Vehicle & Technical > Discovery

What MPG should I expect from my TD5 Disco

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Daz800:
When doing 70 (no more) we get 32
Around town 25-28

No mods just a box standard manual td5 (gs7).

Darryl

lyndon:
That means I've got a problem. If cruising at 55 I am getting 22-23 mpg. What could be causing such poor MPG. Like I say its a new engine and sounds and  drives fine. Tyre pressures are fine, she is near to her next service date, but still thats a massive drop in MPG.

Any ideas ?.

Tuesday I will be speaking to the dealer I bought it off. Rear Suspension air bag leak, Oli leaks on sump, gear box and rear diff, all of which they agreed to sort out ( it appears they have cleaned up the areas and made it look like they have repaired them. suspiciously too clean if you get my drift, but still dripping on my nice clean driveway) and now poor MPG.  Might have to start down the line of unfit for purpose. See if that motivates them. Going to get it inspected by an independant, get a list of jobs required and then present the dealer with it.

thermidorthelobster:
Poor economy seems to be a fairly common problem on TD5s;  I've heard of several people whose economy is in the low 20s, or has suddenly fallen to the low 20s, but I've not yet seen any pattern in what causes it.  The MAF meter, if faulty, may affect the economy (because of overfuelling);  I'm on my third at the moment.  But I strongly suspect there is something else going on in some of them, but I've not worked out what it is yet.

lyndon:
Sorry, I am not very mechanically minded. Big disadvantage for a landrover owner I know. What is a MAF meter, where is it and what does it do?.

Also if my rear airbag is leaking this is going to mean the air compressor is runninig to compensate all the time. Could this be the cause of increased fuel useage ?.

thermidorthelobster:
The Air Mass Flow meter (not sure why it's MAF and not AMF) detects how much air is coming into the air intake, and feeds this info to the ECU which works out how much fuel to mix with it.  This means that the engine mixes the optimum amount of fuel and can adjust to different air flow rates, caused by speed, air intake restrictions, snorkels, altitude, atmospheric air pressure, moisture content, etc.

The MAF in a TD5 outputs a number (ranging from 4-50 or something like that, I can't remember exactly) which the ECU looks at.  Some meters naturally read higher or lower than others;  some fail and give fairly random outputs.  My last one stuck at 8 and never changed.

The MAF meter is in the air intake path just downstream of the air box.  It's connected by a multiplug and to change it you unplug it and just take that section of the air intake out.  If you know somebody else with a TD5, you can swap it in about 2 minutes.  Might be worth trying out and seeing if your economy gets better and theirs gets worse.  I think it's the same part with Defenders and Discos;  if it's not, they're still interchangeable.

I think there's a link between MAF failures and K&N-style oiled air filters, but I can't prove this.  I've had 3 MAF failures on 2 different vehicles after I installed a K&N filter.

I don't think your compressor running constantly will affect your MPG by any noticeable amount, but it WILL knacker your compressor.

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