So I ended up taking apart my upper intake manifold to have access to all of my spark plugs, had a friend of mine (who is a certified mechanic) clean the manifold for me while I changed the plugs then put it back together. After connecting all of the hoses, connectors, bolts and nuts back together (with a new gasket) the problem started. I noticed I had a high idle (won't go lower than 1000 RPM, even when completely warmed up), the temperature of the engine rises fast but won't overheat (in about 30-45 seconds it's at the normal temperature of a car running for a while when it used to take up to 5-7 minutes to get there) and when I'm slowing down, the high idle causes it to kinda jerk through the lower gears.

I hooked up an OBDII to the car when I got home and found 4 codes: P0455 (EVAP Emission System Leak Detected [Large]), P1448 (EVAP Canister Cent Control Valve Open), P0102 (Mass or Volume Air Flow A Circuit Low), and P0113 (Intake Air Temperature Sensor 1 Circuit High). I know in time it's going to be serious and have talked to a few people but any input will help me with this one.

 

Don't over analyze. It's probably not coincidental that the issue happened after the repair. Start with the basics. Check for vacuum leaks. ie pinched, torn, or disconnected hoses. Then check connectors. It's easy to miss a connector after having the manifold off for a bit. Are you 3.0 or 3.5?

You could even take a couple of really good photos of the engine bay and we can look with you.

 

It's a 3.5, and I'm trying to not over analyze, it's just crazy that all those codes popped up at the same time after all of that. I did recheck all of the hoses and made sure everything was connected, but I don't know how to go about checking for a bad wire since I don't know much about electric.

 

Those codes are probably all cascading from one problem. Work through the install checklist in your mind as you physically inspect each item you touched. It helps to breathe slowly and have a beer in hand while you're doing it.

Sometimes it's hard to see the forest for the trees. Take some pics. Maybe we can help with a remote visual inspection.

 

Check the FSM http://www.nicoclub.com/FSM/maxima/ for the troubleshooting steps for those codes.

-edit, P0102 and P0113 both can be caused by disconnected harness connectors or air leaks in the air intake system.

 

Make sure you properly torqued all of the manifold bolts, check the fsm but I think there usually around 9-12 ft/lbs. I over torqued the front three on my UIM(my torque wrench was so big I didn't feel the click right away), causing the back to leak and a whole sh*t load of codes to pop up.

Like the guys said, a cool head and even a beer will def help find solution.

 

I am gonna check up on that, but the update for right now is I hooked up the OBDII again and got another code (P0507 which is for idle being higher than normal) and then cleared the codes. I drove around for a while to see if the engine light would come back on or not, which it didn't for now so that puts me at ease a little bit. I'm still gonna recheck the hoses and look through the FSM. I'll take some pictures tomorrow when it's daylight and post it on here when I get the chance tomorrow.

I appreciate the help you guys are giving me so quick

 

Did you're friend mess with the throttle body? I don't know first hand, but there are lots of stories here with funky idle after cleaning maf & throttle body if the butterfly valve is moved.

 

Check the blue and green electic connectors behind the passenger side of the UIM.
Check the smaller connectors on the EVAP solenoid on the driverside of the UIM.
Check the two vacuum tubes on the rear of the passenger side UIM(brake booster and pcv connections) and one on the front of it(VIAS).
Check that torque is not to high on upper/lower IM gasket.
Check that gaskets were installed correctly

Clear codes and get back to us.

 

Didn't see where you did the idle air/ throttle body relearn.

 

You simply need to reset the ECU and do the idle relearn procedure, and your high idle problem will be gone...

 

i read stories like this all time, i have done several spark plug jobs on 3.5's and i DO NOT DISCONNECT the throttle body, i flip the manifold upside on the drivers side and i even unbolted the elbow to polish the manifold like you mentioned, but i dont disconnect the throttle body AT ALL, because of these idle problems. i do disconnect the maf sensor but i dont turn the switch back on till everything is connected