Headers and O2 sensor

Pete931

Just installed headers on 2002 Nissan Altima 2.5l. Car start only with no upper O2 sensors in header . Once I put it in to header car won't start. Any idea how to fix this problem ? Spacers for sensors are not making any difference. Maybe reset ECU ?

thecardoc3

Can you slide a bore scope into the header and make sure that it was made correctly? There might be something in there blocking the flow of the exhaust.