I would just like to ask, I have been having issues with the car for some months, very intermittent, fuel economy will drop sometimes, in the past I got the engine light on and a P2177 but not that often. I was wondering if I could have an injector sticking open a bit. So I looked at injector testing on the internet and most were send away for testing costs around £18 to £25 per injector.

Doing another search I find one can buy the injectors new for a similar price each. But my question is this, is it just a matter of swapping them or do I need to change settings within the Engine management via ODB2. I ask because when I had a diesel Mondeo each injector had a code that needed to be entered when swapped, I know this is a petrol and may be simpler but I need to ask?

Cheers

Adrian

First thing I would do is fill the car with a good tank of premium petrol and a can / bottle of injector cleaner.

I use Tesco Momentum petrol and something like Redex petrol injector cleaner.

Then when this is in the car and the engine is hot, use the engine firmly.

I go up a long hill using full throttle in a lower gear with the revs above 4k all the way.

Obviously clear the code first and then see if it or another code comes back after the above.

Thanks. AG Falco

It is good that you have also suggested that to try as I have started that already. It was a suggestion to me by the auto garage trying to diagnose the fault. It is on 3/4 of it's second tank of Shell petrol and it's second bottle of injector cleaner. The bottles are supposed to be for 60 litres but the tank is only 35 litres so should be close to a double dose of cleaner!

I notice one can get the injectors from just under £13 (UKP) up to over £100 each depending on make. From Borsehung B11165 at the cheap end to the Meat & Doria 75114832 at the other end with Bosh at around £80.

But I do not know if it is just a matter of fitting new ones or if settings have to be changed?

Adrian

Just to add a comment, the fault code is not showing at present although fuel consumption has dropped around 15%. When the engine is warm after being on a run, I am monitoring the voltages of O2 sensor 1 and O2 sensor 2 at tick over, I was told to expect the first to cycle between say 1 Volt and 0 volts as the system maintains the correct fuel mixture to the engine, this is not always happening the O2 number 1 sensor stays high and the O2 sensor no 2 is around 0.8 Volts.

But sometimes all is OK and No 1 cycles and No 2 drops to probably around 0.4 - 0.5 Volts. The ECU has been checked OK. Checks have been made on the vacuum system for any leaks the exhaust CAT was replaced a few months ago because of this fault. But it is that intermittent, leaving it with a garage has meant I have been without a car for several weeks waiting for the fault to occur and stay log enough for them to find it. So looking myself at replacing/doing what I can.

As there are no ports to check pressure on the fuel line I can not check the fuel pressure, but assume if the pressure was low, I would loose power at motorway speeds which does not happen?

So always open to ideas for things I could check/try. I have the Torque ODB2 app on my phone but that is about it.

Adrian

5 hours ago, AdrianPH said:

fuel economy will drop sometimes

I keep full tank to full tank, MPG records going back 20 Years.

They will vary over the year by over 20%

1 hour ago, AdrianPH said:

exhaust CAT was replaced a few months ago

Genuine or aftermarket?

5 hours ago, AdrianPH said:

P2177

Any codes now?

Thanks. AG Falco

No codes at present.

Aftermarket Cat, I could not justify a OEM one at over £1200 for a 10 year old car. The cat was supposedly damaged due to over fuelling?

When clear of the problem the car will happily average 60+ mpg on my motorway journeys this is with the aftermarket cat.

When the fault is starting it drops to around 45 for the journey (same journey). Previously, during a particular bad run before the fault code light came on, I watched it drop from high 50's to 25 mpg on a straight motorway run. This is the instantainious mpg reading on the small Garmin screen.

So back to my initial question, can I just put in new injectors to see if it clears the fault, or are there changes that need to be done via an ODB tool on fitting them? £60 as a try could be better then the £800 plus I have spent already without clearing the fault.

Adrian

20 hours ago, AdrianPH said:

No codes at present.

I would wait until / if the fault appears and then do a full scan.

Some systems will give you more detail than just a generic P2177 code.

Some can give you live data as well.

This also might help in your diagnosis.

I use OBDII.

20 hours ago, AdrianPH said:

When the fault is starting

Does the engine have a drop in performance at this time?

Thanks. AG Falco

3 hours ago, AGFalco said:

I would wait until / if the fault appears and then do a full scan.

Some systems will give you more detail than just a generic P2177 code.

Some can give you live data as well.

This also might help in your diagnosis.

I use OBDII.

Does the engine have a drop in performance at this time?

Thanks. AG Falco

I am not aware of there being any other codes, even the auto electrician I have had it back to only quoted that number to me, see this previous post on the past history. https://www.briskoda.net/forums/topic/532791-possible-ecu-problems

The car is unfortunately still giving poor mpg when it feels like it, very intermittently, many a time it can be fine then on a run it drops, then next time OK.

As to engine performance, I do not notice poor performance, then again I am not trying to push the car hard, when it did drop to the low figures I would occasionally get what felt like a miss fire, a sort of stutter. But nothing like that recently.

The app I use Torque with the adaptor is ODB2, and I do monitor live the O2 sensor 1 and sensor 2 as mentioned earlier when I think the fault is occurring.

21 hours ago, AdrianPH said:

I would occasionally get what felt like a miss fire, a sort of stutter

Can you check for misfires?

Spark plugs, Coil packs?

21 hours ago, AdrianPH said:

see this previous post on the past history

I just re read that post. I commented on that post as well.

Are there any common times when the fault occurs?

Long journey?

Cold weather?

Damp / wet weather?

Thanks. AG Falco

The original fault started around April/May when it went in for the CAT, and now we are in Winter I could see no dependence on hot, cold, wet, dry. The car only gets used on journeys over 30 miles. I have to trust that the auto electrician went through testing of things like the 3 coil packs. I certainly do not feel any stuttering for the majority of the driving, even when I can see the mpg drop. I would think that as only having 3 cylinders if one started to miss it would be noticeable. As I said only when the screen started to indicate very low mpg did I notice anything.

Last service was in July and it was running fine at the time.

I think I need to contact my friend again with the VAG software to ask about any ODB2 work when changing injectors, if it does not need it or he can do it for me I will just swap them.

Still awaiting my mechanic friend to get back to me.

I used the app again yesterday as the fault once again reared it's head with the PID mpg dropping to 36 on a flat motorway journey down the M55 at 63mph. And yes I do think it looses power as the throttle response was not as expected when the problem was showing. When back at home I used the mobile app and it showed a "Pending Fault P2177 Power Train System too lean off idle bank 1". No other indications.

Now just thinking out loud and wondering how the PID calculates the MPG reading, and wondering if it is using the injector pulse width together with the road speed from the ECU to work out a figure. The wider the pulse width or 'ON-Time' the more fuel it uses, in which case I wonder if this could be pointing towards low fuel line pressure. I have nothing to test this with and I notice there is no Schrader valve on the fuel line, so the lines would have to be disconnected and a gauge placed in line. So looking what is available to remove the fuel line connectors and test.

This might help : -

Thanks. AG Falco

Managed to do some testing today. Bought a fuel pressure gauge over the weekend pressure at 3.4 bar around 49 psi so that looks OK. Took the fuel rail off with injectors,checked the injectors were not leaking, also placed plastic tops over the outlet of each one and turned over the engine for around 18-20 seconds and then weighed the tops with petrol in them and all around the same at 9 grams plus or minus 0.02gram, so I think close enough. No signs of leakage around the exhaust to engine manifold, no gas burns around the O2 sensor so not suspecting a problem with air in the exhaust.

What I have also done is taken off the Evap to inlet manifold for the time being and blocked the manifold hole. The engine is running fine at the moment with no signs oof the issue so will test for some time the reconnect and see if the issue comes back, not sure if there is a vacuum gauge that can be fitted to monitor that system or not.

How the hell does one disconnect the plastic fuel line connectors where the line come up near the engine on the side of the suspension turret? Tried pushing in the clips pulling twisting etc.

An update. After doing several small trips and a couple of 70 mile journeys. I soon found that after blanking off the Evap inlet, the mpg readings were once again excellent, back to the 60+ region for my typical runs. I got an EVAP error PO441 quite quickly when travelling on the motorway, but no running issues, and after a few days of similar mpg readings I bought a replacement EVAP valve from Ebay, in fact I bought two both at under £9 each Although I could not find one listed specifically for my can I just went for the same part number from the old one, 6QE906517, seems to be a popular one for Audi, SEAT, Skoda and VW.

So at the moment all seems well and I am starting to get back confidence in my car. Just annoying that I was told it was tested and was fine. Time will tell but at the moment keeping fingers crossed it stays fine.

Adrian

On 17/11/2025 at 22:00, AdrianPH said:

No codes at present.

The cat was supposedly damaged due to over fuelling?

Code P2177 and cat damaged due to over fuelling says coil pack issue to me. The over fuelling happens when the offending cylinder is misfiring . Can be weather sensitive.

Edited 1 January1 Jan by bigjohn