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Thread: **Engine help**

  1. #1
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    Default **Engine help**

    hello all, my jeep seems to be running kinda sluggish.
    first off it has 65,000 miles on it,maintenence has been well kept.. about 2-3 months ago changed plugs,wires,dist cap,rotor,air filter,fuel filter...
    my problem:
    when i drive onto a highway or passing a vehicle it seems to be slow..
    i floor it and it downshifts ok engine kinda roars but doesnt really go anywhere.. looking at rpms and tachometer its definetly not slipping.. trans is good also.. no check engine light at all.. so im leaning towards maybe a sensor being faulty (tps,cts,o2 sensor) or maybe ignition coil not producing enough power??.. on city streets it drives and shifts fine..
    any thing i can look at or replace to help the sluggishness???
    ive owned jeeps before and they had no problem passing up semi's or slow running cars... so its not a jeep thang. thanks for ALL your time!!

  2. #2
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    Default Re: **Engine help**

    If you have never changed the O2 sensor, I would recommend starting there. Also, the cat might be plugged too. O2 sensors should be changed every 50K as part of a tune up
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
    Griffin radiator
    On board air
    Warn 9.5ti on custom bumper
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    30 gal gas tank
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  3. #3
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    Default Re: **Engine help**

    Quote Originally Posted by rm2406 View Post
    hello all, my jeep seems to be running kinda sluggish.
    first off it has 65,000 miles on it,maintenence has been well kept.. about 2-3 months ago changed plugs,wires,dist cap,rotor,air filter,fuel filter...
    my problem:
    when i drive onto a highway or passing a vehicle it seems to be slow..
    i floor it and it downshifts ok engine kinda roars but doesnt really go anywhere.. looking at rpms and tachometer its definetly not slipping.. trans is good also.. no check engine light at all.. so im leaning towards maybe a sensor being faulty (tps,cts,o2 sensor) or maybe ignition coil not producing enough power??.. on city streets it drives and shifts fine..
    any thing i can look at or replace to help the sluggishness???
    ive owned jeeps before and they had no problem passing up semi's or slow running cars... so its not a jeep thang. thanks for ALL your time!!
    Guess #1; Clogged exhaust system. Catalytic converter would be my guess. I've read you can IR temp scan them and they'll be really hot if that's the problem.

    Click image for larger version. 

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  4. #4
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    Default Re: **Engine help**

    if i check the cat for heat temp what temp should i be looking for?? can an o2 sensor be checked or should i just replace??

  5. #5
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    Default Re: **Engine help**

    Quote Originally Posted by rm2406 View Post
    if i check the cat for heat temp what temp should i be looking for?? can an o2 sensor be checked or should i just replace??
    One thing temperature measurements will tell you, however, is if the converter is working too hard. An infrared noncontact pyrometer or a temperature probe will tell you if the converter is running unusually or dangerously hot. If the converter outlet temperature is 200 or more degrees higher then the inlet temperature, it means the engine is running rich and there's a lot of CO in the exhaust that needs to be burned. A rich fuel mixture will often produce a "rotten egg" odor in the exhaust (the smell is hydrogen sulfide). Underlying problems may include an engine management system that is not going into closed loop (check the coolant and oxygen sensors, or for a thermostat stick in the open position), plugged PCV valve, or excessive fuel pressure (bad fuel regulator). High CO levels in the exhaust can also be caused by an inoperative air pump system.

    If the outlet temperature is a lot hotter (more than 500 degrees F) than the inlet temperature, it indicates unburned fuel in the exhaust. The most likely cause would be ignition misfire (fouled spark plug, shorted or open plug wire, cracked distributor cap, arcing rotor or weak coil), or a compression leak (burned exhaust valve). But other causes may include lean misfire (check for vacuum leaks, leaky EGR valve, low fuel pressure or dirty injectors). A single misfiring spark plug can cause an increase in HC emissions of 2,500 or more parts per million, which can push the converter's operating temperature well above its normal range.

    A common external clue of overheating to look for is a badly discolored or warped converter shell.


  6. #6
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    Default Re: **Engine help**

    O2 sensors wear out over time and cause the engine to run rich generally, which can lead to a clogged cat over time. We had a podcast on this a few weeks ago. But basically you should replace the O2 sensor every 50K. It is the most neglected tune up part there is. I second the advise on checking the cat for discoloration, and also the pipe and muffler behind it
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
    Griffin radiator
    On board air
    Warn 9.5ti on custom bumper
    7.5" RE front and bastard pack rear on custom long arms
    30 gal gas tank
    lockers
    And a bunch of other stuff

  7. #7
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    Default Re: **Engine help**

    thanks all, will do today after work..

  8. #8
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    Default Re: **Engine help**

    Quote Originally Posted by rm2406 View Post
    thanks all, will do today after work..
    Yep changing the O2 sensor is just a good idea. If it doesn't solve any problems hang on to the old one as a spare. Might hang on to it anyway. Be sure and label it though.

    Also I've used Bosche(sp?) and Chrysler. I haven't noticed a difference between the two. One is 60 the other is 120(I think).

  9. #9
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    Default Re: **Engine help**

    My first thought was the cat converter too. Had the cat partially clogged in my '98 XJ & had much the same symptoms.

  10. #10
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    Default Re: **Engine help**

    When I bought my jeep the cats had been removed so I don't have to worry about cats.

    Luckily there is no emissions here in South Carolina.

    Just had to say that I was almost banned off of another forum for saying I had no cats.
    Its my pride and joy, it's known as, the addiction 1999 4.0 4x4. It took years to find but only seconds to love, But most people never know the joy because, it's a jeep thing

  11. #11
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    Default Re: **Engine help**

    Quote Originally Posted by Andrew XJ View Post
    When I bought my jeep the cats had been removed so I don't have to worry about cats.

    Luckily there is no emissions here in South Carolina.

    Just had to say that I was almost banned off of another forum for saying I had no cats.
    And i could probably guess which one.

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