I have a 91 xj 4.0. I took it up a real steep hill today in 4 high third gear it's automatic. Well I had to nail it about half way up and it only hit about 2,000 rpm. Any one ever had this problem?

 

My 89 bogs down on every hill I hit. The renix engines like mine have even less power then the H.O. like you. I would just check your plugs and all that. Do a tune up, maybe seafoam it, run an octane booster or a higher grade fuel through it for one tank. having it in 4hi would also add to it bogging down. The more tire to spin, the harder on the engine it is. You probably shouldn't be in 4th gear in 4wd anyway. I would stay under 30mph just to be safe. 35 tops. It puts a lot of strain on the components. Especially on pavement.

 

Sorry, forget that last part. Didn't realize you said 3rd gear.

 

I have a new cap rotor plugs wires throttle body spacer I did seafoam and I run lucus octaine boost and 91 octaine gas all the parts only a month old

 

Damn, I don't know then. Maybe a clogged cat? Did you test the throttle position sensor? It could be the transmission not registering to downshift also.

 

It's straight piped. TPS I think it would bounce around a lot I got one on another xj I'll swap and see. I'm more thinking tranny now on the highway it kicks down a lot from overdrive so Mabe it's not working right in 4x4

 

It could be somethin with the 4x4. Maybe its not moving free enough. Have you changed all the fluids recently?

 

Did the tranny shift down? In that situation I would thing the tranny should have shifted to first (depending on your ground speed). If it never shifted that would explain the low RPMs and lack of power.

 

I haven't took it back out due to I pulled rear end out to put 4.5 leaf springs in :-) I'm kinda thinking I might just have a worn out motor because like on high way it's always kicking down like I'm not making enough power to keep it at speed

 

8 horsepower less at higher RPM and the same torque throughout the range.. Renix is just fine. Don't drink the HO Kool-Aid.

 

Guess I'll have to post a video of me and my buddy racing. He has stock tires and no lift so I think he has the advantage. 10 cars hardly seems like an 8 hp difference but I do have a 98 with 5 more ft/lbs of torque I'd say the TPS is the hill climb problem

 

Yeah let's see the video . I don't think I have a HO. I could be wrong. I have not changed the trans fluid because it's looks good but all others have been changed and ran seafoam too. I got to get that TPS switched out will that make it kick down a lot ?

 

Alot, no. Like it should, yes.

 

Humm ok

 

If you have a 91 then you have a Hemi Output lol