Variable Fuel consumption

[Toad 0]

Righty. I've got a 1.8 valver, and my fuel consumption recently has been RRRRRRRubbish, about 28-29mpg. The car's been running quite poorly too. A couple of wekends ago I decided to clean the K&N, which turned out to be properly filthy and fiddle with the mixture according to KevHaywires instructions from a thread from ages ago. And it was brilliant!! She went really well, and the economy was 34-35Mpg.

 

However the economy has dropped right back again to 28-29mpg. I've not been driving it differently. Same sort of journeys etc.

 

Also the ISV is on its way out, sometimes I've got to heel & toe her for the first couple of miles until it's warm, and it will idle by itself again. Could this have something to do with the poor economy? perhaps the ISV sticking open and making it run rich or something??

 

The mpg figures have been from the MFA, which I know isn't the most accurate source, but the figures seem to tie up with the actual fuel consumption.

 

Any Ideas??

 

Thanks

 

Tom

[Yandards 0]

I would try to 'prove' the figures from the MFA first by running a couple of tanks and working out the MPG that way.

 

You can try cleaning your ISV, there is a thread on here somewhere about it, the other issue maybe that your mixture screw is coming loose again.

 

Another thing to check would be tyre pressures, especially at this time of year as the falling average temperature will start to knock them down quite quickly.

[Toad 0]

I would try to 'prove' the figures from the MFA first by running a couple of tanks and working out the MPG that way.

 

You can try cleaning your ISV, there is a thread on here somewhere about it, the other issue maybe that your mixture screw is coming loose again.

 

Another thing to check would be tyre pressures, especially at this time of year as the falling average temperature will start to knock them down quite quickly.

 

I'll do that. My tracking is also a bit wayward, which could also do with sorting I suppose.

[davidwort 0]

a lot depends on your driving style and journeys, a 1.8 in good condition on standard tyres driving on the motorway at a steady cruising speed can easily reach 40mpg, driving around town the torque curve, gear ratios and weight of the car mean you can barely reach 25mpg in some situations.

Brim to brim is the best way of working out mpg, the MFA's vary a lot but are almost always over optimistic.

With the K-jet system on a 1.8 16v warmer weather makes a big difference on fuel consumption through the warm up phase.

There's so much that can affect mpg, wheel alignment, injector spray pattern, timing (ignition and engine), binding brakes, partially blocked/blowing exhausts, manifold vacuum leaks etc...

 

David.

[double-6s 0]

My blue vr has a hole in the downpipe which has a fairly marked affect on fuel consumption. I think the lambda senses loads of air coming from the hole and assumes its running lean, so richens up the mixture? Hence sh*te mpg?

[dr_mat 0]

The weather makes a big difference to the economy, particularly if you're doing shortish commutes.

It's five degrees colder these mornings than a month ago ..