range rover running lumpy :(

[monster sj]

hi guys, me stepdad has a range rover V8 3.9, he did have a loud exhaust on it, and the range was running perfectly fine, but due to new tyres he had to change it to a standard system as the exhaust was rubbing off on the tyres , ever since he has changed the exhaust the range has started to run lumpy  :(, has any1 got any ideas of what it could be? thanks

[Range Rover Blues]

Hmmm, just the exhaust?  try disconnecting the battery for 10 minutes and see if that does 'owt, it will reset the learing function on the ECU.

Otherwise what about exhaust header gaskets, check they are in right.

[JIMBOBLY]

this might sound stupid mate,but if the exhaust was loud,was the lumpyness their before,sometimes with a loud exhaust you cant hear a missfire or anything,due to being loud,i would imagine the exhaust would be bigger,being bigger it would slightly lose back pressure and run a little bit richer,have the lamda sensors sooted up,if it has them obviously,i know if it has got them they should adjust but it will still run a little richer,also if the ecu is paying up,it might not adjust its self at all,hope it helps mate :D

[monster sj]

this might sound stupid mate,but if the exhaust was loud,was the lumpyness their before,sometimes with a loud exhaust you cant hear a missfire or anything,due to being loud,i would imagine the exhaust would be bigger,being bigger it would slightly lose back pressure and run a little bit richer,have the lamda sensors sooted up,if it has them obviously,i know if it has got them they should adjust but it will still run a little richer,also if the ecu is paying up,it might not adjust its self at all,hope it helps mate :D

no mate it was definitely running fine before we took it off, we had a krypto-tune guy come round and check it all before and it was running sweet as a nut but i will try what you said, thanks guys  :D

[Rossko]

IF this one has oxygen sensors they might have suffered in the change - they are sensitive to shock

[300TDi Disco]

Can it breath properly? meaning have the baffles gone in the exhaust. A pal of mine had a problem with it running cra* because the baffles had collapsed in the end can. Something to check.