MPG problem

[depresion]

I'm struggling at the moment to get my MPG into the 50s the way I used to all the time, the only symptom I can find is the low MPG as the car still pulls incredibly well, there are no odd sounds from the engine, gearbox, clutch or anywhere else (well from the radio but I like prog rock). There is no sign of any binding at each corner and the tyre pressures are fine.

Under hard acceleration the instant MPG counter says about what you would expect but it's at light throttle (yes I know it doesn't have one but you know what I'm saying) that the readings are lower than I expect, it's defiantly not just the display that's out as I'm barely getting 400 miles from a tank.

 

[Husbandofstinky]

Is it worth doing a reset and an old fashioned mpg check?

 

[Ibiza Dan]

I have similar mods to you and i get about 37mpg when doing city driving (stop start)

 

[depresion]

I could never live with 37mpg I got that from my last petrol.

 

[Husbandofstinky]

I've never acheived that an mpg figure that low before. The car gets 47mpg to and from work (7 mile countryside/town conditions). Not exactly town stop start but not too far off it. Also 55mpg on a 75mph motorway/dc run.

To get 37mpg I would have to be really nasty. Usually get nigh on 500 miles on a tank full locally.

Still reckon a reset and an old fashioned calculation just to double check. Filters? (I know you said it was running right).

 

[depresion]

Excel is saying 46mpg from the last tank (I don't vent) so the MPG counter is normally a little optimistic showing an average of ~55 when Excel says 53 something. Now they are both showing ~46 so the real drop is less than the trip computer drop but I'm taking it down to a local independent tomorrow and I'll stick it on the fault code reader see if anything pops up.

 

[Ibiza Dan]

Yeah i bought the car not long ago and compared to my last petrol its very good on juice to be honest.
Im gonna calculate myself just to make sure
But i reset it when i bought it and its normaly on about 37 when i bother looking.
So i take it thats the average the car has done since i reset it ???

 

[ChrisGTL]

Mine has also taken a hit recently.

I've kinda given up on it now, my MPG dropped when I had a mufflerectomy but have been assured this is not the cause, and plenty people on here have this mod and seen no drop in MPG.

So I replaced all the engine oil, cleaned air filter, installed new fuel filter. The 1st tank full after that gave me an increase of 80-100miles on that one tank, but its now back down 80-100miles.

I can just about achieve 450miles on a full (not-vented) tank.

I did have my car up on jacks the other week to put my SFS hoses on, noticed the front wheels seem very noisy when I spun them by hand, and they pretty much stopped still once I had let go.

Wheel bearings?

 

[Ibiza Dan]

maybe bearings or brakes binding slightly ?

 

[westoncraig]

i average about 450 on an unmodded 150tdi... i think thats ok

 

[Husbandofstinky]

Sounds like brakes to me Chris. You should hear if the bearings are going. Just a case of take off pads, clean everything up and copper ease back again.

I have to do this on the Accord once a year (apparently Honda's a renowned for sticky calipers). I don't know if Stinky's Civic will suffer from it but thats all main agent stuff/warranty.

I assume discs are not warped either.

 

[oldman]

i avg 550 on an unmodded 150tdi

sensible driving around town and commuting i get 48ish and 80-95 on private roads i get 45-50. occasionally get 52 when do real miss daisy driving but that does my nut in too much

only ever done a single reset in 2yrs ownership and did make diff in feel for a bit but now i'm back to normal sensible driving

not really answer but gives you another variartion.

i do drive a leon mind not the ibiza

 

[Ibiza Dan]

I think this post is really good because loads of people seem to say they get this amazing mpg but alot of it i dont think is possible unless you really never went over about 2k revs.
I dont rag it everywhere but ive got a performance car for a reason if you know what i mean and its good to see what other people get.
Maybe we could compile a data base or list of some sort so people can compare what MPG they get with certain mods.

Thanks
Dan

 

[Husbandofstinky]

I think this post is really good because loads of people seem to say they get this amazing mpg but alot of it i dont think is possible unless you really never went over about 2k revs.
I dont rag it everywhere but ive got a performance car for a reason if you know what i mean and its good to see what other people get.
Maybe we could compile a data base or list of some sort so people can compare what MPG they get with certain mods.

Thanks
Dan

I don't think if you stayed under 2k revs all the time it'll do the engine any good let alone clog up the turbo. I don't and I assume that the other members on here don't either. It'll get 90% normal driving and possibly 10% spirited.

Unfortunately the Leon is not exactly a 'performance' car more of a reasonably quick hatch.

If you're getting under 40 all the time then there is either a problem or you're crucifying your motor.

 

[Clone]

My breaks do the same i think going to clean them next week!

Also i think you will be hard pushed to get over 400 from an ibiza. I've only done it once on my 130 got 440 mostly all motorway miles.

 

[ChrisGTL]

Sounds like brakes to me Chris. You should hear if the bearings are going. Just a case of take off pads, clean everything up and copper ease back again.

I have to do this on the Accord once a year (apparently Honda's a renowned for sticky calipers). I don't know if Stinky's Civic will suffer from it but thats all main agent stuff/warranty.

I assume discs are not warped either.

Defo not warped. But sticking, sounds like a plan stan!

My car does seem to slow itself down quickly when freewheeling, even on a slight downhill.

I'll strip them down this weekend, clean them up and apply polycop

 

[Husbandofstinky]

I've known the Accord not to roll back on a noticable incline before! Serviced brakes and mpg instantly up by about 4. Still not high enough to use it regularly though!

Good luck with it. I hope that's all it is (i.e. sticky caliper piston) I'm sure it is.

 

[the_fbi]

Interesting read, as I was about to start a thread about mine but I won't so all the info is kept in one thread.

Monday 1st Sept I did an round trip (110 miles) to a customer which I'd not been to before, mostly motorway at circa 68mph and got 68.8mpg, which is my normal long distance motoroway journey mpg.

Since I filled up on Tuesday I've been an easy 10mpg down on my normal to/from work journey which is 53 miles each way. I'd normally see 61mpg to work and 65mpg to home.

I'm struggling to get within 10mpg of those figures and my driving style is unchanged.

Tyres/brakes/etc is all unchanged, all I did was fill up with fuel. I'm on my 2nd tank since and still the same issue.

Performance is unchanged at low speed, not sure if its quite as quick picking up in 6th from 60+ as it normally is, cruise mpg appears unchanged too, but under load the instant mpg is way less than it normally is.

Its not wind/drag induced either.

All I can think of, apart from a dodgy batch of fuel, is the variable vane mechanism getting stuck/broken. I gave it a little flick tonight before coming home and need to investigate further as there wasn't any resistance, so not sure if the link between actuator and turbo vane is broken.

Fuel is from Sainsbury's and has been for the past 12k.

 

[ChrisGTL]

Interesting read, as I was about to start a thread about mine but I won't so all the info is kept in one thread.

Monday 1st Sept I did an round trip (110 miles) to a customer which I'd not been to before, mostly motorway at circa 68mph and got 68.8mpg, which is my normal long distance motoroway journey mpg.

Since I filled up on Tuesday I've been an easy 10mpg down on my normal to/from work journey which is 53 miles each way. I'd normally see 61mpg to work and 65mpg to home.

I'm struggling to get within 10mpg of those figures and my driving style is unchanged.

Tyres/brakes/etc is all unchanged, all I did was fill up with fuel. I'm on my 2nd tank since and still the same issue.

Performance is unchanged at low speed, not sure if its quite as quick picking up in 6th from 60+ as it normally is, cruise mpg appears unchanged too, but under load the instant mpg is way less than it normally is.

Its not wind/drag induced either.

All I can think of, apart from a dodgy batch of fuel, is the variable vane mechanism getting stuck/broken. I gave it a little flick tonight before coming home and need to investigate further as there wasn't any resistance, so not sure if the link between actuator and turbo vane is broken.

Fuel is from Sainsbury's and has been for the past 12k.

Keep us updated.

 

[the_fbi]

Plugged in VAG-COM last night, same 3 errors I always have.

Fuel sender Intermittant short to B+ (forget the code)
00779 - Outside Air Temp. Sensor
01086 - Speedo Vehicle Speed Sensor

Always have these 3, although not sure how the speedo one gets implicated. The first two are to do with the instrument panel and reading 0 fuel then losing the outside temp on dash and aircon.

VSS works fine for dash and stereo, so should be giving the correct info to the fuel computer for mpg calculations.

Actual fuel used too (ie. fuel put in when filling up) matches what's being reported by the computer too, so its not duff info from the VSS causing it.

Forgot to mention I applied some dielectric grease to the MAF connector at the weekend to see if that helped. It didn't.