Right lads and lasses got a feeling my coolant temp sensor is about buggered due to lumpy cold starting etc but my main query is would this affect my MPG reason being its steadily falling from 275 down to about 250 or less and this all coincides since the poor cold starts....

 

Yup, if it thinks its cold all the time, a lot of the fuelling strategies (like transient compansation and wall wetting functions - the EFI version of an old carb' accel pump) add more fuel, so you can expect a worse FE.

Simon

 

You really haven't tried to search the forum for an answer have you?

In future, try a search first - you'll probably find more detail than you expect

For example, these are all around MPG and not just the Coolant Temp Sensor - which, in my opinion, DOES NOT cause a lumpy start, that would be a lambda!

WRX MPG?

Cold Start Problem

Can a faulty Lambda sensor really affect mpg?

Very poor mpg...why?


I was told by a mechanic, that the engine coolant temp sensor, senses the temperature of your engine. So for example, when you start it from cold in the morning, it tells the ECU the engine is cold, so dumps more fuel - sort of like an auto-choke. Then, once the ECU notices the coolant temp sensor increase to a preset acceptable value, it reduces the fuel it puts in.

So, if you have a faulty engine coolant temp sensor, it will probably run rich, most of the time. That's what mine did.

Check the error codes before you do anything. It's really easy Jolly Green Monster has kindly written a guide - if you have a classic.

Enjoy.

 

come on guys, there is no need to be rude about it, Ideally yes it you could do a search for the answer, and if you don thappen to find then ask, but there is no need to be so blunt.

The amswer from experience is yes, it will cause a lumpy idle at cold, it will also make it more difficult to start at warm. Also you might find your rad fans are on from the moment you turn the key. You can get another from subaru for 28 quid, and it takes about 20 mins to change it, unless you have girlie hands, so about 5 mins. You want to look at the lambda too, thats the biggy for fuel consumption. Check your error codes tho matey.
Good luck

 

Apologies if mine seems blunt, was still pissed about GingerBoy on another post lol

Sorry ShoobyDoo.

Seriously though, check your error codes.

All the posts in my thread above make good informative reading. But the best thing you can do is check your error codes.

Also, from my experience, the faulty coolant sensor DIDN't cause a lumpy start.

So there's two differing views.

Best best mate is to check your error codes.

 

ha ha ha

Cost me £165 at ProSport in Stockport to get mine diagnosed and replaced.

 

no worries mate, i dont blame you, he was being a tit. It seems to me there are a lot of different symptoms for the same thing, so you can only realy go with codes. The rad fans seem to be an indiactor though, mine went mental when iturned the ig on.

 

Cheers for the relies guys a really big help,did try searching but only found bits and bobs nothing specific, All the best lads and happy motoring !

 

no worries mate, hope you get it sorted.

 

Me too!

 

Old thread revival.Should have updated to let future people know turned out to be using Tesco instead of shell.Went back to using Shell 3 tanks leter it was all sweet again...

 

That's nearly 3 years ago!


Thanks for the timely update though.