Low mileage - ECU / fuel optimisation issue?

DevCoder

Hello

Living on a 9x5 mile island we drive very short distances (mostly less than 3-4 miles before stopping then 3-4 miles return). Sometimes is less than 2 miles or 10 mins

Ive read that this can cause issues as the ECU doesn't have enough time to optimise the fuel flow so fuel economy is poor.

Firstly, is this true? Secondly is there anything that can be done?

Its a rav 4 if that helps.

forgotmyname

No The ECU learns over time. Unless your resetting the ECU every journey it will learn.

The short journey's your doing are the cause of the poor MPG.

Rav 4 not the most efficient car also.

For journeys like that you want the smallest petrol engine you can get, In the lightest car you can get.

The engine probably never gets properly warm to burn off the contaminates in the oil / engine breathers.

Older carb fed engines used to get something called bore wash. With a cold engine and the choke on it could overfuel and wash the oil from the bores of the engine. Removing all lubrication.

Engines would not last as long as they do now. Fuel injection helped that but its still a slight issue where an engine that does lots of short journey's and never getting properly warm wont last as long as one that does.

colino

Most modern cars with a plethora of electronics do have learning phases for the main ecus (especially automatics). but the additional issue you have is that few small islands will have the length and diversity of roads for that action to take place. Say the Island of Bute with not even a bit of dual carriageway and few real straights, the engine will generally be running in lower gears and higher rpms than a motorway muncher on the mainland. The car will stick to its default settings (which are normally for comfort, not economy) and you have a double whammy of a car not running optimally and in less than ideal terrain.
You could search for the Toyota recommended relearning procedure and head for the mainland, but would the additional time, petrol costs and ferry fare justify it?

BeenThroughItAll

Your driving style and choice of vehicle are the reason behind the poor economy. With that type of use, notwithstanding the fuel economy issue, I'd be changing the oil every 3K miles too, personally (unless of course you're not intending to keep the car for any significant period, in which case you can leave the potential problems to the next owner, who will doubtless think they're getting a low-mileage bargain).

DevCoder

Many thanks to everyones response.

The car is serviced yearly complete with an oil change, we are probably averaging 3K-4K miles so hopefully an oil change in that range should be ok.

I know the choice of vehicle is poor, we picked it when we had a child as it meant loading the pram was not involving the wife bending over to place the pram into and pull up out of a recessed boot.

The island (Jersey), has one dual carriageway where max speed is 40mph, most of the other roads are either 30mph or 20. Very few are down to 15mph.

We've had the car for 8 years without any major issues although late last year all 4 O2 lambda sensors went (pretty much one after the other) so that was the first replacement parts as such.

So a 12 year old car and its done 34K miles in total (all on this island), fairly sure its thinking where the hell it is and why it cant go any faster the poor thing.

colino

While some might argue that four sensors failing at the same time will be due to the scrupulous engineering standards of manufacture, I would take that as a garage desperate to extract cash from a customer.
All four O2 sensors failing around the same time - just doesn't happen.

forgotmyname

Changed all 4 sensors, Possibly couldnt be bothered to test to see which one was causing it or failed to diagnose the problem properly.