all seems ok until it hits around 40 mph, then it's like it wants to bog down, or no power, or try to die...

Anyone have an idea?

TIA

 

Sounds like airflow starvation. Need to ask dumb questions now. What's the status of your typical/standard owner maintenance items? When was your last tune-up with air filter, throttle body cleaning, plugs, cap, wires, OBD readbacks, etc....

 

First two things that come to mind are a fuel delivery problem and a clogged catalytic converter.

1. Verify fuel pressure with a fuel pressure gauge installed on the schrader valve on the fuel rail. At idle, you should have 49 psi, plus or minus 5 psi

2. Verify that you have no exhaust restriction with a vacuum gauge. SEARCH for how to do this.

 

sounds like a cat to me

 

Picked up the Jeep a few months ago, bought it from a Geological blah blah blah company (bunch of engineers) They had to keep the maintenance up on the thing due to some codes etc..etc...

Tune-up..dunno Air filter...I took out few weeks ago and it looked fine
Throttle body cleaning...dunno plugs...dunno cap...dunno wires...dunno OBD readbacks? wth? lol

It is throwing a code, so my son is going to take it to school Mon to see what code it is. They have a really nice garage for Autotech class.

 

After doing some reading on here, I am wondering if it's not he Cat...seems like similar syptoms... would it throw a code?

I'll have my son run those test at school?

 

That's what I was thinking...

hope it's not a PITA to fix...

I see a lot of folks just pull them out..Will it pass inspection with it out? That is the only thing that would give me pause..

Thanks

 

Leave your cat alone, its not clogged. Change the fuel filter, and enjoy your XJ again.

 

would a fuel filter throw a code? engine light...

 

yes a cat will throw a code it should be p0420 catalyst efficency, and a 99 doesnt have a fuel filter, its internal

 

Nice to know...thanks..

 

put your hand over the tail pipe and have some one rev the motor if its plugged youl now

 

I'm no genius, but that just don't seem normal..LMAO

would placing a piece of paper over the pipe do the same thing?

 

a cat will usually throw a code not always. these jeeps are known for havin bad cats. usually if the truck runnin bad ruined the cat it will throw a code but if the brick is broke i see them alot without codes. we prolly put 2 or 3 cats on cherokees every moth at work. normally runs between $200-$250

 

im thinking it will be your fuel filter,and yes it would give you a missfire code of the last 3 cylinders,but not always,hope it works out good.