Skoda Octavaia ASZ 130 low power and fuel efficiency

[rephlex]

Hi I'm trying to find out whats wrong with my skoda and I thought you guys might be able to help.. I've got no power below 1.7k revs and the fuel efficiency isn't great. It takes around 3 seconds in first gear to go from 1k to 1.5k revs in 1st and the fuel efficiency on the dash reads 39mpg doing 70mph on the flat. Actual MPG is a bit better, I got 44mpg on a 300 mile motorway trip. There are no fault codes.

 

I've had it tested and the mechanic can't find whats wrong apart from he said that the turbo is a bit slow. I've already replaced the MAF sensor and this made a huge difference to the power at low revs but there is still a fault somewhere..

 

I've cleaned the turbo with the mr muscle treatment, done a good italian tune, put a bottle of injector cleaner through it, done a full service (all filters + oil), cam belt, aux belt and water pump but none of these made any difference.

 

There was also some oil residue on the surface of the coolant but the garage was almost certain that it was the oil cooler so I've replaced that and hopefully that will clear it up.

 

Can anyone help?

Cheers!

[yesiamtom]

Is the car definitely getting up to temperature? 

 

Seems to be a lot of people in recent months on here with faulty thermostats and what not. The engine never gets up to temperature and so suffers awful fuel economy. 

[rephlex]

I've checked both the coolant and the engine temperature and the both are held at 90C once the engine has warmed up.

[Titanium_Man]

How are your lower boost connections? Mine are very loose and suffer terribly around town but does get a littler better on a run, but still off what it should be by a fair way.

[rephlex]

Which ones are the lower boost connections? The boost pressure was tested and was OK. Do you know how the computer calculates fuel consumption? I had assumed that it measured the fuel at the injectors but it's so inaccurate that it must be doing something else.. Maybe something like just using the throttle position sensor and speed. If the injectors were slightly blocked would the ECU measure actual fuel rate and compensate for it or does it use some sort of feed forward control? It feels like the car is running lean..

 

What sort of MPG should I expect on a motorway trip with this engine? (70-80mph, 3 people)

Edited 5 January, 2014 by rephlex

[Titanium_Man]

Which ones are the lower boost connections? The boost pressure was tested and was OK. Do you know how the computer calculates fuel consumption? I had assumed that it measured the fuel at the injectors but it's so inaccurate that it must be doing something else.. Maybe something like just using the throttle position sensor and speed. If the injectors were slightly blocked would the ECU measure actual fuel rate and compensate for it or does it use some sort of feed forward control? It feels like the car is running lean..

 

What sort of MPG should I expect on a motorway trip with this engine? (70-80mph, 3 people)

 

My pipes to my SMIC are really loose and loosing pressure, although no official pressure test has been done, but it is obvious when you look and had a pull and push I am no car engineer, but my assumption would be that it would need more work from my engine to get up to speed and therefore use more fuel? 

 

I'm not sure on the stats for your car TBH. How out is your computer? 

[rephlex]

I've not had a look at the intercooler yet but the car feels under fueled and never smokes even under heavy acceleration so I don't think its losing air. When the weathers a bit better I'll take it off and give it a clean.

 

The computer is out by around 5MPG on average and the actual fuel consumption isn't actually that bad, it's just the power that's lacking.

[Titanium_Man]

TBH, 5mpg out is what I would expect. Have you done any VCDS logging? Possibly worth getting someone local to hook it up? Checked your rear callipers to check they are free?

[yesiamtom]

My computer over estimates by 4-5 mpg.

[devonutopia]

3 seconds to go from tickover to 1500 revs in 1st?  That sounds very odd!

[mbames]

vacuum leak / faulty n75?

[rephlex]

I've got torque so I'll take it for a drive to get some graphs of vacuum / rpm / boost.

 

It even takes a second to go from 1k to 1.5k when in neutral. As long as I don't drive below 1.5k rpm when accelerating the car feels OK. At 1.7k you get a real kick in the back from the turbo kicking in.

 

Computer is under by 5mpg.

[mbames]

If the trip mpg calculations are anything they are on the generous side.

 

In neutral things are a bit different, so don't read too much into that.

 

Try logging expected vs actual (block/channel 11 on vagcom/vcds).