Fuel consumption problem

[Adrian81]

Hello everybody!

Since last year i am the owner of a 2008 Skoda Octavia Tour. I bought it from a guy who made from 2008 till 2013 137.000 km. It seamed like a lot but when a friend went to see it and buy it (i wasn't in town at that moment), seamed like the car was driving OK. When i got home and started to drive it i noticed that the display was reading a great fuel consumption value. The car has an TDi, AXR engine of 100 hp and the fuel consumption is around 8.2 liters per 100 km outside of the city, going around 100 km/h. In the city, the display reades from 11 l to 16 when it is traffic jam. I went to 2 of the Skoda authorised workshops in Bucharest and i argued with them because from my point of view was a waste of time. First time when i went to them, the car was in LIMP mode, but i also told them about the fuel consumption. Their answer was to change the turbo vacum capsule because it was broken. I replaced it and the LIMP was gone bu the fuel consumption was the same. After that i went to another service and talked to someone to change the ECU software because i thout that the guy who had the car before me changed it and changed it badly. The guy changed it and said that the problem is not the software because with the original stock software, the car fuel consumption is the same. I went back to the Skoda authorised workshop and argued with them because he last time thy only solved one of my problems. After 3 hours of waiting, they came and said that the car software was to blame and they advised me to go and put the original because with their tools, they cannot do that. I left there with the ideea that the guy who had put the stock software in my ECU didn't know what he was doing so i went to another software remapping company. The result after re/reinstalling the stock software are the same. The car drives very good, and from what i knowticed, there's no extra smoke, and accelerates better that a Skoda Octavia 2 with a 105 hp engine.

Since now i veryfied the following: MAF sensor, EGR, G81 fuel temperature sensor and all were ok. The next step which was recomended by a friend is to check the fuel injectors. On VCDS it displays that the quantity delivered by the injectors is OK. On iddle, i have a normal consumption of 0.6 l/h so the problem is only when i accelerate it.

On VCDS the only value that is out of range is the MAF value but i was told that this is because the EGR is turned off from the software so there's no reason to be concerned. 

So, what would you advise to do next?  

[rwbaldwin]

The first thing you need to do is to calculate the fuel usage between fillups. Don't rely on the displayed readings.

[Adrian81]

I allready did that. The fuel usage is as big as it's being shown. I mean, whith 32 l of diesel i'm doing 400 km on the highway, going at about 100-110 km/h. That means 8l/100 km which for that speed is clearly not right.

[rwbaldwin]

Did you check the coolant temp sensor?

It is a 2-channel temp sensor on the AXR. One goes to the dash temperature gauge (G2) and the other goes to the ECU (G62). If G62 is faulty, the ECU may think the engine is always cold and use more fuel.

I'm assuming you have already checked for fuel leaks.

[Adrian81]

I thought that was the G61 sensor...Anyway, i didn't check the sensor physically but i took a look at the values of the fuel shown in vagcom and are preatty normal.  From what i remember, there was a difference of 10 celcius degrees between the fuel temperature and the coolant temperature. Is this normal? I Googled this problem and read that if the value is negative, the sensor is bad. Mine is positive.

Oh yeah, no fuel leaks

Edited 7 October, 2014 by Adrian81

[rwbaldwin]

Check G62 against G2. Are they the same?

A failed sensor doesn't always go negative.

[Adrian81]

Ok. I hope it doesn't sound silly but how do i do that? I googled and found out where the G62 is located. Since is not so expesive, should i try to replace the G62 anyway?

PS: the car seams to warm up very slow compared to a friend's Skoda Octavia mk2. Can this sensor be the reason for my troubles?