I'd appreciate some advice from you technical folks... MPG in my vRS (ASZ) has recently dropped significantly, especially on longer, faster runs. I was getting about 47 mpg before (which I thought was a bit disappointing) but now it's more like 43, or about 40-50 miles less from a tank. My driving style and journeys haven't changed, so what's happened?

I've not really noticed any other change with the car, perhaps a bit less power and/or a bit less responsive, but that could just be in my head. I think perhaps it is putting a little more smoke out under hard acceleration (even on Millers), which I am lead to believe would be caused by a boost leak. However my turbo piping looks the same as ever (thin film of oil around the joint in the bottom of the intercooler, but that's always been there), and I've not noticed the turbo being any louder. Recently it's had an MOT, new tyres on the front (yes the tyres are inflated correctly, and they're the same ones it had on it before) and a new air filter (OEM paper, fitted by me), and I'm wondering if the MOT diesel smoke test could have exasperated a boost leak :-S

Aside from a boost leak is there anything else that could give the above symptoms, could the MAF give me similar problems? Would a boost leak or MAF problem turn up on a VAGCOM scan? Is there anyway for me to test for boost leaks, and if that is the problem, what's the fix and how much a I'm looking at? I'm not very competent mechanically, so will probably end up having a local garage fix it up, whatever the problem is.

Gonna be putting quite a few miles on it next weekend, so I'd like to patch it up before then otherwise the trip is going to be more expensive than I bargained for! Thanks in advance for your help.

Edited 9 September, 201213 yr by ckyliu

New air filter fitted, then try this DIY tuning method, it costs nothing apart from a little fuel.

http://www.briskoda.net/forums/topic/244178-simple-cheap-diy-tune-up-brilliant/

DB.

Have you tried disconnecting the MAF sensor and driving it a couple of miles. If it drives the same as it always has then your MAF is at fault. Poorly MAF's lead to poor MPG's.

Have just had this on my car and one of the boost pipes had come loose. Hadn't come all the way off but slipped at the bottom.

Symptoms were as you described, mpg down about 15%, lots of smoke but no significant loss in power.

Would a maf fault cause smoke? I only get 42mpg average!

I only get 42mpg average!

I've seen how you drive!

Well, that doesnt help but even when i drive like grandad like yourself it doesnt get any higher!

New air filter fitted, then try this DIY tuning method, it costs nothing apart from a little fuel. http://www.briskoda....e-up-brilliant/

Curiously I was thinking of disconnecting the battery to force an ECU reset, so I will give this a go on my day off tomorrow and see if it sorts it out. If not looks like a trip to the local indie in the afternoon to see what he can make of it, if it turns out it is a boost leak I've no idea how to fix it or even gain access.

Edited 9 September, 201213 yr by ckyliu

I've now been told it could be the EGR or the fuel filter as well. I tried the battery thing, doesn't seem to have delivered any gains.

So it's booked in at my local indie on Thursday to see if they can work it out.

Edited 10 September, 201213 yr by ckyliu

Any result on this?

Inspected turbo pipes, they seem okay; bit of an oily film around the join at the bottom of the intercooler and one of the joins up in the top of the engine bay but nothing you'd call exceptional. Pipes seem a loose fitting but I believe they're suppose to be. I do get a bit a bit off a woosh sound as it comes on boost (not a whistle, I do get that as well) but not sure whether it's excessive or not - could really do with an identical car to compare it against. Could be a bit down on power but that could equally just be me getting use to the car or placebo.

It's going in my local indie garage tomorrow for them to have a look at, as I've not really much in the way of tools, knowledge or skills lol. I think they're gonna swap out the fuel filter, clean the EGR and examine the boost pipes (I'll ask if they can run a leak test on it). I don't believe it's MAF, the symptoms don't seem to add up. Oh and as I said before, battery disconnect to reset ECU learnt values did nowt.

Taking it down to Cambridge over the weekend so I'll report back on Monday with what work was done and whether it's still stabbing me in the wallet every time I drive it...

Edited 12 September, 201213 yr by ckyliu

Sweet let us know, i only getting 41mpg and dont think its right, but ive no symptoms of anything being wrong. Id have hoped for better mpg than this

Most obvious thing to check would be the tyres, make sure they're up to at least 2.4 bar. On a trip of at least 6 miles from cold (in summer), without stop/start traffic you should be getting about 50 mpg over level ground, give or take a bit. I only got 41 recently when the mpg dropped off and even then only have absolutely canning it.

It's got a service with Skoda soon, I'll see if they pick anything up during that. If not I might have to ring up Shark and see how much they'll charge me to check it out and the cost of putting a boost leak right (if indeed, it has one). Then I'll probably remap it lol.

Edited 13 September, 201213 yr by ckyliu

Thermostat not functioning correctly, coolant and fuel temp sensors faulty or going faulty, egr, binding brakes, boost leak are just a few things it could be...

Edited 13 September, 201213 yr by bondi

Sweet let us know, i only getting 41mpg and dont think its right, but ive no symptoms of anything being wrong. Id have hoped for better mpg than this

WOW, that's not good! I average 55mpg when I drive it briskly and well over 70 when being more "conservative"

Last run I did I'm my asz I got 60.9mpg!! All I've done recently was disconnect the egr.

Just be wary of the MPG reported by the trip computer as the BLT engined models display hopelessly optimistic MPG figures, something to do with an error in the conversion from l/100 km in to mpg. Best thing is to work out your MPG based on your miles from a full tank, I was getting about 380-400 before and now it's more like 340-360

Thermostat not functioning correctly, coolant and fuel temp sensors faulty or going faulty, egr, binding brakes, boost leak are just a few things it could be...

Is there a way of testing these sensors?

I told my mechanic about mpg and he was like your getting 40mpg and complaining??? he obviously thinks that great. New mechanic needed maybe, or is an auto spark better for testing those components?

My tyres are pumped and i worked my mpg out by the proper way and my in car meter was only 1 mpg out which is good for car computer.

I never rely on the trip computer - mine is worked out on miles betwen fill ups and fuel at the fill up in litres.

I get regular 420 miles on a full tank in my 55 plate vRS - no idea what engine code that makes it

According to the comp, i'm averaging 50.4mpg - never bothered working it out TBH

I do permanently run a roof rack as well that I never use, so if I was that bothered i'd remove it...

Just be wary of the MPG reported by the trip computer as the BLT engined models display hopelessly optimistic MPG figures

My BLT engined Fab reports about spot on - have measured it several times over several tanks..