MK7 starting issues

[HonkeyGonk]

Hi all,

I have a 2015, MM7 GTi PP (manual) which has developed an issue during start-up.

So Ignition on, lights all fine, no errors, press the clutch in and turn the key after 30 seconds or so.

The car cranks and starts but stutters instantly, never fully starting. Acceleration peddle doesn't do anything to keep the car alive. I then get an error on the dial area that says the ACC has been deactivated but thats it.

In some cases, the car tries to start again (like the start stop) but same outcome as above.

I took it to a local garage, who knew that this was most like a water sensor issue in that it it thinks the car is colder than it is, so the fuel/air mixture is too rich to start. We had both water sensors replaced in March 2022, but when the outside temp went to 6.5 degrees, the issue re-appeared.

Has anyone had a similar issue? Any solutions?

Thanks in advance and sorry for any missing information!

[Exonian]

Welcome HonkeyGonk

Have you had the battery checked for voltage?
Does the car get left out in the open not being used for periods of time?

[willni]

Welcome,

Following on from Exonian, when were the spark plugs last changed? Also what fuel are you running? not unheard of to get bad fuel.

[madstaff]

First thing to do is to get it hooked up to VCDS or a similar fault code reader and scan for fault codes.

There's obviously a fault somewhere as ACC no longer works.

Could be 101 different things as there's that many sensors on a modern petrol.

No one will be able to say its "that sensor" until you've scanned for codes.

[HonkeyGonk]

Hi everyone,

Thanks for the quick responses everyone!

@Exonian - We haven't, would the engine still crank and stutter if voltage was low? We had a 2+ hour trip the day before and it gets used daily for motorway usage so hoping it wasn't battery?

@willni - Plugs were changed during last major serive, May 2021 at 46k miles (now at roughly 66k) Running Texaco Premium Petrol (95 Octane)

@madstaff - Last time this happened there were no error codes at all. Once the car starts up, the ACC works fine. The chap at the garage happened to have experience and said about the water sensors. On his display, it was reading as -31 degrees so was faulty at the time but I can't believe new sensors have done the same thing within 8 months?

[Lordie]

It's been a very long time since it was last scanned for fault codes. Step 1 would definitely be to scan it again. The battery would be the other obvious thing to check. Even if you did a long drive before, it could still be nearing the end of it's life or not recharging properly

[HonkeyGonk]

Hi Lordie,

A fair point, sadly it's not booked in until next Friday so codes will have to wait!

We can't see any battery changes from previous owners and we haven't. So it could be on its original battery from 2015! Is there a way to know? What brand would it have come with?