Poor fuel consumption/bad mpg

[Jinxy]

Hello, recently started driving my yellow fab after 6 months of ownership and noticed how bad it is on fuel. Standard car other than and FMIC and EGR delete. Well from what it’s telling me anyway and compared to my last 2 fabs. I’m getting no more the 38mpg where as I’m use to getting 60 average in my last 2. All grandad driving mainly on dual carriages ways and motorways. I’ve recently had my a full belt kit and also had a new temp sensor and thermostat. I’ve also checked for boostleak and everything is how it should be. Is there anything else that could be the causing the bad fuelling other than timing before I investigate. Cheers 

[sepulchrave]

Replace the MAF, I guarantee it's shot.

[J.R.]

A strong possibility but did you miss where he said the cam belt has just been done?

 

Checking the valve timing would be my instinctive reaction.

 

Mind you we dont know how long ago "recently" was or whether the fuel consumption has decreased only in the last 2 weeks or has only been noticed since then, perhaps by having to refuel at less miles than usual.

 

Edited 2 December, 2023 by J.R.

[sepulchrave]

Yes but he's had it six months and it's been thirsty the entire time, the belt change is therefore incidental.

[Jinxy]

My first drive in the car was just over 2 weeks ago now. It’s just been a little project for me. But yeah timing belt has recently just be done. I’m not sure what it was like before this as I never drove it for more than a mile tops if that. I shall swap the mafs over tomorrow from my other fab and give that try. 

[sepulchrave]

I agree that the timing needs to be spot-on but it would run like a dog if it were out by enough to burn that much fuel, it's the MAF, I'm almost certain.

Edited 2 December, 2023 by sepulchrave

[Jinxy]

Swapped the maf over yesterday been on a good 2 hour drive and I’m getting just over 40mpg now. But still poor for a standard fabia in my opinion. Starting to lean towards timing now. I did have a somewhat similar issue on my old one where the cam angle was set back to 0 and the car really didn’t like. Which was resolved with a few hours of messing around on vcds and test drives.I don’t really have nothing to go off with how the car ran before this other than it sounded pretty rough before the timing belt etc was done. 

[cello]

Sticking brake calipers or thermostat maybe ?

[Nasr_1]

I was wondering whether you managed to find the issue or not? As I have a similar problem with my Fabia mk1 1.2 it is averaging around 7 l/100 km on highway and the temperature gage is reading correctly!

[Jinxy]

I messed around with cam timing till I could see no more major improvements, new-fuel filter, maf and it’s pretty reasonable now. Computer says on average 54mpg which is off but tank to tank (40L around 400 miles give or take) i get about 44mpg average.