20mpg factory fitted v40

[richjc4]

Can anyone recommend anything to help me improve my fuel usage before I sell for something more economical. I've had the car about 2 years now and get between 20-24mpg depending on the type of driving I do. I had the mot last week and the emissions wouldn't pass on gas so they had to put it on petrol which just came in bellow the upper limits. I'm running single electrode ngk plugs correctly gapped and have not long carried out a full service. Other points to note are that it never starts straight off the key always 5-10 seconds of cranking. Seems overpowered too. It is poor on fuel on petrol too. There are no engine management lights on. Any help greatly appreciated.

[capt jack]

If things are not good on both gas and petrol I guess you need to think about bits that are common to both.

That would include the ignition and exhaust systems, plus the air filter.

My first thought would be to check the air inlet and filter. If that's clogged then you'd certainly get the problems you've described.

Jack

[stevo48]

The 1st thing I would do is get rid of the NGK plugs and replace with genuine volvo plugs, you say the car has recently been serviced, was that a by yourself or a garage?
As above check ignition coils, fuel system, injectors, pump etc.
Which model V40 is it, how old is the car, how much mileage has it done?
With the bonnet up listen carefully for any clicking/rattling noises coming from the front drivers side of the engine, if you hear anything it is possible the vvt pulley is in ned of replacement which would account for your poor economy and high emissions reading.
Alternatively is your car the mitsubishi powered 1.8 GDI, as this particular engine has issues of its own.

[richjc4]

Thanks for the quick replys. I have the 1.8 factory bi fuel, not the gd engine. The air filter is new and I always change it on a regular basis. I believe the spark plugs are ok and are the recommended ones for lpg. Have tried the volvo ones and are worse if anything. I was thinking the leads coil or lambda sensor,however would these not throw up a management light. I've got a limited budget so can't really aford to change everything the car has done 142k

[chelle_belle]

May be worth having the lpg system serviced?

[richjc4]

Yes that is in the list but doesn't explain the poor starting. It's bad on the fuel on lpg and petrol. Might start with the leads and lambda sensior

[classicswede]

The NGK plugs will be right if they are the cheap copper core ones. Do not use platinum plugs with LPG.

I would run it on petrol for a while and see if it improves. If the starting ends up much better and the MPG improves then it could be an LPG problem. If things remain the same you will need to have the OBD read with a machine that does live component monitering and check all the sensors are reading correctly.

With the age and millage I would expect a blocked cat as a strong possibility. If it is down on power on both fuel that would add to the chances that the cat is teh problem. If it is the cat I would personaly de cat it.

There is a long list of possible reasons why the consumption (fueling) is so bad but it does need someone with a bit of experiance to solve the problem.

[richjc4]

Yes I'm using the cheap plugs as reccomended on here for lpg. Ill give the petrol a go for a bit and see if things improve. Will de catting effect the mot at all? saying that it only just passed last time. Ill get it plugged in sometime next week and get back to you with the results. Thanks for the tips.

I did ask an lpg installer about servicing my system but said there wasn't a lot he could do with the factory system other than change the part where the gas mixes which is very expensive apparently. he said these do play up

[classicswede]

Provided the emmissions are ok not having a cat does not affect the MOT.