Terrible fuel consumption

[dancingbear84]

I keep meaning to ask, but not getting around to it. My fuel economy is awful. Like through the floor awful, I used to get around 550-600 miles per tank, driving carefully. Obviously a bit less if I was driving less economically, but always around 500 to a tank.

recently I have been lucky to get 350 miles to tank.

 

i have a friend with vagcom who is happy to test anything I want, but he is only familiar with his vw t4 stuff.

 

would anyone be able to give me some ideas of what to test or change? We looked at the MAF readings and they looked to be reading ok. 

 

My father in law said it could be injectors but I’m sceptical. There is a lot of black residue over the back of the car, I’m guessing is unburnt diesel. 

 

If if anyone can give me thing to try to diagnose the issue I’d be incredibly grateful 

[sepulchrave]

Start with the ECT sensor and the fuel temperature sensor since they age badly, then change the MAF if no improvement.

[KenONeill]

Black suggests over-fueling, which suggests engine temperature is being sensed low, sensed air flow higher than actual, or indeed dribbly injector(s).

[mogwye]

Basic question - When was the last time the Air Filter was changed ?

 

DB.

[dancingbear84]

Air filter was changed at the last service almost a year ago, but this has been going on for a while, I’ll check the ets first I guess

[Guest]

On 02/12/2018 at 19:08, dancingbear84 said:

I keep meaning to ask, but not getting around to it. My fuel economy is awful. Like through the floor awful, I used to get around 550-600 miles per tank, driving carefully. Obviously a bit less if I was driving less economically, but always around 500 to a tank.

recently I have been lucky to get 350 miles to tank.

 

i have a friend with vagcom who is happy to test anything I want, but he is only familiar with his vw t4 stuff.

 

would anyone be able to give me some ideas of what to test or change? We looked at the MAF readings and they looked to be reading ok. 

 

My father in law said it could be injectors but I’m sceptical. There is a lot of black residue over the back of the car, I’m guessing is unburnt diesel. 

 

If if anyone can give me thing to try to diagnose the issue I’d be incredibly grateful - like smkoing 40 cigs a day for 40 years the intake is f******

I would try egr delete pipe and get the fault code mapped out.

[dancingbear84]

I am very slow at getting round to things, it is one of my worse personality traits.

 

Anyway I had a mooch around the engine bay and discovered that the large black hose from the vac pump to the brake assist was "perished" or rather badly split at both ends. I also discovered some perished hose from the n75 to wherever they go.

I have bought some 3mm ID silicone hose and plan to replace this over the next week or two.

 I also downloaded a copy of VCDS lite, I think it is OK to discuss this as it is legit shareware. i just wondered if anyone could advise on what I can check with VCDS lite to point me in the direction of a repair.

I would like to keep the furby on the road for as long as I can, and am happy to fix certain things myself.

 

How can I use VCDS to check the ECT sensor or the MAF, anyone able to suggest anything to point me in the right direction.

[sepulchrave]

1 hour ago, dancingbear84 said:

I am very slow at getting round to things, it is one of my worse personality traits.

 

Glacial even, you've wasted hundreds on excessive fuel consumption instead of fixing a simple issue. Just change the ECT it's a cheap part.

[dancingbear84]

Yeah I’m lazy, the thing was I have literally only being doing about 2 miles a day for the last 6 months. Do you know if it is possible to check the ect using VCDS to confirm it is the issue? I have a week off coming up so am happy to replace the ect or maf or hoses or whatever the issue is if it resolves it, but I’d like to confirm the fault first if possible.

[dancingbear84]

I have taken a reading of the ETS/CTS and the MAF this morning on the way to work, my feeling is the MAF looks more out of whack than the CTS but I don't really understand the logs fully.

This was a sample of a section of the logs taken after around 3 miles when the the dash  was showing the  temp at 90, so engine should have been warm(ish)

 

 

[KenONeill]

OK, will someone who actually knows please state what units the time stamps are in?

[dancingbear84]

Just now, KenONeill said:

OK, will someone who actually knows please state what units the time stamps are in?

 

Looking at the full logs they start at 0.7 and go up in increments of around 1, I would assume that they are seconds since the logging began. In this case I started logging when I started the vehicle, so I would assume around 11 minutes.

[dancingbear84]

Was anyone able to shed any light on this for me? The time stamp is in second increments.

i can run another log of any VCDS blocks that may help. I don’t know what the coolant temperature sensor should read, although 72.9 looked a little low. The MAF looked quite a bit out, but on other runs looked better. 

 

The other her thing I have noticed is that when going up hill under load the tone of the engine changes, it becomes slightly more rumbled/throaty/guttural for a few seconds at around 1800rpm.

 

If anyone is able to help shed light on what I need to test or could let me know the temp of their vrs cts sensor that’d be ace

[KenONeill]

Well, if the time stamp are in seconds, the engine might not be fully up to temperature, regardless of what the lying instrument on the fascia says. If they were later, or the car were a petrol, I'd be suspecting the thermostat was stuck fully open because ~90C is a more typical hot temperature.