critical fuel consumtion..1.9tdi

[paddyd99]

Hi all,

Im a cabbie here in Ireland with a major problem. My new (for me) 2003 skoda octavia automatic is absoloutly guzziling diesel.Ive always been a Toyota man due to their reliability. My last car was a 1.6 petrol avensis that was heavy on juice but reliable as a clock. I decided to change to a diesel skoda due to their legendry fuel consumption and the automatic gearbox is great in traffic. The car looks perfect,drives perfect, 74,000 on the clock,1 owner but hell does she drink juice.I know Im a heavy driver, most of my driving is done in the city at night and I dont hang around but on the first few fills ive barely being scraping 29 mpg out of her...Its been as low as 26..When I bought her, the guy said he did the timing belt and replaced the radiator due to a light crash....My own mechanic said that it was a small crash and that the repairs were top class...any ideas anyone..........help..oh also I forgot to mention, sometimes but rarely...once a week or so...when im stopped for a bit and go to start her the engine wont fire...she turns but wont fire....then all of a sudden she will start and run perfectly on the 4th or 5th attempt.

[ini]

If it is the older TDI engine (not PD) i would check the fuel pump timing?

[paddyd99]

thanks for the reply ini,
Im nearly sure its the old tdi engine allright. Can I check the fuel pump timing myself or does it have to go to the dealer. Would any mechanic know what I was talking about if i left it to them??

[ini]

The injection pump timing needs to be checked using an OBD cable & vagcom or garage/dealer equipment.

[greg123]

Agreed. Being as the auto is a heavy failure point (and part of your problem is the auto box isn't locking up until 3rd or top by design, so it's using a lot more fuel than a manual) you can get some improvement by flushing the box, changing the filter, upping the line pressure (called the Kerma line mod, look on tdiclub.com) and I prefer to use an additive and Valvoline fully synthetic fluid which they specify as being equal or better than the VW fluid - which is not fully synth and to my mind not as good. This has made a BIG improvement in the feel of the box and I try to push it to customers as it may also save the box, which often go around 80-100k if not had something like this done due to the fluid not lasting out (even though it's supposed to be 'sealed for life' which is just absolute ba**s). I also prefer to hard code the box to sports mode not adaptive as often it's changing up too early on light throttle from stock and the slower the TC spins the less efficient, plus it means you are always changing up and down gear which is annoying, the sport mode holds the gears a little higher and keeps the rpm at a more eficcient level.

As for the car, as above check the pump timing, you'll also see a bit of improvement by having the dynamic timing advanced 3 or so degrees, that's done electronically and I get better performance and economy. The EGR is awful on these, get the inlet manifold off and have the ports and manifold cleaned then clean all the intake piping and using a blanking metal gasket to blank off the EGR. Have the car scanned for fault codes and make sure it's well serviced. Run a bottle of professional injection cleaner through the tank.

Pump the tyres up to around 35f 38r psi providing you are still getting good grip in the wet and that it is below the max pressure printed on the tyre - mpg likes higher tyre pressures.

Check you have the engine undertray and the under bumper and side engine covers all present - this can help mpg on a run.

Then let us know how it goes and any fault codes found after the fault code scan. The car should perform well at 70mph when cruising so do a run in it without going crazy and see if you are getting up near the 60's mpg mark on a run. If so, your engine is probably running right. Overall I'd expect 45mpg from your motor if doing a fair bit of town work. Try not driving it so hard for a tank full and see how you go.

The octavia tdi is one of the best cars for mpg in the world, but the auto it's amazing and does blunt it. We get 65mpg on a run from my friends two tdi's I look after and 55mpg overall with town. I know a taxi driver that did mainly longer runs and averaged 63mpg over the life of the car! And another that got 71mpg, somehow. You won't find another make that beats that. Not in this size of car!

Greg.

[maciek_m]

you'll also see a bit of improvement by having the dynamic timing advanced 3 or so degrees, that's done electronically and I get better performance and economy.

could you elaborate on that please? I'm having similar issues with vw bora tdi with 5spd automatic... 33mpg average seems a little low to me...

[greg123]

I'm afraid you have the PD engine, you cannot alter static or dynamic timing in the PD. In the pre-pd VP37 pump tdi, you can set the static timing to 70@110 on the computer and as I said do a dynamic advance, they run nicely then. However with the PD go to a good chip tuner who optimises engine, not just adds fuel, and they will alter the timing, boost and fuel maps and you should get a dose more performance as well as up to 10mpg more economy. Narrower (but not smaller diameter) tyres run at a higher pressure such as conti eco-contact or similar & disabling the egr system can also help.

Greg.

could you elaborate on that please? I'm having similar issues with vw bora tdi with 5spd automatic... 33mpg average seems a little low to me...