Lack of power in 90 YJ
 

Hi everyone! New to the forum and posting my first question. Just picked up a 2.5l 1990 YJ. It is stock except for a 3 inch lift and 31 inch tires. It's got a new exhaust system from the manifold back, new computer, new gas tank, new tie rod ends. The body has also been fully restored. My problem is that fourth and especially fifth gear seem to be totally useless. There is no power while in these gears. And it's twice as bad if I'm on even a bit of an incline. I don't see how I'll ever be able to hit 100 kph on the highway.

Any ideas?

Re: Lack of power in 90 YJ
 

Anybody have any ideas?

Re: Lack of power in 90 YJ
 

Hey Eddie,
How fresh is the engine? Could be she's just getting tired....In 5th gear with a 4 banger, you won't see much "power". Might have to play with the gear shift a bit more.
Peter

Re: Lack of power in 90 YJ
 

Hi Peter. It's the original engine from 1990. And when I say lack of power, I mean that in fourth, and especially fifth, I'm not even able to maintain a constant speed. It's like the rpm drops way down and I start to loose speed fast.

Re: Lack of power in 90 YJ
 

Hey Eddie,
I know next to nothing about the specific 2.5 BUT from my generic knowledge, I reiterate, she could just be getting tired. That being said: New computer? Has it been re-flashed to match the vehicle? Are all your vacuum lines hooked up properly? Has she had a recent tune-up (plugs, ignition wires, PCV valve, air filter, timing...etc.)?
Do valves need adjusting (don't know if this is do-able on your engine)?
I understand your lack of "power" but a not too badly worn engine in good tune should be able to maintain 100km/hr in at least 4th I would think
Hope this helps.
Peter

Re: Lack of power in 90 YJ
 

ya sounds to me like it might be in need of a tune up, how many km are on it? could also be the 31's holding you back a little to

Re: Lack of power in 90 YJ
 

There are 191,000 km on it.

Re: Lack of power in 90 YJ
 

I thought I read something about a similar lack of power being caused by a catalytic converter replacement. I just replaced the entire exhaust system, including the cat. Could this be causing the issue?

Re: Lack of power in 90 YJ
 

I had the 2.5 in mine and with the 31's 4th was ok but 5th was only usable on flats or downhill. When I put the 33's on 5th was non-existent and it was hard to maintain speed in 4th. The 2.5 is fine for stock tires but anything bigger and it just can't do highway driving anymore. City and trail it works great but forget the highway. I just did an AX-15 and Vortec V6 swap in mine and it's like a whole new vehicle. I can hold highway speeds and even accelerate to pass in 5th gear again.

Re: Lack of power in 90 YJ
 

I have a friend in fact he's a member on this site that had a 92 yj 4 cy 4.11 gears std. and on the hwy he couldn't get to 5th gear, after he put his 33" boogers on. The fuel mileage sucked about the same as a 6cy. Its the motor that just doesn't have the guts. Not much you can do but live with it, unless you put in a bigger motor.