Misfire on idle an issue?

[clarkj93]

So does anyone know if an engine misfiring on idle only due to an injector causes any long term engine damage or other issues? Wondering how much time I have to get it sorted as the budget on my build is already wildly out of control I could do with leaving it for next year!

Just to note it runs perfectly when under load or above idle rpm, it's only in cylinder 1 on idle every 5 seconds or so.

Car is a 2008 golf gti.

[paintman]

Cat damage from unburnt fuel?

[toohuge]

Misfires at idle usually suggest some form of
vacuum leak iirc.

Are you sure it’s an injector ?

[clarkj93]

I think it's running lean on that cylinder if anything. Yes definitely the injector all vacuum lines or hoses either changed or thoroughly inspected but real question is if there is any long term damage here or if I can leave this to worry about it another time.

[toohuge]

Ideally you’d sort / diagnose this properly at this stage before leaving it. I’d be tempted to do a compression test at the very least to eliminate a leaky cylinder (which can cause a misfire at idle).

As for damage, potential cat damage and, theoretically, there may be the chance of cylinder washout diluting the oil leading to huge issues.

[clarkj93]

toohuge said:

Ideally you’d sort / diagnose this properly at this stage before leaving it. I’d be tempted to do a compression test at the very least to eliminate a leaky cylinder (which can cause a misfire at idle).

As for damage, potential cat damage and, theoretically, there may be the chance of cylinder washout diluting the oil leading to huge issues.

I thought as much. I wish you lied to me and said it would be fine

[Zener]

Some ECU's shut down the fuel inj on the offending cyl if constant misfire counts get detected by the ECU this only resets on key off and engine run until the ECU detects the same misfire again , cant see it being a faulty inj just malfunctioning on idle only thats not a fuel injector fault I've ever witnessed

[clarkj93]

Zener said:

Some ECU's shut down the fuel inj on the offending cyl if constant misfire counts get detected by the ECU this only resets on key off and engine run until the ECU detects the same misfire again , cant see it being a faulty inj just malfunctioning on idle only thats not a fuel injector fault I've ever witnessed

It's rare enough that it never triggers an EML light or code and subtle enough only I really notice it as I've owned the car long enough I know it inside and out, otherwise anyone else would only detect it with something in the obd port counting the misfires which is how I know its about every 5 seconds.

I agree with your scepticism but just seems like most likely option as I used the liqui moly fuel cleaner just before it started misfiring and I have heard of this causing misfires in injectors before and have known a few other golf gti owners with an idle only issue before, something about low cycle issues with them? I'm a home d.i.y'er mind so can only speculate but a VAG specialist tuner also seemed to think it was an injector playing up from the symptoms.

[Chrismawa]

I had this on my old 2.0 TFSI A4. Inlet valves were all cogged, needed a decoking.

[zakmuh]

I wonder if misfring would put strain on crankshaft?

I had misfiring but car didn't throw any error code on the dashboard. Only the scanner told me about it