trying to figure out a power loss problem

    ok, I've been fighting with my XJ for almost a year now... trying to figure out why it doesn't have any power. When the motor started knocking and found out that it had a cracked piston, I figured that was the cause. NOPE! While there is more power than before, it doesn't have enough power to accellerate up a hill, beat a Neon to the speed limit, whatever. I can maintain a speed on a hill now... but that's about it. Something weird is that it seems to have more power at partial throttle vs full throttle. I've got a thread going on NAXJA, if you want to see everything I've been doing. http://www.naxja.org/forum/showthread.php?t=970363


    Basically, I've checked/replaced the TPS, IAC, plugs, injectors, fuel pump, rear catalytic convertor, transmission, brakes. I haven't replaced or disconnected the front 2 catalytic convertors at the header, but a vacuum test leads to believe that they are not clogged. It's not misfiring or throwing any error codes. Timing was checked/adjusted when the motor swap was done. I was kinda almost thinking that it's just because I have big tires, but I rode in a YJ with heavier tires (and high gearing) and it has the power I remember mine having when my XJ was stock.


    Any thoughts? :?

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    plugs aren't the problem, the normal recommended Champion Truck plugs, #4412. Was using them months before the power loss started last summer. The new motor has a fresh set. I wish it was that easy. :)

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    Edited once, last by whatevah ().

    Quote from whatevah


    plugs aren't the problem, the normal recommended Champion Truck plugs, #4412. Was using them months before the power loss started last summer. The new motor has a fresh set.


    Well, I know you swear by those plugs, but there are many others that swear some Jeep motors don't do well with them.


    What all did you use from the original motor?

    I've never know anybody to have problems with them. Only people who use the fancy triple-v-spark platinum stuff. It's not misfiring or anything like that, though. It idles and runs smooth, it just doesn't have any power.


    fuel rail + injectors, spark rail, alternator, a/c condensor, steering pump, intake/exhaust... only new stuff is the spark plugs and water pump.

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    if you have access to a scanner check the intake air temp another indicator of converter issues,also have someone throttle it and feel the exhaust at the tail pipe if its extremly hot or you hear any hissing could be cat conv.also is it auto trans and starting in low gear and or is it down shifting on acceleration.just for kicks recheck the fuel pressure with a guage

    I have a scangauge, intake air temp is around 150ish when motor is at operating temp. Sensor is inside the intake manifold. Exhaust temp is about normal. Auto trans, shifts normally.

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    I'll recheck fuel pressure tonight.

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    well jerry you could always run a blower on the 4.0 they make them now and maybe for a little more power add methanol injection ;D

    have you regeared? i did not see if you have changed it on you profile.

    .,=======o00o<br />//__|__l__,\___\,___<br />l_---\__|__|---&#91;]lllllll&#91;] _<br />(o)_)____(o)_)--o-)_)__

    Any engine codes? Perhaps the check engine light is burned out... and you have codes sitting out there. Have you checked the gas mileage?



    Steve

    Nobody belongs anywhere, nobody exists on purpose, everybody's going to die. Have a beer.


    Jeeps Owned... 89YJ, 81CJ-8, 99XJ, 93XJ, 00WJ, 05LJ, 22Bronco Badlands !

    Quote from rstiles


    have you regeared? i did not see if you have changed it on you profile.


    He's running a different 4.0L now. He had the same set up with his old engine and the old motor had more power.


    Did you check the MAP sensor yet?

    Member since 2000

    Jeeps Owned'79 CJ5:

    Specs-

    - 258 I6

    - '93 Cherokee fuel injection and HO head,

    - bored 30 over

    - with 4x4 cam

    T18 tranny with granny low / Dana 18 t-case

    Dana 44 front and back from late '70s Wagoneer, both locked and loaded with 4.88 gears

    SOA on modified YJ springs with shackle reversa

    Fiberglass tub with 6 point cage mounted to the frame


    2015 Grand Cherokee Limited
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    Quadratec Floor mats

    no he said its been a year he has been fighting it he just had the engine replaced and there is still a problem

    .,=======o00o<br />//__|__l__,\___\,___<br />l_---\__|__|---&#91;]lllllll&#91;] _<br />(o)_)____(o)_)--o-)_)__

    Quote from rstiles


    no he said its been a year he has been fighting it he just had the engine replaced and there is still a problem



    x2




    He couldn't keep up with my TJ on 33s with 3.07s. I hope you figure it out Jerry!

    You do own a hairdryer don&#039;t you she asked? Of course I do, he replied, it&#039;s in the driveway, it&#039;s called a Jeep.<br /><br />Current - 97 TJ, 99 WJ, 12 Scion tC<br />Past - 94 ZJ, 02 TJ, 06 Rubicon, 06 XK, 07 Scion tC

    Jerry can you read fuel trim with the scangauge, sounds like its leaning out. When you check the fuel pressure drive the jeep under load to see if the fuel pressure drops off when you loose power.


    Also if you still have the vacuum gauge check the vacuum under load while driving and see if it drops off.

    MAP sensor seems to be working correctly. I can watch it on the gauge. There's nothing wrong with the crankshaft sensor, camshaft sensor or anything with the motor itself. And, no... No codes.


    I didn't get a chance to check the fuel pressure again last night. I'll try tonight, but it's a mechanical gauge I plug into the fuel injector rail, I can't check it while driving. Last time, I power-braked it while Diablo watched the gauge. It was fine, I think around 50psi.

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    The gauge says around 3.something gallons per hour at WOT, it doesn't show the fuel flow rate besides that. I'll check through the options again when I drive home.

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    That 3 gal/hr is something the computer is calculating based on injector pulse-with and the flow rate of the injector, that doesn't really tell you much because its such a vague number. The thing you need to look for is a fuel trim number which may be listed as LTFT or STFT, a number negative means the computer is seeing a rich condition and pulling fuel (shorter pulse-with) and a positive number means its seeing a lean condition and adding fuel (longer pulse-with). This is probably one of the most informative things the computer allows you to see when it comes to a drivabilty problem. If you can find these values jot down what they are doing under a few different load conditions

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