A3 8P 1.6i (102hp) rpm vary while idle

[Milos27]

Hello everyone,

I have Audi A3 8P 2003 1.6i 102hp, with engine code BGU.

Since I've bought car, I've been struggling with some issues regarding car rpm vary while idling. What happens is sometimes, doesn't matter if engine is warm or cold, rpm starts to vary.

I do have LPG in my car but everything is fine with LPG system because same thing happens even if car runs on petrol.

Now, problem is next: 

Depending if i run it on LPG (idle is around 600-800 rpm) or petrol (around 800+- rpm), rpm may start to vary. It can happen from time to time in traffic also. If car runs on LPG, rpm can raise to 1000+ rpm and fall down back to 600 or so within a second. Same scenario with petrol, only a bit higher rpms (800 to like 1500+- variation). Worst thing that can happen is after few variations, car simply dies and after next car start, it seems to act "normal". What I've noticed is while idling, that plastic manifold pressure is raising drastically when rpm start to vary. Everything happens within second. I did not realize in what actual moment it happens..

This is video from youtube (not my video), and this person had same problem: AUDI A3 1.6 IDLE PROBLEM!!! REVVING ITSELF

Difference between situation from video and my own is that he does have 1.6 FSI while I have more simple version 1.6i and my car does not show any errors codes (on diagnostics) or lights on dashboard (no engine light, epc...), everything seems fine. 

Cheapest things that I've done so far with no success:

1. I tried to clean my EGR valve,
2. I tried to clean MAP sensor,
3. I tried to clean throttle body 

None of above helped. Now, before I waste 100 Euros +- on new EGR, I would like to try something else that is cheaper fix, because I'm not sure if it's actual EGR or MAP sensor or something else...

 

Please if you have any suggestion for me what should I try or replace that is a bit cheaper (for start), let me know. I will start from more simple things, then if necessary I will buy more expensive stuff.

Thank you for help in advance!

 

[cliffcoggin]

One possibility is a faulty spark plug which might cause the revs to drop so low that the anti-stall boosts the revs briefly to compensate, and you end up with unstable idling. That is a total guess but has a cheap solution.

Another possibility is an air leak somewhere in the induction system. It might be hard to find if it is more than a split hose or loose connection.

[Wilmo]

Hi Milso27

I'm not a mechanic but my car suffered from similar issues plus jerky acceleration. Solved with 'new' brain (ECU). 

[cliffcoggin]

Thanks for posting that William. It might help others with a similar problem. It's a shame Milos has not commented further on his problem.

[Milos27]

Sorry for not replying, I had some stuff going on IRL 🙂 . Btw, thanks for replies. I've checked spark plugs, they are all fine.. Still haven't figured out what is causing this problem, it either can be something major or something very minor and stupid. Hopefully, I will resolve it soon... I'm open for more suggestions tho.

 

I will keep you guys updated more frequently in future. Thanks