losing power

Not sure if this belongs here, but I'm at a loss.

My jeep seems to not have any power anymore.

it lacks any kind of get up and go around town, it can't get out of its own way on the highway if there is any kind of incline involved.

when wheeling, if it gets bound up bad enough it simply will not put power to the wheels, I can be foot to the floor in 4 low and it will not rev beyond 3k and the tires won't even turn if they are badly bound. it struggles to climb steep hills in anything other than 4low.

other than that, it will climb in 4low just fine.
plenty of engine braking, I had a compression test done a few months ago and I don't have the numbers anywhere but it was perfect.
does not burn any oil.
it runs a little warm at times but not anything I would be concerned with.

specs:
99XJ. 4.0. AW4. 210k miles
35"s. 4.56 gears
Brand New magnaflow Cat (thought the old one was clogged)
Magnaflow 24" glasspack muffler
AEM CAI
4640lbs trail weight.

I really thought swapping the Cat would do it, but no change.

also, random note: the exhuast has a strange whistling noise under load. sounds like a turbo spooling out the tailpipe, but only under load. it won't do that sitting in neutral.

thoughts?
things to look for?

Head gasket?

PhotoJared said:

Head gasket?

Click to expand...

no coolant in oil or oil in coolant.

rockclimber said:

no coolant in oil or oil in coolant.

Click to expand...

That's not the only symptom of a bad head gasket. It most commonly blows out between cylinders.

PhotoJared said:

That's not the only symptom of a bad head gasket. It most commonly blows out between cylinders.

Click to expand...

compression is good.

never misfired.

Idle's smooth.



I'm not saying it can't be that, but it hasn't exhibited any symptoms.
any other tests that would show me without pulling the heads?

If it idles fine. My first test would be fuel pressure.

GordoSmasho said:

If it idles fine. My first test would be fuel pressure.

Click to expand...

good call.

I've been meaning to do a fuel pump for a while, the check valve is gone on mine.

Any kinks or damage in the rest of the exhaust system? Pieces from the old cat get stuck in the muffler?

foxwar71 said:

Any kinks or damage in the rest of the exhaust system? Pieces from the old cat get stuck in the muffler?

Click to expand...

I don't think so.

the muffler is just a glasspack, when I put the new cat in I put a flashlight down there, there didn't seem to be anything.

everything else is basically a stock XJ exhaust pipe. I am curious as to why it sounds like I have a whistle tip though.



here is a fun video yesterday of me getting pissed off because it simply will not generate power.

the rear tires are pretty well bound in the rocks

https://www.youtube.com/watch?v=yFf20u2luf4

A cracked header can screw up the O2 readings.

I say fuel pump or regulator. Test pressure and see if it holds and for how long.

My wrangler would only reach around 2500 rpms at around 20 psi of fuel . it was in tank regulator with no return line . sucked kinda for diagnostic. Thought it was regulator turned out it was fuel pump. But still got almost 300,000 miles from that pump so cant complain about that.

old_man said:

A cracked header can screw up the O2 readings.

Click to expand...

I havent seen or heard any cracks in the header, but it does have a small leak right at the front of the manifold where the flange is warped.

been like that for about 60k miles, this problem is more recent. \

I always figured the leak would burn out the gasket, but it hasn't so I haven't bothered to swap it.

Do you have a video without the music so we can hear the motor?

Mach2nh said:

Do you have a video without the music so we can hear the motor?

Click to expand...

yea, the uploader changed it. I'll try and get the original.

Wide open throttle the ecu is not using the 02 sensor . im assuming when it losses power its at WOT .

Sounds like its power is maxing out at alot lower than wot. I had a similar problem. It would run and idle just fine. Just ran out of power at about 75% throttle. It steadily got lower over time. Tested fuel pressure and sure enough. 35psi at idle. And it would drop as i increased throttle.

Cracks in the header can be darned hard to hear if you have a glasspack on it, they aren't always loud and obvious.
That said, I think the most likely candidate for what you are describing is a fuel delivery problem.
Check the lines visually for any damage.
Check the fuel pressure with key on, make sure it pops right up to spec. More importantly, though, run the gauge onto the windshield and tape it in place. Close the hood, and duplicate the problem: floor it and while she refuses to move out properly, observe the fuel pressure. If it's more than a couple pounds below spec, you've found your problem.
Again with the "most likely" but I'd suspect fuel pump problems.

Should be unmolested video

http://youtu.be/aBlocFtJCaA

reving 3K WOT without movement at the wheels means the tranny is taking some abuse, even if your down on power. Might be time for a swap/rebuild.