more details of the car please? engine & miliage etc

 

I think he gas a 1.4.

I've always found that 1.8 120 is best for mpg.

 

79k 1.4. Thought I was using a lot of fuel :/

 

What sensors on the k series can directly affect mpg? Does the thermostat affect it all the way through a journey or just cold?

 

I'n not sure there would be a sensor, the thermostat wouldnt effect it.

When was the car last serviced?

 

It had a service last may. But surely a drop that bad wouldn't be from just a service? I've ordered an air filter to replace, doing an oil change sometime this week, and hopefully coolant when I replace the radiator and thermo. Spark plugs, battery? Oh, my interior lights dim when I use my headlights, I'm thinking the alternator. Would that increase mpg?

 

fuel filter would be a good place to start, and spark plugs how many miles as it done since may?

Alternator i suppose if you think logically its belt driven from the engine, if the bearings are sticking its putting greater force on the pulley and causing drag/friction meaning a greater force is needed to over come so could cause a slight impact to MPG

What people also often forget is really the 1.4's are city cars and are not really built for motor way driving.

 

What people also often forget is really the 1.4's are city cars and are not really built for motor way driving.

In no way. shape or form can the 25/ZR be considered a 'city' car.

29mpg is a lot les than I would expect from a ZR 105, even with a heavy booted driver at the wheel. On a long steady motorway run I would expect nearer 40mpg. an overall average in all driving conditions, perhaps mid to high thirties.

There are any number of things which could contribute to higher than expected fuel consumption, and it may well be a combination of things.

Low tyre pressures (or even the tyres themselves) can affect fuel consumption, but on their own, even tyres which are half flat are not likely to give a massively noticeable higher rate of usage. Likewise, if the brakes were binding to that degree, you would notice the braking effect at low speeds, and would feel the heat from the wheels.

Sensorwise, a faulty engine temperature sensor (on the coolant elbow at the front top right of the engine as you stand in front of the car) could make the ecu think the engine is cold and increase fuelliing, or a faulty lambda sensor could also give misleading information to the ecu.

A failed (permanently open) thermostat will make the engine run cooler than normal, which in turn will affect fuelling via the information the ecu recieves from the coolant temperature sensor. This affect would be more pronounced at higher speeds where there is a high flow of cooling air through the radiator. If the thermostat has failed and is permanently open, you will find the temperature gauge will fluctuate whilst driving - it will rise to the normal position (just below the halfway mark) at low speeds or when at a standstill, but will drop back at higher speed.

The heater staying cold for 10 minutes sounds a bit unusual - some slight heat normally starts to be felt from the vents after only a few minutes, and the heater should be producing fully warmed up air within the ten minutes you refer to. However, as yours is a Mk2, lack of heat from the vents, or only getting heat at higher speeds, could be due to a failed SAAB valve which doesn't affect the engine temperatures at all.

If the car has had a service only a few months ago, and had the oil, air filter and plugs replaced, I would think it unlikely that a service again would make any difference. An old fuel filter which is becoming blocked is likely to see reduced engine performance rather than higher fuel consumption.

 

I disagree. Mated to the right gearbox the 1.4 is great for the motorway.

Even in a metro gti @4k you can get 42mpg.

I'll price up everything and see. The belt slips sometimes cold, and sometimes changing gear at high revs. Just wondering if that is similar to what you describe. Maybe it isn't gripping like it should

 

Iirc, was on 65k or so in may 2013, service includes water pump, cam cover replacement, amongst other little bits. Service intervals are 12k/year for oil if I read correctly? So I know it is due a service, but not as bad as some cars will. I'll try an oil change tonight if I get back in plenty of time for the engine to cool, but I doubt that'll solve anything

 

another thing that could effect MPG that often gets overlooked is tyres - pressure and grip

 

Check the tyres are properly inflated, pointing the right way and the brakes aren't binding as well as things like oil level, plug condition and filters.

My average economy over a tank measured brim-to-brim in my 1.8 ZS varies from 32 mpg (commuting 10 miles each way, congested roads and cold temperatures) to 48 mpg (motorway runs to North Wales)

How and where you drive can make a massive difference to economy.

 

my last brm was doing 18 mpg :rofl:

 

does the exhaust fumes smell rich?

 

Weirdly I did pick something up yesterday. Smelt a bit like like an SPi Metro GTI! (no cat) I'm not sure what "rich" smells like, but it didn't smell as it should

 

Would the torque app not show up any problems with the lambda sensor? And temperatures display on the app too. What should I be looking to achieve on a moderate drive, 20 miles?

 

i would start with Tyre Pressure -> Fuel Filter -> thermostat

 

Tyre pressures I had at 32. Will check them in a bit when I go out. Does 32 sound right for motorway driving?

 

sounds about right, but never owning a 1.4 mg-r couldn't be certain

 

I'll make sure they're 32 all round, get back on the motorway and report back. Doubt it'll make much difference.

Right brake seems to stick on when I moved it by hand over the weekend. You can hear it binding, and prolonged use gets it squeaking, so I suspect the disks are warped, but I'm fitting 120 brakes soon anyway so I'm not buying new discs now

 

Right brake seems to stick on when I moved it by hand over the weekend. You can hear it binding, and prolonged use gets it squeaking, so I suspect the disks are warped, but I'm fitting 120 brakes soon anyway so I'm not buying new discs now

Well that won't help your mpg at all...

If it's binding when cold you can guarantee it bites harder once it gets hot (which it will do, quickly).

In simple terms some of the energy being released burning the petrol is being used to heat the brake disc rather than keep you moving.

When you replace the discs make sure the mating face of the hub is as clean as possible so the disc sits true, give the sliding pins a once over (clean & re-grease) and make sure the pads aren't sticking in the caliper and can move freely.

 

that wont help mate, i think its a combo of lots of little things - started with the cheapest and work your way up the list

 

Yeah. I'll keep telling myself £995 was a good price??

 

sod's law mate

 

i would also avoid using as much as possible until brakes are sorted buddy

 

Yeah, hopefully have some new ones on by next week. Until then I only need to drive around town

 

I'd start with a new coolant temperature sensor and thermostat. Here they are:
Thermostat - K Series
Coolant Temp Sensor - MEK000030 - K Series

Cheap fixes to try first.

 

Fix the thermostat, it should warm up quicker, and when warm stay warm and the ecu will fuel the engine correctly

if the thermostat is open, and therefore overcooling, the ecu thinks the engine is cold and will increase the amount of fuel going in, hence your poor mpg

 

Messy job and I'm scared of it! I know that there can be trouble if you don't do it right. But then again, I wouldn't trust a garage either. I'd need someone who knows k series that could give up some time and unfortunately I don't, so for the time being it might have to wait...

 

Just as a comparison mines a 54 plate ZR160, just a shade under 100k on the clock, no history but i get 32mpg consistently at motorway speeds. My 03 plate TF135 with 78k and full history on the clock returns a consistent 35-37mpg. My last Mondeo 10 Plate 2.0 Ecoboost auto with 44k miles returned a consistent 29-30mpg.

 

put your location in your profile and I am sure there will be somebody in your area that might be able to help you

 

DN14, won't disclose it fully but quick access to M62

 

I might aswell get an order in before christmas for the cooling system instead of waiting. Up to now I have coolant, radiator, thermostat. What else would be worth replacing, even if it doesn't need it?

That is, aside from other service parts which up to now include front pads and disks, oil/pollen/air/fuel filters, oil change, brake fluid

 

If I end up doing the cooling system myself, if I follow the stickied guide exactly am I likely to run into trouble? The car is currently running fine, just with the weird heater problem which is one of these sensors hopefully