1996 Grand Cherokee 4.0- wont go over 2000 rpm

[Kuato]

Burned valves aren't likely to happen suddenly. OP said it ran great a few weeks ago.

Any update?

 

[artificialist]

Sometimes the cat doesn't fail, but the backpresssure rises for a different reason. Sometimes the insides of the muffler fall apart. Do you drive where there is frequent cold weather and you have long warm up times?

Anyway, I say check fuel pressure, then exhaust backpressure.

Not all cats fail due to an engine running badly. Sometimes heat cycling and vibration can be bad enough to make it fail.

 

[meep]

Originally Posted By: Kuato
Burned valves aren't likely to happen suddenly. OP said it ran great a few weeks ago.

Any update?


correct. burned valves would sneak up over time. good catch.

Originally Posted By: rslifkin


I doubt this is the issue. Usually a valve sealing problem would be worse at low rpm and it would run better at higher revs (less time per cycle so less leakage occurs).


not neccessarily. the preignition and detonation that occurs from the hotspots on the valve are equal opportunity and will eventually reach a point where on level ground, regardless of gear and rpm, the engine will not keep the car rolling... and feeding it more gas just makes it worse.

Hopefully this isn't what the OP is experiencing. I actually agree that the first place to look is plugged exhaust.