B

bonnybrook

Active Member
Been asked before but can't help thinking something not quite right with my TD4 auto.

Getting about 25-26 mainly local B roads and only 30ish on a motorway run 70+ . Official combined it's 32 so I would expect it to be much better on a run. I'm sure it used to do more.

Car runs fine so not sure what to look for. Cleaned ERG other day but no noticable improvement.

Could this be the MAF? I have a failing PAS pump (next job to change) not sure if this could be impacting on it.

Any ideas or is this fairly normal?
 
bonnybrook said:
Been asked before but can't help thinking something not quite right with my TD4 auto.

Getting about 25-26 mainly local B roads and only 30ish on a motorway run 70+ . Official combined it's 32 so I would expect it to be much better on a run. I'm sure it used to do more.

Car runs fine so not sure what to look for. Cleaned ERG other day but no noticable improvement.

Could this be the MAF? I have a failing PAS pump (next job to change) not sure if this could be impacting on it.

Any ideas or is this fairly normal?
Click to expand...
disconnect egr.......try injector cleaner?.....wos the mileage, could be MAF......:confused:
 
Sounds a little low to me.
First thing is to make sure your cars filters are renewed including the important crankcase breather filter/valve assembly. As for the egr valve, the least said about it the better. Disconnect the small vacuum pipe off the front & plug the pipe with a greased tight fitting bolt to disable the egr till you can sort out a bypass asap (available through ebay). Use Millers Powersport 4 diesel additive every time you fill up. A bottle costs around £10 & will last you for 3 - 4 thousand miles. It takes around 250 miles to start working but cleans out the injection system & boosts the fuel cetane value. It might be worth not changing the fuel filter till you've run about 500 miles with the Millers as it will clean everything out including the tank.

When I first got my Td4 Auto it did 30 - 31mpg in & out to work (half & half mixture of motorway & town driving) & 39mpg on a run.
After servicing & egr bypass it went up to 32mpg.
Next after 250 miles using Millers it went up to 35mpg (at this rate the millers more than pays for itself).
I then added a roverron chip for power which saw a slight reduction in economy back to 34mpg & over 40mpg on a run. Even around town only, it still returns around 30mpg.

The Millers & the egr bypass are very easy mods which do have a positive effect on fuel economy as well as improved performance. Don't bother with chipping though if you're happy with performance & are only interested in improved economy.
 
Done 75K. Changed breather few weeks ago. Put injector cleaner in for the last two tanks thinking that might help but doesn't seem to have made a difference. Haven't tried disconnecting the ERG yet but will - I cleaned out the ERG last week but no diff.

Considering a Roverron MF75p with MAF but not sure this will make a difference if my MAF is ok.
 
nigel8 said:
disconnect egr.......try injector cleaner?.....wos the mileage, could be MAF......:confused:
Click to expand...


Maf's a fair point. I use a roverron mafam compensator on mine but the quick test on how bad yours is, is to disconnect it & take the car out for a quick test drive. If your car pulls from low revs like it's never done before then your Maf is faulty. If the improvement is very slight or not noticeable then your Maf isn't badly out & won't be your immediate problem.
 
thanks guys will try the MAF disconnect next chance I get. Didn't really wan't to spent £100 on MF75 and MAF if it's really not bad. Performance is good generally, although the auto doesn't change up as quick as I would like about 40-50MPH and "hunts" a bit.

More concerned about the motorway MPG than local runs at 25-26 don't seem to bad - lot of 15 min runs. I don't seem to see a huge improvement on a run. I recall I was getting out 34 on a run last summer - but that was taking it really easy.

Full service in May, IRD, coolant, engine. Cleaned EGR, new engine breather and injector cleaner in last few weeks.

Only gear box oil and the failing power steering pump not sorted - not sure these could impact much.
 
chromiumuk said:
Sounds a little low to me.
First thing is to make sure your cars filters are renewed including the important crankcase breather filter/valve assembly. As for the egr valve, the least said about it the better. Disconnect the small vacuum pipe off the front & plug the pipe with a greased tight fitting bolt to disable the egr till you can sort out a bypass asap (available through ebay). Use Millers Powersport 4 diesel additive every time you fill up. A bottle costs around £10 & will last you for 3 - 4 thousand miles. It takes around 250 miles to start working but cleans out the injection system & boosts the fuel cetane value. It might be worth not changing the fuel filter till you've run about 500 miles with the Millers as it will clean everything out including the tank.

When I first got my Td4 Auto it did 30 - 31mpg in & out to work (half & half mixture of motorway & town driving) & 39mpg on a run.
After servicing & egr bypass it went up to 32mpg.
Next after 250 miles using Millers it went up to 35mpg (at this rate the millers more than pays for itself).
I then added a roverron chip for power which saw a slight reduction in economy back to 34mpg & over 40mpg on a run. Even around town only, it still returns around 30mpg.

The Millers & the egr bypass are very easy mods which do have a positive effect on fuel economy as well as improved performance. Don't bother with chipping though if you're happy with performance & are only interested in improved economy.
Click to expand...


Been on me jollies so only just got round to looking at this again. I've bought some Millers 4, done about 100 miles so far but too early to tell on MPG. Good news is diesel now 10p cheaper than before my hols! Will also do the erg mod - do I simply pull the small tube off the erg? Does it need blocking up at either end?

Got my mechanic to pop on the new Power steering pump whilst I was away so see if that has any impact.
 
bonnybrook said:
Been on me jollies so only just got round to looking at this again. I've bought some Millers 4, done about 100 miles so far but too early to tell on MPG. Good news is diesel now 10p cheaper than before my hols! Will also do the erg mod - do I simply pull the small tube off the erg? Does it need blocking up at either end?

Got my mechanic to pop on the new Power steering pump whilst I was away so see if that has any impact.
Click to expand...


You need to block up the rubber pipe as the vacuum is also required for the turbo vanes apparently. I used a tight fitting bolt greased up & pushed fully home. Just leave the valve end open as it's now redundant. You should seriously consider the egr bypass though as you'll only get a small amount of benefit by disabling the existing unit. The Millers can take up to 250 miles before it starts to work properly.
 
Done about 100 miles using the Millers so far. No real benefit on the MPG so far - about 25 local - a lot of short journeys and left idling a bit. Looking at urban official this is about right actually but never seen the 37 they say extra urban. I will report back when i've managed a motorway run and done the ERG.

Can report however that the Millers 4 seems to make a big difference in the feel, performance and running when cold. Thanks for the tip!
 
Bollocks...bollocks.....bollocks


Unless your speedo is correctly calibrated to the tyre size your running (original setups are typically 8-12% below) then you dont really have a clue what MPG your getting.

Im running on 215/80/15s which when new will give a nearly accurate reading, but can still lose a few % due to wear....
 
Latest MPG. Ran the Millers 4 for a total of 350 miles now.

Last 40 quid (107p) got be just over 230 before light came on. Thats 28MPG - all local runs except 20ish motor way. So getting better. Going on a long run Sun so will see what shes getting on the motorway.
 
How do you check your MPG?
You need to brim the tank, then brim it again and check the mileage, preferably over at least 1000 miles to compensate for slight differences in pump cut-offs or slopes in the filling station.
Working on when the light comes on will be very vague. I've know the light come on, parked, then on restarting done several miles before it came on again, so it's hardly an accurate measure.
Oh, and in the 95000 and 4 1/2 years since I got mine, its stayed a whisker under 30mpg, hammered across the Welsh Mountains or along duel carriageways at speeds couldn't admit to. Gentle driving on holiday sees about 35
 
I'm putting £30-40 in and working out total amount of fuel/miles. Usually run 10-15 miles with the light on to even that problem out. Measure distance using the trip function.

Did a run upto York yesterday, stayed at 65-70 all the way (painful) - still not used the 30 quid i put in yet. Currently stands at 170 miles on that from well into the red with a bit left.

If I get 200 miles thats 32 MPG, 150 motorway/A roads and rest local - not brilliant I must admit.

I'm sure the best i've had on a run is 34 and that was slip streaming behind a wagon at 60!

Will let you know the outcome.

Useful calc tool here -

Fuel Calculators » Fuel-Economy.co.uk
 
It really isn't a good idea to keep running down untill the fuel light comes on. Just laying up future fuelling problems from potential pump cavitation and/or sludge.

MPG checks are best done from full tank to 1/4 and then refilled to same full point.

I kept strict records for a while on my TD4 Auto and got the following:-

Urban - 20 miles each day to and from work - 28mpg
Extra Urban = some motorway - 30 to 32 mpg
Long Motorway Runs at Max speed (ish) :rolleyes: - 37 to 40mpg

And, just for the hell of it :-
A long (boring) motorway run at no more than 60mph gave 45mpg

I then started using Millers additive and have so far found an approximate 5% increase in these figures across the range of driving types.

The distances are fairly accurate against my SatNav GPS to a point where the difference is negligable - although I have noticed a 10% error on the speedo against the SatNav for actual indicated speed travelled. Speedo overeads - so I should keep my license :D
 
Agree - I don't want a knackered pump as well.

Begining to think I have the wrost mpg of any TD4 auto! Stuggling to get just over 30-32 on a steady motorway run can't be right.

I've cleaned ERG, running Millers 4.

Wondering if this could be the MAF?

(ps agree on speedo - mines about 5mph out vs sat nav)
 
bonnybrook said:
Agree - I don't want a knackered pump as well.

Begining to think I have the wrost mpg of any TD4 auto! Stuggling to get just over 30-32 on a steady motorway run can't be right.

I've cleaned ERG, running Millers 4.

Wondering if this could be the MAF?

(ps agree on speedo - mines about 5mph out vs sat nav)
Click to expand...

I don't think you're alone here - mine's not that great either and I do notice it gets progressively worse as the weather gets colder - could be down to increased load on the engine from fan/window demister and FBH.
I keep mine well serviced and tend to get around the 28-30 mark for my trip to work runs (mainly A & B roads averaging about 40mph).
Oh by the way I've got a Roverron synergy and pierburgh MAF - not sure if that has made any diff to the mpg - but the car sure runs better!
 
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