Originally Posted by uberxj92
Start with some vehicle info and background.
With those big tires on a 2.5 without knowing your axle type or the type of road its only a guess here. If you're topping out at 50 then it us safe to assume you're still stock and that's all she has to offer. I bet she has no acceleration? So thus leads to either changing gears/axles or smaller tires.
The idle issue could be alor if things. We'll need to know make model year engine transmission.
^second that we need vehicle info
also agree that 50-55 makes sense with a bone stock low output 2.5l. I have 31s and it has trouble at 65 with a head wind and god forbid a slight hill. You can put gears in it but with 35s you probably have at least a 4" lift, probably more so the drag coefficient is absolutely terrible. By the time you get gears in it greater than 5:1 you wont be going much faster than 60 anyways n ull be spinning at 4,000.
I'd check the intake for vacuum leaks. Seafoam can make that pretty obvious. Or you an spray starter fluid around every hose connection and manifold flange while the engine is running. If the idle raises shortly, you have a vacuum leak at that spot. It could also be a the sensors/butterfly valve in ur throttle body. Clean all the gunk off those. Lastly, it could be a number of other issues
Type ur problem into google with 2.5 yj/tj in there somewhere n ull proably find a thread ont he forum about it