Rough Idle, some suggestions please?

[mcandmar]

AAN 90k miles, intermittent stumble on idle, sounds like 4 1/2 cylinders, seems to come and go at random. Also has a hesitation at 1200rpms and 1800rpms, like a small miss but it’s always there.

Cant find any leaks but i dont think were getting full boost, today i was getting 1.9bar on the onboard computer and twice i managed to get 2.0bar. Anybody know what i should get with a urs4, stock chip?

So far i have changed, O2 sensor, Spark Plugs, Coil Packs, MAF, and checked for airleaks over and over. After changing the coil packs the problem went away for 2 weeks then came back again.

No fault codes, only thing odd is the lambda value with the vag com constantly fluctuates when the engine is stumbling, values jumps around from 960, 1020, 980, etc etc, only sits a steady 1000 on overrun.

I have a complete ABY engine so i can change bits out to test, i need some more suggestions to try

Thanks,

Mark.

[Corey]

Air leak or your spark plugs are not tight. You should see a maximum of 2.2bar (indicated on the gauge) of momentary overboost but not in all gears only under heavy load in 3rd/4th etc.

[mcandmar]

Ok were getting somewhere, pulled the coilpacks again and re-torqued the plugs all ok, i noticed one of the rubber leads (from coilpack to plugs) was torn so i changed them out for my spare set and what do you know the miss is gone

Also changed out the WGFV and DV but still only getting 2.0 max. 4krpms in 3rd with WOT sits at a steady 1.9bar, will have to get under the car and check out the intercooler and hoses now, at what rev range do you see 2.2 bar?

Thanks,

Mark.

[Jas11n]

Check throttle cable is tight. Ben ("Lune" on here) had this on his urS4, Nothing could be found to be wrong, just car wouldn't get overboost. Cable was slack causing WOT to be "not - so - WOT".

Just a thought.

[mcandmar]

LOL that something i would never think to check, i'll have a look