jgba8 Posted April 2, 2009 Report Share Posted April 2, 2009 i have a 2002 a8 3.7q sport with 139,000 miles FASH from new. engine management light came on and brought it to stealers. they advise that the cat on the left bank is defective and needs replaced with lamda probe as well - cost for work £1,250 please. is it possible for a cat to go defective? and should i replace the lamda probes first and any other sensors that tell the management system there is a problem with this cat before shelling out for a new cat. Also noticed the car a little harded to start when warm, engine dose not fire up properley first time, rely's on starter for 10-15sec longer than when cold. when it dose fire it idles at 6-700rpm before comming up to idle at 8-850rpm any idea's please thanks jim Link to comment Share on other sites More sharing options...
sutherland Posted April 2, 2009 Report Share Posted April 2, 2009 If you do need to change the cats (are they rattling?) and no other manufacturer produces aftermarket cats, it's worth getting an exhaust specialist to fit sports cats. I've just done that on my S8 for a cost of £400 (for two). Link to comment Share on other sites More sharing options...
sloss Posted April 2, 2009 Report Share Posted April 2, 2009 With the long cranking time a lot of unburnt fuel is entering the catalyst chamber - that's not good for it so the diagnosis may be right. You need to get the poor starting attended to or it'll happen again..... Link to comment Share on other sites More sharing options...
jgba8 Posted April 2, 2009 Author Report Share Posted April 2, 2009 Cannot hear the cats rattling. can you confirm where you got the sport cat from? thanks jim Link to comment Share on other sites More sharing options...
Goz Posted April 11, 2009 Report Share Posted April 11, 2009 Hi Jim, I got a pair of HJS 100-cell cats from Milltek-sport for £750 for the pair, admittedly a bit more pricey than Sutherlands. I was looking on Ebay yesterday for various parts from Germany and saw these, shame I didnt search on ebay before I paid £750 for new ones, may be worth a try: Audi RS4 / RS6 / S4 Bi Rennkat 100 zeller Edelstahl on eBay, also Sonstige, Sportauspuffe, Auto-Tuning -Styling, Auto Motorrad Teile (end time 13-Apr-09 10:09:10 BST) Link to comment Share on other sites More sharing options...
jgba8 Posted May 18, 2009 Author Report Share Posted May 18, 2009 Just an update of where i am. Replaced the MAF, checked all Lambda probes - all ok and hot starting problem persists. The hot starting problem only occurs anf the car is left off for 3 hours. Re starting from hot within the 3 hours is no problem. Engine managment light came on after resetting with Dealer. Problem now with left bank pre-cat. Re-set again and after 300 miles Engine light on again checked with dealer again now problem with left bank cat, pre-cat and right bank pre-cat. Dealer insists nothing else wrong with car and cost to repair £750 for each precat and cat as quoted previous. My understading is cat's generally do not fail and if they do they is another underlying reason. Intend to try the Engine Coolant Temperature Sensor to see if this sorts the Hot starting issue Will update jim Link to comment Share on other sites More sharing options...
BW2309 Posted May 20, 2009 Report Share Posted May 20, 2009 If CATs blocked they can cause too much back pressure that affects hot starting. Also, worth looking at is that the fuel pump relay on A8's can cause this very issue! Check it is clicking in when the engine's warm. Link to comment Share on other sites More sharing options...
IceBlue8 Posted May 21, 2009 Report Share Posted May 21, 2009 And cats do fail without rattling. I had the same issue with my 2.8 - engine management light kept coming on after resetting; defective cat code on the Vagcom; but no rattling. And I had trouble starting it if I'd only run the engine for a very short period (to straighten the wheels for a wash) and then left it a while before restarting. My local garage swore it was fine if it didn't rattle - until it blew! But I think he got some aftermarket cats 'cos the price was nowhere near the figures you guys are talking about. Link to comment Share on other sites More sharing options...
Alastairm Posted May 28, 2010 Report Share Posted May 28, 2010 Sutherland- where did you get your cats made as no one seems to do off the shelf ones for the s8 merci Link to comment Share on other sites More sharing options...
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