ok here goes i have a 2001 a4 2.8 quattro 5spd with aprx 90k on itandin the past say 2 weeks i have started noticing a little engine stumble at idle and a slight flux in the idle, feels a little bit like a misfire but not a dead mis....so i changed the spark plugs and wires as thats part of the 90k anyway, still there...thing is it goes away when u rev the car and it isnt always there...ill be sitting at a light and only feel it after sittin there for 30 seconds sometimes...sometimes its constant and then there have been like 3 days i havent felt it at all....no check engine light and when i checked for codes the only codes that came up had to do with the warm up for the cat...i have since cleared them and they havent come back in a lil over 200 miles, could the cats be the issue? i was also thinkin maybe a slightly colgged imjector? any1 experience this? am i on the right path? thanx in advance and great sight

 

What kind of gas do you use?

 

always either sunoco 93 or mobil 93 but always 93 octane for as long as ive owned the car

 

possible fuel filter. Maybe not enough gas a idle the when your giving it gas the engine is getting enough.

 

If it was a fuel delivery issue i would suspect a dirty fuel injector or fpr problem before the filter. Since its such an intermitent/mild issue it could honestly be too many different things to pinpoint the problem over the internet. Good luck.

 

Did the dealership due the 90k? Are they the correct spark plugs is really what I am asking. If they are try running a good fuel injector cleaner through the system and possibly a bottle of heat if it is really cold where you live. A slightly clogged injector will drip at idle then spray at higher rpm causing a misfire or major misfire at idle (the computer will not recognize all misfires they must be bad enough for the knock sensor to pick them up). Bad or incorrect spark plugs will also cause a misfire at idle without codesand will go away at higher rpm.

 

changed the plugs myself and bought them from the audi dealer....they r good....now i dont think it catches a misfire from the knock sensors should catch it from metering the rotation of the cam vs the crank based on those sensors and either way im not gettin a misfire code for any cylinder

 

Ya sure, believe what you want. I would suspect the feul injectors.

 

gues ill just have to stop being lazy and pull te fuel rail this weekend and test each injector....damnit really didnt wanna devote my saturday to that............will let u guys know how i make out

 

If you have a Vag com or some other means of data logging you can see the percentage of misfire in each cylinder, even if there is no code sometimes a misfire is present and can be seen with an active test. I would try to find someone in your area with a Vag com or purchase one if you don't have one. Data logging will tell you for sure if you engine "stumple" is a misfire.