)

What else could it be? MAF? Gaskets? I have a report from somewhere saying the baffles in my exhaust are loose, could this be related? I checked my plugs after about 500 miles when I replaced the HT leads and they were black and sooty. seemed unusual after such limited mileage but if it's overfueling and for whatever reason, this could cause that right?

So, what am I missing folks? I have it booked into VW Poole for a VAG-COM next week but it would be nice to fix it before I have to part with £75 just for the pleasure of having someone plug my car into a 'puter.

Rgrds

David

This happened to my old 2.0 Vitesse when the baffles were loose - the Lamda picks up a supposedly weak mixture and the ecu fires more fuel in to compensate. Either that or the CTS (coolant Temperature sensor) on it's way

Crikey, I thought I would have got a better response than this Have I posted in the wrong forum?

Since last post I had VW plug it in and it threw up poor signal from the air mass meter so I changed it. Fuel consumption got better but only by about 1/3rd. So I'm still using way too much and the car stinks.

Popped over to a guy who used to service the car and he plugged it in and wired up the MOT emmisions test and aside from a hideous fail it was getting no signal from the lamba sensor. I've had the lamba changed today and it's made no difference at all. Still drinking like a Scotsman on his birthday!! The guy at the garage did say the ECU was not getting a signal and that it might not be the sensor. Does anyone know of a common or possible fault with the ECU not getting signals through properly? Seems odd the Air Mass and the Lamba would happen to go at the same time doesn't it?

I've thrown like £500 at this so far and I'm not better off. Could the ECU have failed? It seems odd to me that the VAG com didn't pick up the lamba issue so could it be a wiring issue? Bad earth or similar? There's nothing else really left in the fuel metering chain I can think of...is there?

Hoping for a better response to this one. Can anyone help or suggest a solution?

Thanks

David

take it to someone who knows what there doing!!   change this change that sounds like guess work to me and costing you money... Might be worth you buying vag-com  great tool..... or take it to a specialist. 

You say the car smells rich? Can you smell fuel when you park up? Inside car or out?

You are right, it is a bit "throw money at the problem" but that's because I took it to VW and they told me it was the Air Mass meter. They I assume used the VAG-COM and it didn't show anything else up. I'm not sure how much more specialist I can get

How much are VAG-COM and where do you buy them?

D

Hi NooNoo

Fuel smell is outside. Example, pull up at junction with the windows open and you smell it.reverse into a parking space and when you open the door it's there. Letting the engine run does the same thing. Watching the guys with it on the MOT test rig a lot of soot was coming out of the exhaust after running it at high revs. I think the car is over fueling but it's getting to the bottom of why! Could it be ECU related?

 How many Lamba sensors does the car have? I changed the one in front of the CAT but a number of people, and the garage that fitted it asked me "which one?" when I called around for a quote. Most seemed, once they had looked at their parts system, to think it only had one but do some VW's have two? My Pulsar had it on the exhaust but my Fiat Coupe had it just below the manifold. Could the VW have both?

D

Are you sure you haven't got a "straight forward" leak? i.e not the engine consuming the fuel...

I had a terrible leak on the top of my fuel pump that resulted in lower MPG and fuel smells you described.

It easy to quickly check: -

1. Lift the drivers side rear seat bench forward.

2. Locate a flap in the rigid carpet material and fold away

3. Remove the 3 posi screws on the fuel pump assembly cover.

4. Inspect the top of the fuel pump for leaks.

My output feed on the assembly had fractured and fuel was leaking and pooling!

If it's dry then all well and good!

 hi,

 not sure on the 1.8turbo but my 1.4 had a dirty throttle body my car didnt stall it was just quite rough in idle. I cleaned it out their was a layer of oil and crap it in this improved my MPG

Hi NooNoo,

I might give that a look at the weekend but I don't think it's a leak. The petrol smell is largely at the back end, not under the bonnet or from under the car. After seeing it on the MOT test bed and the amount of soot coming out the back I'm convinced it's engine/electrics related. Two devices showing with no signal output in the past two weeks would sugest that as well. My concern is that it's ECU related rather than the peripherals that are showing up as faulty.

i might give the throttle body a look at at the weekend as I'm sure it needs cleaning but I don't think it would be having such a significant effect on the mpg and running and like I said, with the electircal gremlins as well I think it'll be something that way.

Does anyone know, does the MkIV have one or two Lamba sensors?

D

is performance flat? how many miles has the maf done? I reckon its worth doing the maf. 

moto1.8t:

Does anyone know, does the MkIV have one or two Lamba sensors?

the 1.8t's have 2 sensors - not sure about the other variants though mate, sorry

With the fuel pump leak the petrol smell is ONLY from the back end. Offside rear end stinks of petrol. I would definitely check it. I lost about 3mpg. I was horrified to see petrol pooled on top of the pump assembly. I shall post a pic tonight of what you are looking for...

it's a 1.8 non turbo, of course performance is flat!!

If by MAF you mean the Air mass meter (I say that as when I asked GSF for a MAF they tried to give me something very different), then I already changed it along with the plugs, leads and Lamba. no joy

this follows on from a thread about it having a really bumpy idle which may or maynot be related.

D

Cheers NooNoo I'll certainly have a look but I'm loosing waaaaaaaaaaaaaaaay more than mpg.

A full tank would normally do my 4 x 75m commute and leave me with just over 1/4 a tank to play at the weekend. Currently I can JUST limp home on the 4th day off the same full tank. I've lost nearly 100miles a tank although changing the Air Mass has rescued about 30 of those. I'm down a about 70 miles a tank ATM. Bummer huh?

d

Here are some pics of the fuel pump assembly under the rear seat bench. Even if it's not the issue I'm sure someone will find these pics useful!

Lift the flap under the rear seat bench ^^^

Remove the 3 posi screws to reveal the pump.

You can see the fuel pipes exiting the assembly. What happens is that the white moulded upper section has to be mounted with the large moulded arrow (you can't see on this pic) pointing to the back of the car. If it isn't then the fuel pipes are under tension and the moulded outlets fracture in time...

Cheers NooNoo. I may have a look since you took the time.. It's an excuse to do damage with some spanners. where should i be looking for damage/leakage? what to do if I have some?

It took 2 mins to take the pics!

The fracture occurs where the black/blue fuel line connectors attach to the top of the assembly. The only fix is a new fuel pump excluding sender. £167ouch! Its a shame as you only need the top moulding not the fuel pump itself. So I have a spare fuel pump now...

Ah well. Hope yours is dry!

You have said that you replaced the filter with a free flow filter a year ago, well i'd strongly recommend that you check to see if the filter is dirty?

 I'm unsure if you have an induction or panal filter, either way if it's dirty it will use more fuel to compensate for lack of air, the maf, and lambda sensors also control the fueling, also worth investigating the down pipe and manifold for leaks because not only can fumes escape but air can also be sucked in the exhaust can weaken the mixture and false the lambda this then makes the ecu bung more fuel in.

Also worth noting using a good injector cleaner like forte specialist injector cleaner http://www.forteuk.co.uk/ will help to lower emissions and running problems caused by stinking and blocked injectors, see the technical tips on the website you may find a vehicle with your symptoms and what the garage did to cure it...

I'm not sure if you've said if it will pass the emissions or not, but if it does pass an emissions test then this would conclude that the lambda is working correctly, 

Another thing is the petrol prices keep going up and it's false illusion to believe the fuel gage, the price is £104.9 - £106.9 per litre around staffordshire, and £50 worth of fuel only gets you 47 litres i remember the days back in 1999 when petrol was 69.9 and £50 would get you 71 litres 24 litres of fuel difference!!!!!

And if one goes back to 1987 when thatcher was in power petrol was 37 pence per litre so back in 1987 you'd be paying £18.50 for 50 litres, 21 years later were paying between £52 in the north and £69 in london areas!

 I hope this helps...

 also worth checking the fuel filter for leaks. mine was leaking for ages, was giving terrible mpg. i didnt even notice it really, it was just a gradual problem so i just didnt notice it.

was under the car and noticed a few things looked wet so started to prod a poke. removed the plastic wrapping around it and found something had punctured the casing. in the 12 mile round trip to halfords for a new filter, i used a quarter of a tank