# 96 jeep cherokee...4.0 running bad



## dchasteen (Jun 6, 2007)

Help

my 96 Jeep Cherokee with the 4.0 is having a running problem....it is back-firing, has a bad exhaust smell, and the tailpipe is black.

what is the problem?? I think it is a fuel related, but not sure...what do you think?

I have replaced...plugs, rotor cap, plug wires, water temp senor.

the jeep does have 170,000 miles but does not use oil

any help is appreciated....

dc


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## manic (Aug 2, 2005)

How about oxygen sensor, egr valve, throttle control sensor, maps,
Does it have a check engine light? If so pull some codes, that should 
narrow down the problem.


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## dchasteen (Jun 6, 2007)

I did get some codes, but know what they are:

P0118...1597...1683...0123...0113...0108...0505....0500

any help with these, much appreciated

or where I can go to sifer these codes

dc


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## Codeman0013 (May 8, 2007)

1597 Speed control switch always low 
1683 Speed control servo power control circuit problem. 
123 Throttle position sensor voltage high 
113 Intake air (charge) temperature sensor voltage high 108 MAP sensor voltage too high 
108 MAP sensor voltage too high 
500 Haven't heard from the speed sensor lately. 
505 The idle speed air control motor doesn't seem to be working correctly. 
118 Engine coolant temperature sensor voltage high 


Sounds to me like some major electrical problems in your car with your speedo and your engine coolant. I would take this to a repair shop asap or you may end up with a dead or overheated engine or worse an electrical fire in your engine.


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## manic (Aug 2, 2005)

What I would do first is this. Disconnect positive battery cable. Replace
oxygen sensor. If it hasnt been replaced in 170000 miles its due. Then 
reconnect battery cable. Start vehicle, see what codes you are getting
now. The thing is with all the sensors, is that if one thing is bad, it
will trip all other types of sensors that are not relevent to the actual
problem. Remember that every time you change a sensor you must 
disconnect the battery cable to clear the onboard computer. When you do
this it may take some time for the computer to settle in. When doing any
thing on the vehicle I recommend disconnecting the battery cable.


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## dchasteen (Jun 6, 2007)

these codes showing Amps Voltage High etc.....could the computer be going bad to cause all of these codes??

I have taken the Jeep in to a repair shop...this is how I got the codes...they charged me $480 for dianogistics and replace the water temp senor...and it still runs bad.

I don't want this to happen again...I am willing to pay for the problem to be taken care of and what was the cause.

Don't know what to do.

dc


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## Codeman0013 (May 8, 2007)

Are you in the us? If you are go to your local autozone and have them test it for you its free and they can tell you the code and what it means and most of the time they know what you need try that too but definately replace the oxygen sensor and after you reconnect the battery drive for a while to get the codes back go to autozone a few days later...


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## dchasteen (Jun 6, 2007)

is the oxygen senor by the calaytic converter someplace or is it under the hood somewhere??

do you know why the repair shop would not have replaced the oxygen senor, because they didn't and didn't recommend it??


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## Codeman0013 (May 8, 2007)

Depends like i said if you can go to autozone and let them test it and give us those codes as well. They can also show you where the sensor is on your car and usually you can change it in 10 mins and its not more hten like 30 bucks for the part.


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## manic (Aug 2, 2005)

oxygen sensor will be on the exhaust, maybe on the exhaust manifold,or
somewhere along the exhaust pipe, usually 2 or 3 wire, can be taken out
with a sparkplug wrench after you cut the wire, can be tough, but pretty 
simple. Depends on where its at.


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## dchasteen (Jun 6, 2007)

ok...exchanged the oxygen sensor...no difference in running..

but I have discovered a sensor on the intake manifold and when I took it out and started up the jeep it ran better and not back-firing....

it seems when the engine gets more air flow it runs better


well...really don't know what to do next....I discovered also another sensor back past the converter....is this another oxygen sensor?? could it be bad??

I am about to take my 45 out and shoot this.

dc


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## qldit (Mar 26, 2007)

Good Evening dchasteen, to elaborate on these learned gentlemen's suggestions and how this system operates may be worthwhile at this point.

The oxygen sensor is really the basis of this system, it normally consists of a simple coil winding of special metal, it is normally located in the exhaust manifold in such a position as to be able to sample the hot exhaust from all cylinders, presence of oxygen in the exhaust flow suggests insufficient fuel is being added, so the computer thus adds more signal time to the injectors. It does this very quickly and is a looped signal kind of automatic system. 

The amount of air and it's temperature going into the engine intake is monitored in the airbox, so any extra air that may be entering by poorly sealed intake ducting may upset the process.

If your description of overfuelling and "backfiring" refers to backfiring in the exhaust system then for some reason too much fuel is likely being admitted.

If your description of backfiring refers to the intake manifold it is completely different and could involve engine electrical timing or a valve problem.

Has the engine electrical timing been checked?
I suspect the distributor setting may need adjustment, I am assuming this is the spark timing base. (not a crankshaft speed sensor)
(Timing Light job)

It is common for fuel injectors to be erratic and not function properly, when these kinds of problems happen, I like to dose the fuel with "injector cleaner" and run some decent premium fuel, it helps in analysis and often clears odd problems.
If the fuel injectors do not follow computer commands and are "gummy" or "slow" or "dribbly" this kind of thing can happen. It may only be one injector with a stiction problem to create this kind of effect.
The injector cleaner usually allows a form of lubrication and gunk removal.
I don't suggest going further with injector analysis than this.

I don't know what the sensor would be in the rear exhaust path, but you are likely correct in suspecting it is another oxygen sensor. 

Cheers, qldit.


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## dchasteen (Jun 6, 2007)

thanks all for your help and suggestions

great day to all of you

dc


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## Blaine B. (Nov 26, 2005)

96 doesn't have an EGR.
Black tailpipe is normal.

www.naxja.org
www.jeepin.com
www.jeepsunlimited.com

Dedicated Jeep support forums if you didn't find a resolution here!


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## montie (Jul 6, 2007)

any one tell you to check your masairflow senser i would give it a try?


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