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        General >> Problems >> 1998 TDI with MPG problem
        
(Message started by: redarrow007 on Apr 22^nd, 2010, 11:33pm)

Title: 1998 TDI with MPG problem
Post by redarrow007 on Apr 22^nd, 2010, 11:33pm

folks out there can you help me, i have a 98 TDi estate that only does 24mpg. i checked out the OBD and cannot find any problem, the car runs OK with no problems. so i cant find any faults. any ideas as to what to look for as its costing me more than my volvo 940 to run....cheers

Title: Re: 1998 TDI with MPG problem
Post by tonyboy on Apr 23^rd, 2010, 12:05am

Fuel leak somwhere.......... maybe.........

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on Apr 23^rd, 2010, 12:06am

no not a fuel leak, i dont think ive checked the fuel lines....thanks

Title: Re: 1998 TDI with MPG problem
Post by amigafan2003 on Apr 23^rd, 2010, 9:38am

24mpg driving where? If it's a town car then that's probably about right. If it spends most of the time on the motorway @ 70mph then you're correct, something is amiss.

Title: Re: 1998 TDI with MPG problem
Post by Highlander on Apr 23^rd, 2010, 10:12am

Brakes binding?
tyre pressures?
Thermostat ok?

dirty injectors, EGR, air filter etc can all have a major effect on mpg

Is it an auto?

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on Apr 24^th, 2010, 12:15pm

thanks for the replys.. checked brakes and stat and most of the norm,,,the only thing i can think of is the injectors. the mpg is similar in town and on m/ways

Title: Re: 1998 TDI with MPG problem
Post by Mike H on Apr 25^th, 2010, 2:37pm

What mpg should a diesel normally do?

Title: Re: 1998 TDI with MPG problem
Post by Robzere31 on Apr 25^th, 2010, 5:21pm

on 04/25/10 at 14:37:45, Mike H wrote:

What mpg should a diesel normally do?

I tend to get around 35-40 mpg out of mine. Average around 420-450 miles out of a tank.
205K on the clock, although it's had new injectors recently.

If driven like a grandad on the motorway 40 mpg is easy to achieve, giving it a bootful though drops it to around 35mpg. lol

How are you working out your MPG? tank to tank?

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on Apr 26^th, 2010, 1:34am

yes tank to tank,,,,

Title: Re: 1998 TDI with MPG problem
Post by Mike H on Apr 26^th, 2010, 8:18pm

Interesting...

Title: Re: 1998 TDI with MPG problem
Post by tonyboy on Apr 26^th, 2010, 8:46pm

Maybe filling the tank up to full, then refill when it's nearly empty, and so on then you get miles per tank.........

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on Apr 27^th, 2010, 1:27pm

thats what ive been doing tony....

Title: Re: 1998 TDI with MPG problem
Post by Mike H on Apr 27^th, 2010, 1:31pm

Can be a problem with accuracy for instance if you drive 'til the low fuel indicator comes on, but then how much "reserve" is there? Doesn't mean you've used the whole 70 litres

I've done it using partial filling, IIRC how it goes is you arrive at filling station, make a note where the fuel gauge needle is. Put in X number of litres, a round number, and make a note of it. Zero the trip.

Drive until fuel gauge reads same as before, and make note of miles from trip. Voila. You now know how many litres covered how many miles.

To convert litres to gallons divide by 4.55

It assumes of course the speedo and trip meter are accurate

Title: Re: 1998 TDI with MPG problem
Post by Highlander on Apr 27^th, 2010, 9:14pm

I wouldnt go by the gauge Mike.

best way is to fill the tank, reset the trip, then once its nearly empty refill it and note how much fuel it takes, which is what Redarrow has done.

bear in mind the trip meter shows around 10% less than the distance actually covered.

eg if the trip shows 50 you have done 55 miles

this alone wouldnt account for Redarrows low mpg though, there must be something else affecting it

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on Apr 27^th, 2010, 10:37pm

thank chaps, ive assumed the trip is 100% spot on ive got 3 programs on my iphonne for cac the MPG. all are set for UK miles per gallon, with liters input. all 3 programs say around 24 per gallon. i went up to scotland in nov last year and found it was doing 25mpg on the motorway home that was at 80mph none stop.

Title: Re: 1998 TDI with MPG problem
Post by Mike H on Apr 28^th, 2010, 12:19pm

It does seem rather rediculous, I mean the 2 litre petrol should do at least 30 mpg cruising like that so what's the point having a diesel! Albeit 2.5 L (?)

I think the formula is IIRC:

mpg = miles / (litres / 4.55)

Title: Re: 1998 TDI with MPG problem
Post by Mike H on Apr 28^th, 2010, 12:22pm

A more accurate constant for the litres conversion is 4.54609

Title: Re: 1998 TDI with MPG problem
Post by Highlander on Apr 29^th, 2010, 7:02pm

Is it an auto?

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on May 4^th, 2010, 10:54am

yes its a big old auto

Title: Re: 1998 TDI with MPG problem
Post by Highlander on May 4^th, 2010, 12:16pm

Ahhh thats helps...

whats your RPM at 70 mph?

It may be running in the wrong gear or has a faulty torque convertor

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on May 6^th, 2010, 1:22am

you know ive just been to dublin and back and dinnt look that much, it is what i think as quite low, i will check it out tommorow cheers

Title: Re: 1998 TDI with MPG problem
Post by Mike H on May 6^th, 2010, 2:44pm

Something like 3,000-ish with overdrive engaged? @ 70....

If so that's normal

Title: Re: 1998 TDI with MPG problem
Post by gozz on May 6^th, 2010, 3:22pm

Diesel versions have the highest diff ratio Mike,wouldn't think 3000 rpm.
GOZZ

Title: Re: 1998 TDI with MPG problem
Post by Mike H on May 7^th, 2010, 11:32am

Two and a half then? ;D

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on May 7^th, 2010, 1:58pm

acording to my speedo at 70 im doing 2400 revs, i will calc my last dublin trip and let you know.cheers

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on May 7^th, 2010, 2:30pm

just done some calcs. ive done 410 miles on 65.29 liters of fuel, by my rec thats 28mpg much better dont know whats happend better than normal.

Title: Re: 1998 TDI with MPG problem
Post by Mike H on May 8^th, 2010, 10:07am

I agree I'm making it 28.5

I'm guessing it's not all motorway type roads though?

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on May 8^th, 2010, 2:15pm

no that was motoway all the way at 80mph

Title: Re: 1998 TDI with MPG problem
Post by Mike H on May 8^th, 2010, 7:01pm

Fairy nuff, but still in that case would've thought for a diesel could do better (?). What does Highlander reckon, he's using a diesel at the mo I think

Title: Re: 1998 TDI with MPG problem
Post by Highlander on May 10^th, 2010, 4:46pm

Never really seen an auto but the manual should be getting 35/40 mpg depending how you drive it on the motorway.

I assume the auto will get a bit less but shouldnt be that much

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on May 10^th, 2010, 10:06pm

ive got to fill it up tomorow from 1/2 a tank so il let you know how i go cheers.
Just to let you know the diesel autos are ment to be crap at towing, i tow a vey large box trailer with mine for the last 12 months.
all i do when im on the m way is put it in 3rd gear as it stuggels a bit in fouth but other than that its great for towing.
the MPG when towing is about 21mpg not good but good for work

Title: Re: 1998 TDI with MPG problem
Post by Mike H on May 11^th, 2010, 9:30am

Interestingly, I have noticed in the past Scorpios have been quite popular with campers, mainly I expect cos you can fold the back seats flat and heave loads of gear in the back.

Also interestingly, the last one I saw on site with a caravan was a 2.3 Ultima saloon, petrol, not diesel.

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on May 12^th, 2010, 7:48pm

acording to most the diesel autos are rubbish at towing i have no problems with mine as long as the tyre presures are ok on the rear and i dont use fouth gear.

Title: Re: 1998 TDI with MPG problem
Post by Mike H on May 31^st, 2010, 11:56am

on 04/25/10 at 17:21:05, Robzere31 wrote:

I tend to get around 35-40 mpg out of mine.

If driven like a grandad on the motorway 40 mpg is easy to achieve, giving it a bootful though drops it to around 35mpg. lol

Faffi put up some review links, for the What Car one

http://www.whatcar.com/car-reviews/used/ford/scorpio-saloon/full-review/24766-2#tabsection1

They also reckon 35 mpg for the diesel (under What are running costs)

According to my owner's handbook it is indeed about >=36 mpg for a constant 75 mph, slightly worse for the estate. Doesn't list auto version (weren't making them yet I presume) but can suppose knock another couple of mpg off, going by the other autos in the list

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on Jun 1^st, 2010, 2:34pm

thanks mike

Title: Re: 1998 TDI with MPG problem
Post by Mike H on Jun 1^st, 2010, 6:06pm

I'm guessing that mostly the original idea for having the diesel was 'cause the fuel was cheaper than petrol. (?)

Title: Re: 1998 TDI with MPG problem
Post by redarrow007 on Jun 2^nd, 2010, 4:02pm

that was plan A.......due its MOT in two weeks, if it passes OK may have the injectors looked at

Title: Re: 1998 TDI with MPG problem
Post by Mike H on Jun 2^nd, 2010, 6:41pm

Yes somewhere else I quoted from somewhere maybe injectors need cleaning or replacing >60k if too much exhaust smoke I think