Novak Conversions Jeep Wrangler YJ engine mounts

1990 2.5L Wrangler Exhaust Issue

B

Bowie1

New Member
Joined
Nov 10, 2025
Messages
5
Location
USA
1990 Jeep Wrangler, 130k miles.

Runs and idles fine to start but after 10-15 minutes or with any uphill acceleration starts to buck and eventually cuts out.

Exhaust comes weakly out of the pipe. Local mechanic suggested it could be the carburetor, catalytic converter or muffler but couldn’t discern which one.

Are there any tips to finding out where the leak in the exhaust chain would be? I’m considering replacing part by part starting with the carburetor.
 
258 or 2.5 or 4.0? I cant recall on the 90 YJ's. Does it sound like it has an exhaust leak? The exhaust manifolds on the 4.0's are notorious for cracks at the Y, muffler wont affect diddly but noise. If the mechanic cant tell between the muffler or carb why it wont run right, find a new mechanic.....seriously. A plugged cat can be killing power. The carbs are pretty crappy IMO, if its a 2.5, the early YJ 3 year use only TBI injection is problematic as well. Sounds mostly like a fuel delivery issue, but hard to tell over the computer. Need more details.
 
Gilaguy23 said:
258 or 2.5 or 4.0? I cant recall on the 90 YJ's. Does it sound like it has an exhaust leak? The exhaust manifolds on the 4.0's are notorious for cracks at the Y, muffler wont affect diddly but noise. If the mechanic cant tell between the muffler or carb why it wont run right, find a new mechanic.....seriously. A plugged cat can be killing power. The carbs are pretty crappy IMO, if its a 2.5, the early YJ 3 year use only TBI injection is problematic as well. Sounds mostly like a fuel delivery issue, but hard to tell over the computer. Need more details.
Click to expand...

It is a 2.5L. No major noise issues. Not sure what exactly an exhaust leak sounds like, although there is some odor coming from the undercarriage.
 
Bowie1 said:
It is a 2.5L. No major noise issues. Not sure what exactly an exhaust leak sounds like, although there is some odor coming from the undercarriage.
Click to expand...

Rotton egg smell? That can be linked to a bad Cat converter. Smell hot also once it starts to act up after pushing it a bit?
 
A bad cat may cause exhaust smell.. but typically not associated with the issue you described.
I agree.. try another mechanic.
Sounds like a fuel issue.. running lean.

Try the easy and low cost stuff first
 
  • Like
Reactions: Bowie1
Unless changed you have one of the few year YJ's that came with a TBI fuel injection system on the 2.5. Not much support for that system however I see rockauto does have some of the TBI parts. Check your fuel pressure. I could see a bad coil doing this but they rarely go bad in my experience but hey, its a chrysler/jeep product.
 
  • Like
Reactions: Bowie1
Gilaguy23 said:
Unless changed you have one of the few year YJ's that came with a TBI fuel injection system on the 2.5. Not much support for that system however I see rockauto does have some of the TBI parts. Check your fuel pressure. I could see a bad coil doing this but they rarely go bad in my experience but hey, its a chrysler/jeep product.
Click to expand...

That’s what I keep finding is that it’s not a typical carb. I intend to get some carb cleaner and test for vacuum leaks. Start there and see where it takes me
 
  • Like
Reactions: Gilaguy23
I suppose if it worked Ok then go with it. The Howell FI kits are off a 4.3 TBI chevy engine so not all is lost. But being they only got used 3 years IIRC, there not real popular.
 
how long has this been going on? when the last time you changed fuel filter? last time it was tune-up ?
 
Took off the air intake and saw that the throttle valve was visibly wet on top with gas.


Could be fuel injector or the throttle body. I’m going to spray TB cleaner and see what happens.
 
my exhaust manifold on my 91 2.5 had major cracks on the underneath side. you can't see or feel them unless you remove the manifold. after I replaced it , it runs so quiet I can sneek up on people with it running. replacements at Napa $100 bucks +/-. Change the freeze plugs while your in there.
 
Novak Conversions Jeep Wrangler YJ engine mounts
Top Bottom