I've been working on my 2000 jeep Cherokee and I just put on the exhaust manifold but I'm waiting for an exhaust piece. But while I'm waiting for the exhaust PC come in I want to go head and start it so I did but it isn't running very good could that be because it is running out of the manifold? It will start up and run for a few seconds and shake a lot then it will die

 

So, it's not hooked up to the exhaust, which means the oxygen sensors can't read the gasses. I'd say leave it till you hook it up correctly.

 

ok I slide the old exhaust under there and plugged the o2 sensors in just so they where plugged in but they aren't reading anything. Thank you

 

O2 sensors measure oxygen in your exhaust. That measurement is sent to your engine management system to adjust your fuel mixture. If the engine ran fine before you took the exhaust off, wait to run it until you reinstall the new one. Make sure it's tight and free of leaks. Plug in your o2 sensors and then try to run it. Until then, don't mess with it.

 

yea well I've just put the engine in but it ran fine before I took it out of other vehicle it's just got me scared but I'll just wait for the exhaust to come in thanks man!