okay.. so you may or may not have seen my threads around this site for boost leaks and such on my 2000 s4 6sp.. well .. i think i have found the culprit for all of my power loss and my whooshing noise. any techs out there with info is greatly appreciated.. a week or two ago i developed a misfire under load, soon after i installed my apr ecu.. i was on my way to a bonfire in the country and was about 45 min from home or so..so i continued on to the party and just drove it lightly.. but it still misfired on occasion or going up a steep grade.. then on the way home the same thing.. misfiring on occasion..so.. anywho.. got up the next day and decided to change out the spark plugs.. im a technician.. and so i didnt post anything about this(or i think not) .. i thought it wasnt a big deal since ive done countless tune ups on audis and vws.. so..did the tune up and found the culprit for the misfire.. the number 2 plug had apparently gotten some moisture in it and there was a carbon tract down the plug where it was missing..so install new plugs and bam.. misfire fixed..but.. it was soon after this that i noticed the whooshing noise on the passenger side, plus the lack of power that i thought i was supposed to have.. so im wondering.. the noise is on the passenger side, which was where the misfire was occuring.. so how long can you have an intermitten misfire occur without damaging the catalyst?? that is what my guess is to my problem.. but im not sure.. .. hrm.. now with other cars that ive worked with.. it could be missing for about and hour and clog the cat.. some cars were driven weeks with a miss and still didnt clog the cat.. so whats the rule of thumb on my s4 with an apr tune??? i had planned to gut the cats anyhow.. so my plans will just be put in motion i guess..so all of my boost leaks are fixed... as ive checked my numbers with others with an apr tune and boost levels seem equivalent.. and this would explain why the cars boost in first gear is limited .. its trying to force exhaust through alot faster than the other gears.. so its not as noticable in the higher gears.. from 1500 to 6000 in first gear probably takes 2 seconds. then from the same 1500 to 6000 in third gear probably takes twice as long.. hrm.. just trying to figure this one out...im gonna post the same in the s4 threads...

 

$.02 buy a Vag-Com! www.ross-tech.com

It really helps when diagnosing problems. Then you can use http://wiki.ross-tech.com to look up the codes and see whats going on. If your cats are kaput i would assume the post-cat oxygen sensors would also be gone and you would get code p1176 or somehting.

If the car is boosting normally it could partially be the B5 S4 paranoia (it is real!). Gutting the pre-cats and putting straight pipes in for your main cats will surely increase power make it louder and spool your turbos faster.

Ill go out today and do a few pulls and see if i can mabe hear some kind of rishing air sound

 

Speaking of clogged cats, does anyone recommend an "in a bottle" fix I can try to correct the situation. The Audi Tech said I have a clogged cat - Mine are aftermarket and would rather try a cheap fix before I go big $ replacement.

thanks!

 

yeah.. step 1.. remove exhaust from down pipe back. step 2.. get a big hammer and a long pry bar.. step 3.. beat the hell out of the converter.. beat it till it comes out.. lol.. there are no "in a bottle" fixes.. its clogged up and must be replaced or physically removed before the problem will be resolved.. and hp addict.. i was told the apr tune i have is actually a stage 2 tune and so the ecu does not even pay attention to the post cat o2 sensors.. and just because they are slightly clogged does not mean that whatever is left of them is not still doing its job and reducing emissions somewhat.. albeit not as efficiently as before...

so.. if i gut the precats, do i need to go ahead and run straight pipes for the cats further back on the exhaust?? i was told there is more restriction in the precats.. but i guess if i have a clog then i need to remove all of the catalysts.. right??

 

but then again if your cat is not clogged and just doesnt reduce emissions then just put up with the check engine light. ... well regardless of my problem.. the converters are out and tomorrow morning ill beat their guts out and have them back on to check for clogged catalyst.. someone also mentioned that due to my APR tune that i might want to go with a darintake.. to allow more air flow.. maybe thats the suction noise or rustling noise is the car needing more air flow..