bouncing idle

[mat white]

car is idleing between 740 780 rpm shown on vagcom can feel the car reving up and down.
ive changed/checked all breather pipes under inlet manifold fitted new plugs fited new coilpack wireing loom changed thermostat new green water temp sensor ive got no fault codes anything else i can check for. unpluge maf also still happening.

 

[iR8V10]

Sounds familiar!

http://www.audi-sport.net/vb/a3-s3-forum-8l-chassis/162513-reasons-slightly-lumpy-idle.html

 

[jezzy]

try cleaning your maf. halfrauds sell electrical contact cleaner 3.99.

 

[meerkat]

clean and re align throttle body maybe

 

[mat white]

forgot to mention ive cleaned throttle body and reset also cleaned maf but it acts the same as withe it pluged in

 

[Paradox1]

Check your vacuum lines and also boost. I have a tricky one on my golf,there was a split on the pipe between the hard pipe and pancake pipe

 

[jezzy]

drive the car with the maf unplugged.
is it better?
From what ive read if its the same your maf is fecked.
But im no expert and try the search button and look for maf

 

[meerkat]

just another thing have you cleaned the egr could possibly cause idle problem if sticking though id probably say issue with maf or throttle body if no leaks anywere tbh

 

[mat white]

what rpm should idle normaly sit at on the s3 is it 900rpm have read somewhere else tonight to check injector o ring/seals. also how does the hockey puck part of the breather system work does that also have a valve in it?

 

[jezzy]

And one last thing to check is the wiring connector on the throttle body (bottom one) check its not lose or wiring bad.

 

[jezzy]

840 mine is on vcds (s3 and stays steady)

 

[mat white]

cool il have a look at that in the morning can any of the electronics on the throttle be changed behind the black plastic cover.

 

[jezzy]

ive been told to leave the the stuff behind the black plate alone.
But im sure someone will be along shortly to correct me

 

[mat white]

opened it looked and shut itagain lol wont touch anything in there cleaned throttle body again revs still bouncing runs fine for first minute or so then starts its never straight away even when starting from hot took injectors out tonight checked o rings all good no leaks there. been radinga bit more on the net and think it might be a dogy 02 sensor maybe?

 

[mat white]

after reading a fair bit on the net found that the 02 sensor pre cat lamba sensor can get lazy and responds slow to change causing lagging info to the ecu mine ran fine for the first 10 seconds after a start from warm then started bouncing from 720 760 rpm after unpluging sat perfect at 800 rpm going to fit new sensor tonight