[Johnnybhoy7]

Looking to pick the minds again of some of the helpful experts on here!

Car mpg still seems to be pretty low. 100mile round trip to day. Basically sat at 70 on cruise control the full way as traffic was low. All motorway. Glasgow to Edinburgh and back and only returned 37mpg

Both thermostats have been changed car sits at 88 degrees

Car is regularly serviced

Glow plugs and relay replaced

Cars been terracleaned

Not a single fault code showing up

Any help appreciated!

[borinous]

is it remapped?

other things it could be (but not 100% sure if they would impact fuel ecomony)

EGR issue? stuck open or closed?
injector issue?
sticking handbrake or caliper? causing drag

[Johnnybhoy7]

Originally Posted by borinous

is it remapped?

other things it could be (but not 100% sure if they would impact fuel ecomony)

EGR issue? stuck open or closed?
injector issue?
sticking handbrake or caliper? causing drag

Thanks for the reply.

I may be wrong but I assumed that if it was an injector or egr problem it would throw a fault code??

I think you might have something with the sticky hand brake though, I felt like it stuck once. Might have a look into that

[borinous]

this is true i think i faulty EGR would throw a code. as if you bypass them without coding them out you get warnings.

Injectors i think can start to go bad without immediately throwing up codes. its only when the smooth running becomes out of scope does it put up errors. or at least thats my understanding on it. so i could be wrong.

If it feels like its being held back then it could be a sticky brake or hand brake.

Has the MPG always been low or has it suddenly dropped?

[Johnnybhoy7]

Originally Posted by borinous

this is true i think i faulty EGR would throw a code. as if you bypass them without coding them out you get warnings.

Injectors i think can start to go bad without immediately throwing up codes. its only when the smooth running becomes out of scope does it put up errors. or at least thats my understanding on it. so i could be wrong.

If it feels like its being held back then it could be a sticky brake or hand brake.

Has the MPG always been low or has it suddenly dropped?

I assumed they would throw codes but I'm not too sure that's why I've asked on here really.

It has been low for a while but I've twice replaced my main thermostat in the last year as it failed twice.

I can't really feel any resistance but when my cars been sitting overnight it definitely sticks and needs a little acceleration to pull away from the stickyness. Just assumed it was the hand brake shoes on way out never considered it could be holding me back so to speak

[Digitalize]

My 320D also gets around 40mpg at best now for some reason. I'm assuming it's worn injectors though.

[borinous]

well if you got no error codes im not sure what else it could be?

Mines remapped and on a 70-80mph cruise on the motorway easily returns over 50mpg. even with a duff thermostat it was still around 50mpg

[Johnnybhoy7]

Originally Posted by Digitalize

My 320D also gets around 40mpg at best now for some reason. I'm assuming it's worn injectors though.

Is there anyway of diagnosing the injectors? I think in my head I have already made the opiniOn it is the injectors. Slight puff of white smoke on start up

Originally Posted by borinous

well if you got no error codes im not sure what else it could be?

Mines remapped and on a 70-80mph cruise on the motorway easily returns over 50mpg. even with a duff thermostat it was still around 50mpg

I think it's gotta be the handbrake or the injectors

[Digitalize]

Not really without taking them out and testing, and even then if it's high mileage they're more likely worn than clogged, in which case they'll need to replaced or repaired. Looking at raound £200 for refurbished ones, each. Not sure on the cost of repairing your existing ones, but I can't imagine it's too cheap either.

It's this reason that I haven't really investigated any further, as it would take a long time for it to cost me £800 in extra fuel, and performance wise the car seems fine. It's a tad lumpy at start up to which can also be injectors, but might also for me be 2 failed glowplugs, which I will get done.

[Johnnybhoy7]

Originally Posted by Digitalize

Not really without taking them out and testing, and even then if it's high mileage they're more likely worn than clogged, in which case they'll need to replaced or repaired. Looking at raound £200 for refurbished ones, each. Not sure on the cost of repairing your existing ones, but I can't imagine it's too cheap either.

It's this reason that I haven't really investigated any further, as it would take a long time for it to cost me £800 in extra fuel, and performance wise the car seems fine. It's a tad lumpy at start up to which can also be injectors, but might also for me be 2 failed glowplugs, which I will get done.

Cars on just over 90k miles. Might try a bit of injector of injector cleaner see how that goes. As you say it'll be a while before its costs £800 worth of extra fuel

[Digitalize]

Ah I see, then maybe look at having them ultrasonically cleaned, think it's about £50 an injector. Mines on 194k.

[Johnnybhoy7]

Originally Posted by Digitalize

Ah I see, then maybe look at having them ultrasonically cleaned, think it's about £50 an injector. Mines on 194k.

http://www.halfords.com/motoring/eng...-engines-325ml

Think that would be worth a try? Only £6

[Digitalize]

Probably not no. Better off just buying premium fuel for 2/3 tanks and doing some spirited driving rather than just below 3k stuff to help clear it out.

When was it last serviced too?

[Johnnybhoy7]

Originally Posted by Digitalize

Probably not no. Better off just buying premium fuel for 2/3 tanks and doing some spirited driving rather than just below 3k stuff to help clear it out.

When was it last serviced too?

I only ever use premium fuel. Might give it a nice spirited drive

I service my car myself every August and February. Oil and filters, So only 5 months ago lol

[borinous]

Are you talking about the average MPG or the real-time swinging pendulum?

[Icekube]

i too am running a high mileage M47 320D (currently 210k)
when i first got it, i was getting high 30's, until i changed the Thermostats, and then i was getting 40-42. I don't have a motorway commute though, I'm on the A71 from Livingston to Edinburgh, so should be getting lower than normal.

if you had a binding brake, the wheel would be hot to the touch, so next time you finish a long journey, go around and touch each wheel to see if they are warm at all?

[borinous]

went out and looked at mine and according to the OBC im averaging 44.8MPG but on a steady cruise the pendulum needle is always over 50mpg

[Johnnybhoy7]

I was meaning the average on the OBC

I think the problem actually ratified itself regarding the brakes. I'm guessing something might have been stuck. I went a quick blast up the local duel carriageway with some harsh braking hoping the offending brake would head up a bit. After a few hard brakes I then accelerated and it seemed to unstick itself as my car absolutely shot away. All has been fine so far. Getting about 35mpg about town in airdrie. Lots or traffic lots of hills and lots of red lights so I'm pretty content with that. Thanks for all the help

[Aragorn30d]

it'll come back...

As craig mentioned above, touch each wheel after a drive and see if any of them are warm.

Craig had a sticking rear caliper that came and went. The cure was replacement.

[borinous]

you could reset the average so it starts fresh before you go on a long journey. that will then average that trip rather than for a months worth of town driving.

[chrissyw]

My 2006 E90 320d is on 120k.

EGR has been completely bypassed and mapped out. Service it every 8k. It's remapped by P-Torque and combined it's averaging about 45mpg a tank. My commute is a mixture of A roads, B roads and about 3 miles of stop start traffic.

My glow plugs are dead, still not got round to doing them yet.

I run Asda diesel and put millers injector cleaner in, every tank full so twice a month.

I noticed at idle when it was warm, the idle would go rough intermittently. Seems to have cured running the injector cleaner.

The OBD says I'm doing 40mpg.

Check your tyre pressure, mine was only doing 38mpg because I had 18 PSI in my rear tyres

[Johnnybhoy7]

Originally Posted by Aragorn30d

it'll come back...

As craig mentioned above, touch each wheel after a drive and see if any of them are warm.

Craig had a sticking rear caliper that came and went. The cure was replacement.

Once it starts sticking again I'll work out which one it is and service/replace it. I was out a 35 mile drive tonight and none of the wheels were hot so hopefully something was just stuck and it wasn't the caliper.

Originally Posted by borinous

you could reset the average so it starts fresh before you go on a long journey. that will then average that trip rather than for a months worth of town driving.

I've tried resetting it mate. Usually reset it everytime I put fuel in

Originally Posted by chrissyw

My 2006 E90 320d is on 120k.

EGR has been completely bypassed and mapped out. Service it every 8k. It's remapped by P-Torque and combined it's averaging about 45mpg a tank. My commute is a mixture of A roads, B roads and about 3 miles of stop start traffic.

My glow plugs are dead, still not got round to doing them yet.

I run Asda diesel and put millers injector cleaner in, every tank full so twice a month.

I noticed at idle when it was warm, the idle would go rough intermittently. Seems to have cured running the injector cleaner.

The OBD says I'm doing 40mpg.

Check your tyre pressure, mine was only doing 38mpg because I had 18 PSI in my rear tyres

I check my fluid levels and tyre pressure every second Sunday. I think it could have been a combination of a sticky caliper and injectors on the way out. Might try the millers injector cleaner and give it a good blast down the private road