Jeep tj wont run and im fed up. - JeepForum.com
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post #1 of 37 Old 06-18-2019, 08:28 PM Thread Starter
Tyseals81
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Jeep tj wont run and im fed up.

Ok i am a new jeep owner, about 2 months. I purchased a 97 jeep tj with a 4.0L and an auto. When i purchased it there was an issue where when you started the engine it would miss and spit and sputter for just a min then would be fine all day until you shut it off and restarted. Fast forward trying to fix it I replaced the idle air sensor, crank sensor, several cans of seafoam, and cleaned the intake, to no avail. So then i replaced the distributor since the cam sensor is built into it. Once replacing it the jeep didnt want to start or run so i assumed it was a tooth off so i took it out and in process it broke so i put the old one back in. Now the jeep barely starts and once started it cant be reved up because it starts backfiring and missing a running horrible. But it idles fine. Timing is correct, plug wires are correct. So i replaced the cap rotor coil still no change. Took it to a shop and he couldnt find the issue. Combined we thought it had to be the pcm so yesterday i put a new one in it and what do you know still wont run. I took the valve cover off to check that there wasnt lifters stuck there wasnt. Has 48 psi fuel pressure and it shows no codes at all. I need help im about done with this piece of junk.

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post #2 of 37 Old 06-18-2019, 10:18 PM
mukluk
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Quote:
it would miss and spit and sputter for just a min then would be fine all day until you shut it off and restarted
I'd say about a 90% chance this is due to a bad upstream o2 sensor, specifically the heater portion of the sensor. Early TJ's commonly will not register a fault code for bad o2 sensors.

With the running problems getting notably worse after the distributor was swapped out, I would recommend triple checking the install position and whether the cam sensor is properly oriented. Is the Jeep showing any stored codes when you check with a scanner?
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post #3 of 37 Old 06-19-2019, 06:06 AM
Trootncsse
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I second rechecking the cam sensor. The symptoms you describe first are exactly what I had back last year. Cam sensor had one bolt in it and it was loose.

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post #4 of 37 Old 06-19-2019, 07:04 AM
jtec
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How did you check for codes - I am hoping you have a scanner.

Fuel pressure - try this attach gauge, turn key to on observe pressure record high reading - then leave key on observe pressure drop record PSI in 5minutes.

you removed the dist then replaced with a NEW unit?
did you have engine at #1 TDC compression - checking your install.
Like colleague Mukluk this is a place to focus.

Keep your original PCM ! do not return yet.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #5 of 37 Old 06-19-2019, 09:46 AM
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Also the Jeeps are sensitive on the sensors that are used. If you do replace the upper O2 sensor, use only NGK/NTK brand..
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post #6 of 37 Old 06-19-2019, 11:32 AM Thread Starter
Tyseals81
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The old distributor has been put back in the jeep since the new one the hold down bolt tab broke. It ran ok with the old distributor before i changed it now it doesnt. I took it to a shop and he checked timing it is all correct and he put a scanner on it and there are no new or stored codes and he ran a diagnostic test with his computer and it showed all was good and no issues but it wont run.
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post #7 of 37 Old 06-19-2019, 12:01 PM
mukluk
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Please verify if the Jeep will start or not -- you've stated it will barely start and idle but not rev then contradicted that and said it won't run.

Have you checked if you're getting spark at all the plugs? How do the plugs look? Did the cam sensor harness possibly get damaged during the distributor swap?

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post #8 of 37 Old 06-19-2019, 12:10 PM
jtec
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I am a little skeptical that the scanner was no help. You are not clearing codes or removing battery?

SO lets start over - 1997 jeep wrangler automatic,
It Will start idles ok?

As there are no codes I would look at fuel - with a gauge - turn key to on record and post hi fuel pressure next leaving key on observe fuel pressure drop post reading at 5min.

install original PCM.
Is the airbag light on?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #9 of 37 Old 06-19-2019, 09:52 PM
Deltacottonboy
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Upstream 02 sensor (your 4.0 has 2). The o2 sensor will not throw codes but will make your jeep run like absolute garbage. Backfires, hesitation while accelerating..... took me some time to track down my issue identical to yours. My 2.5 only has 1 upstream 02 sensor. Per my jeep man's recommendation, I disconnected the negative battery while I replace the 02 sensor (this was supposed to delete "learned data"). Reconnected everything and she runs like a sewing machine.

Before you do anything else, buy NTK upstream sensors and give it a try.
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post #10 of 37 Old 06-20-2019, 09:48 AM
BM3
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Quote:
Originally Posted by Deltacottonboy View Post
Upstream 02 sensor (your 4.0 has 2). The o2 sensor will not throw codes but will make your jeep run like absolute garbage. Backfires, hesitation while accelerating..... took me some time to track down my issue identical to yours. My 2.5 only has 1 upstream 02 sensor. Per my jeep man's recommendation, I disconnected the negative battery while I replace the 02 sensor (this was supposed to delete "learned data"). Reconnected everything and she runs like a sewing machine.

Before you do anything else, buy NTK upstream sensors and give it a try.
No IIRC a 97 has 1 upstream and 1 downstream O2 sensor. TJs with the mini cats will have 2 upsteam sensors, not sure on the year they changed to that configuration
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post #11 of 37 Old 06-20-2019, 10:51 AM
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Understood. I knew the 97 2.5 tj had single o2 sensors but didn't know the 4.0 did as well. Thanks for informing me.


Quote:
Originally Posted by BM3 View Post
Quote:
Originally Posted by Deltacottonboy View Post
Upstream 02 sensor (your 4.0 has 2). The o2 sensor will not throw codes but will make your jeep run like absolute garbage. Backfires, hesitation while accelerating..... took me some time to track down my issue identical to yours. My 2.5 only has 1 upstream 02 sensor. Per my jeep man's recommendation, I disconnected the negative battery while I replace the 02 sensor (this was supposed to delete "learned data"). Reconnected everything and she runs like a sewing machine.

Before you do anything else, buy NTK upstream sensors and give it a try.
No IIRC a 97 has 1 upstream and 1 downstream O2 sensor. TJs with the mini cats will have 2 upsteam sensors, not sure on the year they changed to that configuration
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post #12 of 37 Old 06-20-2019, 05:47 PM Thread Starter
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Sorry for the confusion, the jeep does start and idle, just hard to start and cant rev up. I say wont run meaning its undrivable in this condition. The plugs are all new dnt remember what brand. The only code is has thrown was random misfire on all cylinders. I checked the fuel pressure with it running and it had a constant 48psi. I am wondering about the harness connecting to the distributor. As of right now i have made an appointment at the local jeep dealership for them to look at it so we will see what happens. But im still gonna keep looking till the appointment.
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post #13 of 37 Old 06-20-2019, 05:49 PM Thread Starter
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Correct i have not cleared any codes and the battery was not unkooked since ive owned the jeep
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post #14 of 37 Old 06-20-2019, 06:03 PM
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Bad or clogged cat...?

2003 X, 5 speed, FT/RR bumpers by Eddie Reighard. JKS 1" body lift, JKS disco's, 2 1/2" Rough Country lift, 8k Warn, w/class 3 receiver FT & RR hitch. GA 8 rims riding 33's- GY Kevlar.
SOLD- 1985 CJ7 soft top , fiberglass body, 5" total lift258-6- Howell TBI, Full Roll cage.
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post #15 of 37 Old 06-20-2019, 06:41 PM
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I dispute that the O2 sensor is the culprit... A vehicle starts in open loop. The PCM could care less what the O2 is saying. Open loop is a predetermined program that should start and run an engine cold. Period. Depending on application is where the O2 starts to figure in. It may still be a problem, dont get me wrong... It does not look at it for start up though...

You said you changed the spark plugs. New but don't remember what brand..... I have fixed a zillion vehicles by going back to OEM plugs. A zillion! I have NEVER found a vehicle that runs correctly with Bosch plugs. Chevys dont like champions, Asians dont generally like things that dont say Denso or NGK. JS. Spark plug crossover charts are a joke! On and on.

If you cannot fix it with a hammer then it has to be an electrical problem.
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