Hi all,

I've been having some mileage issues with my car. I have a 1.4 Mk6 on an 02 plate with about 40k miles.

I've done the timing belt, full service, new plugs and leads about April time. 

Over the past few months I've been getting horrific mileage. I have another 54 plate 1.4 fiesta on similar miles and that does 450-500 miles a tank however the one in question barely manages 250 miles a tank. 

It has another symptom of intermittently not starting. Like it will fire once then cut out and then take several attempts to start. But other times it will start right up. It doesn't matter if it's hot or cold. 

I've had the codes read and there's nothing, I've also had live diagnostics on when running and there isn't anything glaringly obvious from the readouts. The only slight oddity is the lambda is dipping into lean but it's correcting itself instantly which I assume is evidence it's working properly. 

Does anyone have any ideas? 

 

Many thanks 

Sure it's not leaking?  Petrol evaporates quickly so you can't always see a slow leak from a quick glance.  Should be able to smell it before the first drive of the day though.

Seems odd that it's using so much fuel without putting the lambda readings out of spec.  Suggests that it's not being burnt.  Unless the lambda is faulty I guess.

I have fixed a high petrol consumption issue like this with a replacement MAP sensor but the excess fuel was easily noted in the lambda reading on that car.

Check the throttle body and T-Map sensor. Both are fairly easily removed and cleaned. Lots of how-too's on YouTube. Once both are cleaned you have to perform a basic calibration for both to relearn basic values

Have you looked at the black rubber pipe under the inlet manifold? They slpit and collapse causing your issue's. If you shine a torch you can normally see it ok. Do it with the engine running as this is when it sucks itself in.

Please keep this updated if this is the fault for other readers in the future.