4.0 having issues

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boogie94xj

NAXJA Forum User

Location

new tripoli pa

• Jul 11, 2003

• #1

New heep ran like crap when I got it. Changed plugs wires cap and rotor along with fresh gas. Major improvement. Still had a stumble between 2200 and 2500 prm while driving. Felt like the TPS was going. Checked and its bad. Changed it but still have the stumble. This thing is starting to make my brain hurt...please help!?!

 

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satan

NAXJA Forum User

Location

Lakewood, CO USA

• Jul 11, 2003

• #2

If you had issues with the fuel - suspect the filter and injectors as well (replace the filter and run some good quality cleaner for a tank or two)

 

M

martin

NAXJA Forum User

Location

Huntsville, AL

• Jul 11, 2003

• #3

May need to have the throttle body cleaned, may have a build up.

 

GSequoia

Everyone says I'm a jerk.

NAXJA Member

Location

Torrance, CA

• Jul 11, 2003

• #4

Yeah..what Martin said....

I'd take off the throttle body (get new gaskets first ) and give it a very throrugh cleaning. Take it apart and do it real good. Also as Satan suggested the injectors may be a bit clogged. Just chnage out the filter and run cleaner though for a bit as well.

Have fun with it!

Wait...

Do you smell gas any? It's possible your injector O-Rings are leaking (or even that the injector itself leaks, it's known to happen), check into that as well.

Sequoia

 

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boogie94xj

NAXJA Forum User

Location

new tripoli pa

• Jul 12, 2003

• #5

I replaced the filter when I did the other stuff...sorry I forgot to mention it. I hosed the TB pretty good with cleaner as suggested and she still acts stupid. Thanks for the assistance. I might just have to bite the bullet and pay the $60 diagnostic charge at the stealership.

 

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boogie94xj

NAXJA Forum User

Location

new tripoli pa

• Jul 12, 2003

• #6

The part that really has me grumpy is that if I back off the throttle or mash it to the floor there is no more stumble/backfire/loss of power. It almost feels like I am getting an incomplete burn/not firing temporarily.

 

RichP

NAXJA Forum User

Location

Effort, Pa

• Jul 12, 2003

• #7

Did you get the carb/fI cleaner inside either of the sensors in the throttle body throat ??? They are plastic and the cleaners are not plastic friendly.

 

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MACH90XJ

NAXJA Forum User

Location

Oregon

• Jul 12, 2003

• #8

My vote is clogged injectors.Simple test ,unplug one at a time,note any engine speed difference.If no engine speed difference theres your problem injector.If you have had a bad blow by problem in past that was not fixed,like mine was when I bought mine, you might be gummed up all the way through the intake system including injector tips.

 

J

jimmy forbes

NAXJA Forum User

Location

south carolina coast

• Jul 12, 2003

• #9

try a map sensor and a O2 sensor on mine 1 went then they all did
jimmy

 

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boogie94xj

NAXJA Forum User

Location

new tripoli pa

• Jul 12, 2003

• #10

The entire pcv system was taken off and a mr gasket filter/valve was put on it. I was thinking of replacing that with stock parts. I'll give the injectors a test and let you know what I come up with.

 

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DPC

NAXJA Forum User

Location

Washington

• Jul 13, 2003

• #11

I have the same issue with my 90'(cuts out about 2000/2300rpm with a slight backfire). I was getting huge amounts of oil blow by through the front "fresh air hose" into the airbox. Found that much of my major oil leak is in the air box!?!. I had all stock fittings/hoses with good vacuum to the CCV hose(the rear one) and still got blowby. Today I plugged the air box and added a KnN style breather on the fresh air hose. Thus no more blow by but still a stumble. I think it might be the injectors but also may be a sensor issue (oil fouled o2?). Whomever figures it out first will have to share the info.

 

ACE

NAXJA Forum User

Location

N. Utah

• Jul 13, 2003

• #12

If it's older and has any amount of miles on it, I'd vote for the map sensor or O2 sensor, more likely the O2.

 

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boogie94xj

NAXJA Forum User

Location

new tripoli pa

• Jul 14, 2003

• #13

Well I had some luck with mine. Did a pulse/pressure drop test on all my injectors and they were OK. While I was poking around I found a tiny vacuum port that had been plugged became slightly unplugged. Put a new cap on it. Also replaced the O2 which looked pretty rough. Took it out for a test spin and the thing ran terrible. I mean I could barely get it around the block. Gave up on it for the day. When my BP finally came down I took it out again and the heep ran like a charm with no troubles so far. Of course i probably just ruined it for myself by sharing but that's life as a jeeper. I'm thinking after all the replacing of stuff I should have disconnected the battery and reset the computer.