Nocking sound when accelerating hard 2000 Audi

10

Asked by Nov 30, 2013 at 05:05 PM about the 2000 Audi A6 2.8 quattro Sedan AWD

Question type: Maintenance & Repair

2000 Audi A6 quattro, usa, automatic (with sports +/-)

There is a repedative nocking/thudding sound when I accelerate hard (foot to the floor) the sound seems to be throught the car as if the driveshaft was hitting (My very novice way of describing)

The problem does not happen if i accelerate at an average or slow even if i use the sports shifting and ride the gears out to just before redline before shifting.

I have plenty of tools and a decent knowlege of what to do with them.
Any help would be apreciated!
Check engine light is off and my OBDII doesnt detect any problems

5 Answers

this would indicate a LEAN condition....the EGR does engage when operating temperatures get too hot...this would cause knocking....is this problem when HOT?....am suspecting a sticking EGR valve...you might try pulling the vacuum source to the EGR and puttin' a golf tee in the suction part of that...see if this does anything....might help find the culprit~

this one still has a vacuum advance on the distributor (I think, would have to look it up) see if this exists and operates normally~

timing too far in advance can also cause this knocking...Octane too weak to do the job too can do this~

10

Thanks for all the help! Ill be sure to test your ideas, in answer to your question, i would hesitate to say it was in hot temperatures, i'm currently running the car in freezing temperatures (floating around 32) in the mountains of Colorado. Something to note, the knocking does not happen if i am sitting on the driveway in neutral/park and revving (as if i where when i hear the knocking) Would the EGR only be operational when in gear/driving?

635

Check drive shaft going to rear diff' most likely the carrier bearings on shaft are going bad, they are mounted in rubber mounts, just did a 2007 ford fusion all wheel drive, sounded like the bottom of car was trying fly apart when going down road, but not make a noise sitting in driveway, you. might have to put it on hoist to check for sure, EXPENSIVE.

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