MPG has suddenly gone from kind-of-okay to worst

Sylvester said:
MOT was done 3 months ago, passed emissions first time, of that's a good indication. Cheers

I've done that before and the temps shown were rather accurate, like when it showed ~85C in car, it'd shown ~83C on the connected device, but I'll try to check it again.

Meanwhile the slightly wandering temp isn't great, the issue always been the same, if the open thermostat had got worse in last few weeks, tempwould've ve gone lower more, but it does the opposite lately and stays on 90rud much steadier. Thanks
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Logging over a decent run, (time), is the only way really. Instantaneous comparison with the gauge is no guide. If you choose your log groups carefully, you'll get a real insight.
Mac.
 
RAB said:
The "temperature gauge" is more of a comfort gauge than anything else. Just compare the gauge reading with the actual temperature shown by VCDS.

RAB
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Yes I've done that before, I've mentioned it above, but I might have a look again, cheers.
 
I reckon change the plugs and thermostat before doing anything else.

Does anyone know if a genuine thermostat is advisable on the 1.4 petrol, as it is on the diesels?
 
The last addition to our AUA after replacing most of the ignition / fuelling components over the previous 3 years was a new pre-catalyst lambda probe (NTK/NGK). Improved the fuel efficiency around 15% overnight (with me driving) - I was surprised how much of a difference it made.
 
I bought an FSI, lousy consumption and emissions. The owner reckoned it needed a new cat among other things but a scan at WOM showed the ECU thought it was running at -20C so it was running super rich. One new temp sensor later it was fine.
Has it been scanned by someone who really knows A2s?

George
 
George Hogg said:
I bought an FSI, lousy consumption and emissions. The owner reckoned it needed a new cat among other things but a scan at WOM showed the ECU thought it was running at -20C so it was running super rich. One new temp sensor later it was fine.
Has it been scanned by someone who really knows A2s?

George
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I've changed the temp sensor few months ago, had cost a nice £60.
I scan the system every few months, apart from me no one though. The only issue shows up is the intermittent yaw sensor, but I know about that.
I wonder what setting is that to see what the ecu/cccu does? Cheers
 
Robin_Cox said:
The last addition to our AUA after replacing most of the ignition / fuelling components over the previous 3 years was a new pre-catalyst lambda probe (NTK/NGK). Improved the fuel efficiency around 15% overnight (with me driving) - I was surprised how much of a difference it made.
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That is interesting, I was actually looking at that few days ago while trying to sort the cv boot.
Is it the one sits on top, just front of the cat? Cheers
 
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Sylvester said:
I've changed the temp sensor few months ago, had cost a nice £60.
I scan the system every few months, apart from me no one though. The only issue shows up is the intermittent yaw sensor, but I know about that.
I wonder what setting is that to see what the ecu/cccu does? Cheers
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Did you change the sensor yourself? I’m asking as an OEM one is around £50. On your scan can you see the temp that the sensor is reporting to the ECU, that’s the important thing. The one on that FSI reported “normal” temps at the gauge but -20C to the ECU. I’m not sure if it shows as a “fault”.
 
George Hogg said:
Did you change the sensor yourself? I’m asking as an OEM one is around £50. On your scan can you see the temp that the sensor is reporting to the ECU, that’s the important thing. The one on that FSI reported “normal” temps at the gauge but -20C to the ECU. I’m not sure if it shows as a “fault”.
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Yes I did change itself. I see, I'd actually checked that during driving before, back then it was almost the same value, probably it worth to check it again though, just to be sure. Thanks
 
Sylvester said:
That is interesting, I was actually looking at that few days ago while trying to sort the cv boot.
Is is the one sits on top, just front of the cat? Cheers
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Take the heat shield off the exhaust manifold, it screws into a threaded port there, yes. A non-OEM generic one was fitted by the garage when the MOT required it 4 years ago, but before Christmas we had repeated "short to ground" fault codes with the lambda, so I hunted down the appropriate NTK / NGK one for a decent price and got that fitted (no connector splicing needed unlike the previous one). Fuel economy improvement tank to tank was obvious even though it was winter time.
 
audifan said:
You have checked that it is not a fuel leak from pipework, the tank or filler cap?
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Yes I've checked it and there's no fuel leak prior or after the fuel filter change. Cheers
Robin_Cox said:
Take the heat shield off the exhaust manifold, it screws into a threaded port there
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Is it a simple twist-in sensor or needs tinkering/cutting? The ones I saw online (Autodoc) come with a cable attached. Might be the post-cat sensor?
preview.jpg


I think the heat shield is missing under the catalytic converter, it's probably worth getting a new one anyway. I'll put the car on the ramp on Sunday after work and take a few pictures just to be sure. Cheers
 
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Sylvester said:
Yes I've checked it and there's no fuel leak prior or after the fuel filter change. Cheers

Is it a simple twist-in sensor or needs tinkering/cutting? The ones I saw online (Autodoc) come with a cable attached. Might be the post-cat sensor?
View attachment 109352

I think the heat shield is missing under the catalytic converter, it's probably worth getting a new one anyway. I'll put the car on the ramp on Sunday after work and take a few pictures just to be sure. Cheers
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The proper NTK/NGK part has a cable and the correct plug attached. The ones with bald cables are generics that you need to swap the old connector onto. From memory the front lambda is the "5 wire" one as well. No tinkering or cutting needed. Access to this is from above with the bonnet off as far as I am aware.
 
Robin_Cox said:
The proper NTK/NGK part has a cable and the correct plug attached. The ones with bald cables are generics that you need to swap the old connector onto. From memory the front lambda is the "5 wire" one as well. No tinkering or cutting needed. Access to this is from above with the bonnet off as far as I am aware.
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I've had a look, on how to change pre-cat O2 Nox sensor and the wire supposed to go through the floor to the ecu, next to the cccu, under the passenger seat compartment?
This is from Aj's older post, if I'm correct, the sensor supposed to be item No. 20, Bank 1. He explained both marked No.20, but they're very difference, hence the bank 1-2 signs.
Screenshot_20230617_160602_Chrome.jpg

Cheers
EDIT: THIS IS 1.6 FSI LAYOUT, NOT 1.4 PETROL.
 
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