Bogs At 2300+ But Under 2300 Is Smooth

[Oddmodman]

Hey guys this is on a '90 Cherokee 4.0 ax15. No not an MJ but has the same engine... Anyway, as the topic states, this engine starts bogging, though doesn't die, starting at 2300 rpm. It'll only get to about 2500 rpm max. It starts fine and runs very well, as long as it's under 2300 rpm. Once I do peg 2300 and this happens, as soon as I let off the pedal it runs just fine, doesn't skip or anything on its way back down the rpm range.  Does it in neutral, and does it under load. I don't think it's the cps, as I pulled and cleaned it, and it revs up great til 2300; doesn't make sense to me that the cps would be that picky, though if you know better, please inform. Possible other culprits that I can think of are cat, tps, throttle body(?), fuel pump sock, fuel filter, injectors(?). What do you guys think?

[Eagle]

Clogged catalytic converter?

[ride172]

Tps might have a dead spot wore into it. To test use an analog volt meter and watch the needle as you slowly manipulate the throttle.

[ride172]

The needle should have a smooth arch

[Keyav8r]

I'm with Eagle on this. Had a Chevelle once that did the same thing. If you still have a catalytic converter on the truck, unbolt the connection and tie it off well so you can start and drive the truck. If it is the converter, the truck should run normally with it disconnected. Normally, but loud.

If it's not the converter (or you don't have one), no clue.

[Oddmodman]

It does have a converter. I'll give it a shot today. I'm also having dad pick up a fuel filter; cheap enough to chance. I'll also have to see if dad has an analog voltmeter, cuz I know mine is digital. When a cat is bad is there any visual clue as to its status? Like water dripping, some particular color of smoke or anything? Thanks for your input guys, glad I have a place to start  :thumbsup:

[gogmorgo]

There's so much heat shielding on the cat that it's really hard to tell what's going on from the outside. If you pull it off and look into it, it could be visibly clogged, but it's the same amount of work.

Unless you get e-testing in your state, you could just put in a straight section of pipe. If it's just a visual inspection you may be able to get away with just putting a hole through the core and putting it back, but you'd never do that cause it's highly illegal, eh?

[Oddmodman]

A) No inspection. I think Alaska's probably got the cleanest air in the US. B) I'd probably go get a cherry bomb to replace it C) When the law is stupid, I don't mind breaking it  :USAflag: . 

[Tactical Bacon]

The Supreme Court has ruled that unconstitutional laws have no legal weight. Though, good luck telling that to the ATF if they find you with an unregistered DIAS. >.> <.<

[Oddmodman]

I fixed it!! It was indeed the cat. The cat-to-downpipe bolts I couldn't get out because I couldn't find a wrench to fit them - bigger than 13, smaller than 14, bigger than 1/2, smaller than 9/16; probably just rust-warped. So I divorced the cat from the muffler, and sure enough, exhaust was packed with converter chunks. Since I couldn't just drive a hole through it, I used long needlenose pliers and pulled each chunk out. Some were too big so I had to crush them into smaller chunks. All in all it took about 45 mins to clear out. Thank you everybody for your help! She revs like a demon now  :clapping: . PS, I just reattached it and I'm leaving it alone since I'm selling it anyway. Once I get rid of this I'm one step closer to being able to work on my real project: fixing my  . :MJ 2: .