usmonaro

2004 GTO m6. Installed cam and 243 heads. Started the car on manifolds only and idled great with no check engine light. Put the rest of the exhaust on, installed and connected from o2's and the backs are plugged off. Now the car is hard to start, will not idle but runs fine going down the road. Have to keep on the gas at idle to keep it running. Normal? Why would it idle on just manifolds? Just wondering, car is getting tuned this coming Monday.

David Q

The back pressure and the tune are keeping it from running. Be careful driving around untuned it's probablly running lean. After a good tune it should come alive.

usmonaro

Nope. Dropped it off at my work, 1/2 mile to the shop its gonna get tuned at. I was easy driving it here.

hotjohnnyls1

It will run like **** without the rear 02s I'n.

allout06

iTrader: (11)

Rear o2's don't affect performance any.... Just the fronts.

DarkCloud

Back pressure has nothing to do with anything.. the scavenging is what your trying to get at.. IMO you changed **** around with out changing the tune.. on the newer cars they have electronic throttle bodies and such, the idle probably needs to be relearned.. and as with any serious mod i.e. cam i would get it tuned asap, you dont want to ruin anything by running it with the air fuel ratio off. Its probably nothing more than a tune issue. If there is a gm dealer in the area you could bring the car there, and try to have them relearn the idle for you.. that might at least get it to idle.

DarkCloud

The rear o2 sensors are nothing more than monitors for the cats. the fron o2 sensors control the fuelling of the car. with the rears disconnected the worst that will happen is a SES light.