Need a little help, idle problem

[Callum Hill]

Hello, I have tried searching on here but not really had much luck, I have a 2001 a3 8l 1.8t drives spot on until it sits on idle and the needle hesitates. doesn't move a massive amount but wont sit still and its annoying me, I have so far done a major service including plugs and fuel filter but still does it also no codes in the system any ideas?

 

[<tuffty/>]

1.8t's don't have a brilliant idle tbh... they do jump about a little, never seen one with a rock steady needle... if its stalling out though its most likely a vacuum leak... smoke test should reveal it..

Split hoses etc are a very common problem on any VAG car with a 1.8t in it

<tuffty/>

 

[Callum Hill]

Oh really? um wouldn't I have lack of power if I had a leak it seems to be fine, ill have a check of it when im fitting the Cambelt don't have a smoke test machine at work so will have to do it the good old fashion way with a torch haha! surely if it was anything major ide have a code stored, its not massively bad just would have thought it should be steady not erratic like it is ? thanks for your help again

 

[Callum Hill]

*forgot to put its never stalled before*

 

[<tuffty/>]

Oh really? um wouldn't I have lack of power if I had a leak it seems to be fine, ill have a check of it when im fitting the Cambelt don't have a smoke test machine at work so will have to do it the good old fashion way with a torch haha! surely if it was anything major ide have a code stored, its not massively bad just would have thought it should be steady not erratic like it is ? thanks for your help again

Define erratic... like I said 1.8t idle is not so much lumpy but the rev counter doesn't sit steady as standard... vacuum leaks generally manifest as fairly noticeable drop in idle rpm followed by a sudden increase in revs as the ECU fights to prevent the engine from stalling... you can also check the adaption values in VCDS (block 32) to see what fuel trims are at... that can be a good indicator of if you have an airleak as the fuel trims will be out of spec

<tuffty/>

 

[<tuffty/>]

Found a video of mine at idle... you can see the needle isn't that steady...



<tuffty/>

 

[Callum Hill]

I would say its slightly worse than yours? this normal then?

 

[<tuffty/>]

On these yeah... not the best vid I realise but shows it enough there I think and thats with bigger injectors too... 750cc @4bar

<tuffty/>

 

[Callum Hill]

Oh that's fine then, ill keep an eye on it and see if it gets any worse also one last think recently my radio reception sucks get nothing on am and fm in and out all the time! ive tried standard aerial + 2 brand new ones but still poor? any ideas! once again thanks for your help been really helpful

 

[<tuffty/>]

Alas I can't really help there as I have always found radio reception to be rubbish on OE units and run an aftermarket headunit for a few years before retro fitting an RNS-E Audi sat nav unit... and the signal seems rubbish on that too lol...

I never listen to the radio... just my iPod

There are a couple of aerial amps in the tailgate (behind all the trim) as OEM units are dual diversity... its plausible there is an issue there but tbh its not something I have ever bothered to look at..

Someone else's turn lol...

<tuffty/>