Hello im new here lol, so anyway my auntie gave me the Maxima, but she said i need to replace the rear valve cover gasket. I was successful on putting the new gasket on but not such a great job on putting it together.... Ever since i did that now it dont stay started it starts!! but it dies out right away Can someone please help!!?? When i first brought it to my house it ran fine like it started no rough idle but now idk

 

Did you remember to reconnect the MAF? What about other connections? Either it's a simple fix and you forgot to reconnect something or you have a massive air leak. Time to retrace your steps.

 

Well my moms mechanic came by yesterday and he was feeling the back side of the manifold and said he felt air coming from under neath... But i dont recall taking a hose off underneath the manifold except for the egr coolant hose i did connect all the connections back. heres what connections i took off
MAFS harness
some other harness that went on the air box housing
The 4 connections on that 3 bolted thing idk what its called
3 Ignition coil harnesses
the 2 grey and orange harnesses next to those 4 colored ones
umm thats it

 

Again, you're gonna have to retrace your steps.

Since the mechanic detected an air leak, that is your major clue right there. Make sure the upper intake manifold (UIM) is seated correctly. Confirm that you re-installed the EGR gasket at the back of the manifold. Hopefully you installed a new UIM gasket at the same time you re-installed the manifold, as those dry out over time, become hard, and aren't meant to be re-used and can cause air leaks. Did you tighten the bolts to the UIM in the correct order and to torque spec? Did you tighten the rear valve cover bolts in the correct sequence and to the correct torque spec?

If all that checks out, you're gonna have to pull the UIM again to re-check and re-seat it. Re-check your rear valve cover replacement work too. Did you put RTV in the corners as described in the Factory Service Manual (FSM)?

 

No i havent replaced the uim gasket and also i did install the egr gasket in the rear of the IM i didnt put any silicone on the gasket when i put it on i did put them on in the right order

 

get a new upper intake manifold gasket. Then install it. NOTE the fellowship pro box will have more gaskets in it than you need. Just use the one which matches the one which came with the car.
Clean the mating surfaces well. Do not use gasket sealer. Tighten the bolts with a torque wrench