My mpg has gradualy tailed off. Now i only get 40 mpg if i drive like a crone. What i have noticed is the car using more fuel ticking over. The computer used to drop about 0.1 mpg ever 60 secs or so. Now its dropping .4 every 20 secs or so. So its not the way i drive or winter fuel, and probely not a boost leak. I have tried a diffent maf, no diffrent. I have a new oem Air filter in place and the fuel filter was changer a few thousand miles ago. Tryes are corrrect pressure and brand new rainsport 2's. So could it be MAP or coolant sensor causing this? maybe a leak exhust side or vacuume or maybe a knacked fuel pump. The timing was done by Skoda when the belt was changer and i have a print out showing the timing is spot on. There is little or no smoke from the exhust. It's bugging me now as its drinking fuel way more than it used too. Any help much appreciated as i just cant keep throwing non existant money at this problem.

Edited 16 November, 201213 yr by RAPTURE

May need to get it scanned for codes buddy.

I have a hand held Vag scanner mate and it shows no codes? Would vcds reveal more? Also my DMF has seen better days, could a dead DMF cause bad mpg?.

Edited 16 November, 201213 yr by RAPTURE

Not really, choked air filter could though.

Worth a try http://www.briskoda....e-up-brilliant/

DB.

Yep tried the Italian tune up , no joy still the same. Im gonna change the coolant temp sensor to rule that out, but again im throwing money at the dark. I hate quirky problems that dont give a error code.

iirc the last time I was idling for long periods of time (it was a cold day!), it certainly didnt drop 0.1mpg per whatever (more like 0.8mpg per 30 secs!), it really depends what was the previous 5-10min drive was. So Im not sure if thats a good/clear indication that something is wrong.

Are you 100% sure that it isn't winter time and diesels doesn't like the winter so much? In my first winter with the vrs I noticed a good 5-10mpg drop, when spring came it slowly crept back up. tyres and size of wheels also make a difference, I gained a good 5-8mpg from 17 back to 16s (when driven sensibly).

knackered fuel pump you will feel hesitation i thought?

leaking exhaust - I wouldn't of thought it will make much difference (since theres a few here with mufflerectomys or less!).

Perhaps oil change? add some fuel additives and give it a blast? try cleaning up the system? rubbish fuel? I know I get less miles and more noise when I fill up at supermarket fuels.

p.s. - thread** (unless you meant tread, then I have no idea what that means)

xD thanks for the replies, i will try run some millers through it, lol yes got tread on the brain after getting my uniroyal rain sport 2's .

Is it measured MPG or using the computer. I wouldn't trust the computer as if a sensor has gone wrong it might not give the correct MPG.

I agree the only way to measure MPG is brim to brim calculation. The fuel computer may be off. There are a few sites which let you track fuel consumption like Fuelly and Spritmonitor.

I'm feeling the pain of poor MPG. See sig.

mine computer mpg went bad when i changed to larger injector nozzles, and then again when i had a remap. but mpg actually improved

Im pretty sure it is the EGR playing up like so many others have experienced. I will have to try a new one.

I recon the computer calculates the mpg based on fuel duration calibration maps. When these are incorrect it puts the computer out. So when fitting different injectors, tuning boxes and some remaps.

Andrew where you upto on finding your problem?

The MPG computer thing on the dash seems to be quite out on mine, it displays about 54 mpg but from using an app on my phone its more like 45mpg. I have noticed about 3-4mpg drop since the winter has come in too.

Hi guys sorry it has taken this long to reply. New temp sensor did nothing, I have tried 2 other diffrent mafs with the same results, struggling to get over 40 mpg on a good run used to be able to get 65 on computer easy so its not just a small drop. Also the mpg display acts diffrently, dropping more just ticking over and not recoveing the mpg when off the throttle rolling like it used to. I know the computer is not the most accurate thing around but the car is drinkng diesel and i am stumped as to why as there is no black smoke from the exhust under any load. I cleared one error on the A/C in vag com and i have no errors now but have not had the chance to take any logs yet as my laptop battery is dead. I will borrow a lappy from my mate to get the logs done so we can see what the engine is up to. Im starting to think Fab is correct and my MAF harness may have a problem. How would I go about getting that fixed if it where the case. Do you have to cut into the loom to replace it?. Im determined to get this MPG problem fixed as i love the car and it goes really well and is reliable. Only other thing i can think of is it seems to pull better on 3/4 throttle than WOT but its not clutch slip, just feel's like it holding back a bit at full throttle. Binding breaks is not something i have investigated yet. I will report back when i have some logs to hopefully shed some light on this. Cheers guys.

Edited 14 December, 201213 yr by RAPTURE

My break was under the battery the garage said.

3/4 is about right. Full throttle won't make any difference. This was done to give a similar effect to throttle response from a tuning box.

Give us a shout if you want it changing.

No i like it . I am very happy with the the way the car delivers the power. Hmm under the battery, i replaced the battery about 7 months ago. Decent battery btw, maybe i disturbed something. I did not think there was any wireing under the battery. Under the battey tray?. I just set my egr to minimum with vagcom and it seems nice and smooth. No wistle like with having it remaped out either, weird but not complaining . John was launch controll enabled? if so what revs is it set too? Does it work the same as this?

many thanks mate i will get them logs done asap.

Edited 15 December, 201213 yr by RAPTURE

I never did see the exact loom location. Just told it was under the battery :(

No launch control setup but it can be easly.

Ok first set of logs, did not manage to get it to the redline so may need to do it again. Was my first ever attempt .

Group A: '003 Group B: '001 Group C: '011 Engine speed MAF (specified) MAF (actual) EGR duty cycle Engine speed Injected quantity Spec. Inj. duration Coolant temp Engine speed Spec. intake press. Actual intake press. D.cycle MAP TIME 790-870 230-310 210-350 40-75% TIME 790-870 3.0-9.0 3-8 °Ck. 80-110°C TIME 2850-3150 2200-2400 2100-2600 35-80% Marker STAMP /min mg/str mg/str % STAMP /min mg/str CF °C STAMP /min % 0 882 265 259.7 69.3 0.42 882 5.2 5.6 83.7 0.82 882 1056 996 21.5 1.22 882 265 264.6 69.7 1.62 882 5.2 5.6 83.7 2.02 882 1056 996 21.5 2.42 882 265 249.9 70.5 2.82 882 5.2 5.6 83.7 3.22 882 1056 996 21.5 3.62 882 265 259.7 71.7 4.02 882 5.2 5.6 83.7 4.42 882 1056 996 21.5 4.82 882 265 259.7 71.3 5.22 882 5.2 5.6 83.7 5.62 882 1056 984 21.5 123.93 1911 645 671.3 51 124.33 2016 48 15.3 83.7 123.52 1827 1500 1488 47.4 125.13 2478 850 1185.8 4.8 125.53 2688 65.9 26 83.7 124.73 2205 2472 2292 66.1 126.33 3024 850 1127 4.8 126.73 3213 63.4 27 83.7 125.93 2835 2508 2520 64.5 127.53 3192 850 548.8 4.8 127.93 2436 0 -0.5 83.7 127.13 3213 1104 1896 63.4 128.73 2310 275 553.7 4.8 129.15 2247 0 -0.5 83.7 128.31 2331 1008 1308 36.7 129.93 2142 255 529.2 4.8 130.33 2079 0 -0.5 83.7 129.53 2205 1008 1236 35.5 131.13 2016 245 519.4 4.8 131.53 1995 0 -0.5 83.7 130.73 2037 996 1212 32.7 132.31 1911 245 514.5 4.8 132.71 1869 0 -0.5 83.7 131.93 1974 996 1200 31.5 133.51 1722 245 470.4 4.8 133.91 1701 0 -0.5 83.7 133.11 1806 996 1188 29.9 152.73 2352 850 1122.1 4.8 151.91 1974 33.8 11.2 83.7 152.31 2079 2364 1716 33.9 153.96 2940 850 1136.8 4.8 153.14 2604 65.9 25.5 84.6 153.54 2772 2508 2508 63.8 155.17 3486 850 1053.5 4.8 154.37 3129 64.8 27 84.6 154.77 3318 2520 2484 64.9 156.39 3717 850 744.8 4.8 155.57 3633 60.7 27 84.6 155.97 3780 2520 2460 64.1 157.59 2730 710 588 4.8 156.79 2982 0 -1 84.6 157.19 2772 1020 1488 38.6 183.01 882 265 254.8 70.9 183.41 882 5.5 6.1 85.5 182.61 882 1056 996 21.5 184.21 882 265 269.5 69.3 184.61 882 5.2 5.6 85.5 183.81 882 1056 996 21.5

Only manged to get it to 3700 rmp and already i can see the maf readings look fudged. :(. Neadle was bang on 90c for 10 mins but would not get hotter than 85c acording to the log. It certainly did not fell like it wanted to rev to the redline in 3rd :(. Any help with this much apprecated.

Edited 16 December, 201213 yr by RAPTURE

I have just had a pair of rainsport 2`s fitted and have had a noticable 4/5 ish drop in MPG :(

Hmm my rainsport 2's have only been on about 600 miles, wonder if this is contributing.

This might be useful in detrmining a faulty MAF

http://www.niovus.com/personal/mass.pdf

I think you need to log more data up to wide open throttle (WOT). Your current data is shown on the attached graph, which I sampled from the best block of data where you managed to get to 3192 rpm.

In general the actual MAF exceeds the requested MAF, which I think means your MAF sensor is ok.

I think you need to see how many miles you get out of a tank!

*

Edited 18 December, 201213 yr by Chorlton