Lousy fuel economy mk3 cab 1.6 AFT

[srbGolfmk3]

I will try to find AFR gauge. Before that, check this video, it sounds like some vacuum leak, when I give the gas it sounds like "shhh"... 20170422 153112 1 - YouTube

[Crasher]

If it had an air leak post Air Mass Meter, even a tiny one, this would show as a lambda positive correction error which if over 10% will eventually cause a fault code.

[srbGolfmk3]

Can emission test(gas analizator) show me something about my bad fuel economy?

[Crasher]

Yes as what you need to know is the lambda reading but doing that on the open road is difficult, slow to respond and inaccurate, an in exhaust pre cat lambda AFR gauge is accurate and instant BUT it may show everything is fine and not help you.

[srbGolfmk3]

Damn...still looking for AFR gauge. What about fuel pressure regulator, he can disturb my air to fuel mixture right?What else should I check about this crazy fuel consumption, injectors?

[Crasher]

Whatever you or the fuel pressure regulator does with the fuel pressure, the ECU will always try and maintain a lambda 1 Air to Fuel Ratio. IF the lambda IS working correctly then the car is not using too much fuel, this is why you need to know if the lambda sensor is working properly but I have a feeling it is and the fuel consumption is as it should be, do you drive it very hard?

[srbGolfmk3]

Since the problem with fuel consumption started I drive like a granny... How do you mean lambda 1? I have only one lambda sensor.

[Crasher]

When I say Lambda 1 I don’t mean the sensor itself, Lambda is a measurement, a figure representing a measured value. What Lambda (Greek alphabetic symbol λ) represents is a degree thesis in itself and could fill a book but basically Lambda (and its lower case symbol) is the chosen term for the air to fuel equivalence ratio. In a gasoline internal combustion engine the ideal balance of air to fuel is 14 parts air to 1 part fuel, otherwise stated as λ1=14.7:1 and this ideal balance is known as the Stoichiometric.

When we call the sensor in the exhaust a “Lambda sensor”, we shouldn't, we should call it an “Oxygen sensor”. It’s like when we call a damper a shock absorber, it isn't, it’s a damper and what absorbs the shocks is the spring.

The way your particular version of this sensor works is by sensing the amount of oxygen in the exhaust gases and it is known as a “narrow band sensor” as it only has the ability to work within a small band of the possible ratios, more modern sensors known as “wideband” are able to read very rich and very lean mixtures.

The AFR gauge I suggested uses a Bosch LSU4.9 wideband sensor and this allows you to see if the narrow band sensor is getting out of its operating zone BUT if it was outside its operating range for a long time it would show up as an error.

[srbGolfmk3]

Still cant find AFR gauge. I changed thermostat because old one was faulty, but still not fixed my fuel economy. I will clean injectors, and if that doesn't help, I will change the ECU. Can I put the ECU from 2.0 8v AGG (037906025R) because AGG use same SIMOS system like mine AFT?Is that possible, everything will work fine? Im asking that because it will be easier to find ECU from AGG than for AFT engine...

[Crasher]

There are minor differences to the two ECU's and the AGG will run it richer even if you got it to work and richer is not what you are looking for. No amount of component swapping will reduce your fuel consumption, even if you find and Natalia an AFR gauge and it shows you fueling is correct, what are you going to do? It would mean the fuel conscription you have is correct. I forgot to ask, which Octane (in RON) fuel are you using?