What MPG should I expect from my TD5 Disco

[lyndon]

When looking it buy my new TD5 I was told by everyone to expect 28-30 mpg if I treat it right and keep my speed down. Especially on a long run. Now I drive to work on 2 A roads and a Motorway and probably 5 miles of B roads inbetween. I have been keeping to a constant 55 mph using the cruise control as much as possible. Its a 2.5 diesel manual vehicle and I have just calculated I am getting 22-23 mpg on average.

This seems a little excessive compared to what I was told to expect. What do others driving Diesel TD5's get to the gallon ?.

[thermidorthelobster]

That is a bit low.  Mine does about that but it's lifted, has big tyres and a hulking great roof rack.  I'd suggest you should be getting 26-28 in a manual.  Are you sure you're covering the distance you think you are?  If the mileometer's reading 10% low then you'll think you're getting 10% worse economy.

Are you getting smoke or anything that would indicate the MAF meter is faulty?  It might be worth getting it checked out by somebody who has Rovacom / Testbook and knows how to use it (ie, not a main dealer).

[andycwb]

That does sound low.   I get 23mpg with the normal lead boots, 26 if I'm careful.  That's on a 2004 (so Storm 2 engine) Auto Discovery.

[lyndon]

Miles shown are correct. The journey I have measured this on is one I know the mileage of. There is no smoke or anything to suggest there is a problem. The engine has only done 36,000 miles and is a 2004 fitted engine. A Landrover dealer suggested that there might be a fault code stuck in the ecu which hasn't been cleared and so is causing the engine to perform badly. Sounds like a clutch at straws to me.

[thermidorthelobster]

Get it plugged into a laptop and checked out.  But you do need to find somebody who knows what they're doing.

[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.

[lyndon]

Thanks for the info. Are these meters expensive?. If not it might be worth my while changing it anyway. Would it show up on the ECU as faulty as I am having it plugged into a diagnostic on Tuesday.

I thought the same regarding the compressor and I will be mentioning this to the dealer on Tuesday. The dealer is quite some way from me so I need to get all this right and sorted first time.

[thermidorthelobster]

They're not phenomenally expensive on the TD5 (compared to well over 400 quid on a 4.6) but I think they're something like £130, so not worth replacing unnecessarily.  But check because I might be way out.

If the diagnostics user knows what they're looking at, they'll be able to check out the MAF meter.  But you DO need to know what you're looking at.  Take it to a main dealer and if it's not in the manual they won't have a scooby.  It won't necessarily flag up a fault code if it's still sending some sort of sane output;  that's why you need somebody who knows what the MAF should be showing in different circumstances and can spot when the output's different from what you'd expect.

[lyndon]

Sounds like a pain in the rear then. I wonder if this would be covered by my warranty.

[lyndon]

Ayone got a TD5 local to Basingstoke area thats okay on economy willing to change MAF Meters for a week to help me out ?

[thermidorthelobster]

Either that or you could find somebody with Rovacom who knows how to use it and could compare your truck to their own.  AndyCWB might be up and running with his, and he's in Sandhurst.  Somebody might be amenable to checking it out in exchange for beer tokens;  IIRC there are a couple of other people in this area with Rovacom too.

[lyndon]

Thanks. Anyone within reasonable distance of Basingstoke with a Ravacom willing to check it out for me. Crate of beers ion it for you ??

[andycwb]

I haven't got around to upgrading my Rovacom to do the Td5 yet, or I'd be happy to help out.  I want to sell the existing one (P38A modules) first, so it'll be another couple of weeks, I'm afraid.

Nick Kerner 4 wheel drive, between Bracknell and Windsor aren't that far away and have a Rovacom Pro and should be able to help out.  Give them a call and see if they can help.

I have another theory about this poor performance issue, which is that there are different fuel maps out there, and the engine may have the wrong one.  Without plugging the Ro

[lyndon]

How would I or the chap thats looking know if the wrong map is installed ?. I need to find all these things out as I am hoping to get my local garage to have a look. They have the kit, they think they have the software for the TD5 so we are going to try on Tues before I ring the dealer so I can at least inform him what needs doing.

I took the air filter apart earlier. It was filthy. I intend to get a new one next week, but I have cleaned the old one up for now. Don't know how much effect that could have on performance.

[andycwb]

Bung me a PM with your e-mail address and/or phone number.

Some things to check.  

0) Any fault codes being reported, even if they're showing as "not currently present"
1) Fuel Tune map ID code
2) Programming History, if any.
3) AFM values at idle and under load (i.e., booting it down a fast road).

If you can mail me the results of these I'll see what I can come up with.

Andy

[lyndon]

You have a PM

[mike142sl]

Lyndon,

I've had a similar concern, although mine is Auto. A couple of weekends ago I could hear a chirping noise that I thought was birds in the trees, but after hearing the same birds after each junction I started to think its coming from the Disco??? Turns out the brakes were sticking, so I was driving with some of the brakes on !!!! - main dealer adjusted them (whoever fitted them didn't use copper grease or something) and they also cleaned the car, then didn't charge a penny  :shock: - gobsmacked

Just letting you know incase you have a similar prob with your brakes. Issues like this can often be down to a really simple solution.

All the best

[Cal]

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

That's been said a few times on the VW forums I've been on - Golfs and Boras seem to have a lot of problems with MAF sensors in general, but many people have gone through them faster with aftermarket oiled filters - apparently the oil covers the MAF sensor and messes it up.

Might be worth giving it a clean by spraying carb cleaner on it.

The guys on the VW forums just consider the MAF as a service item now like I guess a lot of D2 owners think of the air bags on their rear sus.

[lyndon]

The vehicle has gone back to the dealer for repairs to be completed. the list goes like the -

1 Sump, Rear main gearbox, Transmission and rear dif oil seals

2 Rear air bag suspension fault. Keeps going down when static, but only sometimes.

3 Leaking front sunroof. I removed the head lining and the drain pipe has sheared away from the sunroof assembly.

4 Poor MPG required putting on a diagnostic.

So far they've had the car for 10 days and have replaced 7 oil seals and the rear air bags. They are starting on the sunroof and MPG today. Bill so far £2000 and not a penny to be paid by me.