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Discussion Starter · #1 ·
1998 Jeep TJ 4.0 six cylinders

1. Started with a miss fire code at 70 mph above 3k rpm, went into limp mode.
A. I replaced CPS and no more issues for a while.
B. It went into limp mode a week later, same conditions.
C. Then it ran fine for multiple outings.

2. I had tranny leak from multiple seals, pulled tranny and torque converter, fixed leaks and reinstalled.
A. No more leaks, Jeep shifted nice and idled good.

3. Went on a run in mount Charelston, no issues until i got at high elevation, i was in 4 high and noticed i was losing power, pedal to the floor it did not want to climb. So i dropped her in 4 lo. No better, no power at all. I stopped and saw smoke "i think exhaust" Jeep died in park under idle, it would bog down, shake until engine died. But it would fire right up. So i turned around and had no issues getting home.
A. I pulled my front skid plate and found an exhaust leak right past the intake manifold. So i headed to a shop to weld it shut. No shops open "sat" drove for 30 min with no issues, on way home she started bogging down, especially at a light, and ended up stalling 4 times.
B. Let her cool down and patched the hole with JB "temp fix to see if helps"
Started right up, but as soon as she reached temp she stalled. After warm she would stall every 30 sec after start.*
C. Started replacing parts
***** 1. New CPS
***** 2. New TPS
***** 3. New IAC
***** 4. New engine coolant temp
********** Sensor

4. She started right up, idled really good. Waited till warm and 10 min after and she didnt stall. I was happy, but that ended when i stepped on gas, she hesitated alot, and when i let off she would bog down to almost stall, also alot of pinging/popping from exhaust.
A. Replaced upstream 02 sensor, no help.
B. Replaced cap and rotor

5. She fired right up, idled good, stepped on gas and she bogged a lil, held gas down a little and let off, she died. Started right back up. Then i remembered i disconnected post cat 02, so with engine running i crawled under and went to plug it in, as soon as the plug touched it died. Went to start jeep and it wouldn't, just turned over but no start. Unplugged 02 and still no start. Looked at 02 connector, there is 4 prongs which were loose, and one was leaning over, may have touched each other when i went to plug it in while running?

So i ended up pissed off and taking a sawzall and cutting out my cat which i thought may be clogged or burnt up "cat was purple" anyway cat looks good inside to naked eye. And Jeep still wont start with it removed.

Now im sitting here in my messy ass garage frustrated admitting defeat.*
 

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Have you checked spark plugs? They will tell you how she's firing. Fuel too like others said. Your is a 98 so don't you have a coil and distributer? Do a obd2 scan and see if any more codes pop up
 

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Panthor, I am having similar issues as you so thought I would bring this thread back up instead of starting a new. Before I could always get it started again, but today trying to leave work it won't start no matter what. did you get yours fixed?
 

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Discussion Starter · #7 ·
Yes sir, ended up being the fuel pump. It would start and idle, even drive Sometimes. Fuel pump was weak, had enough output to maintain idle "most of the time" but under load it would die.
 

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Discussion Starter · #9 ·
No worries... Its a cake job really. Just dont go cheap on the pump "i bought a ebay Chinese crap one" lesson learned, a year later i went through getting stuck on a trail, blown fuel pump fuse. What a nightmare. Figured my pump was under a year old so gotta be good. Rewired entire pump harness from pdc to tank, new relays, any other item that was tied in was replaced or inspected or rewired. Finally 100 fuses later i dropped tank, for the 4th time that week and said f it, pull pump, its in 3 pieces, two wires completely broke and hanging, other two (power and ground) stripped bare. Kicker is it would still pump fuel like a champ, hence not checking it. It would just blow a fuse.

Ended up buying $236.00 OEM from Napa, they have a special going on "at least here" buy a bucket and get 20% off. So ended up costing 191.

Just an fyi 😉
 

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Thanks for the heads up. I ordered a cheap one off of Rock Auto last night because Napa was showing 269. I've read a few times that people had to replace the cheap pump again within 12 months so I'm going to get the more expensive unit from Napa. Thanks again!
 

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Well I replaced the cam position sensor with no change and then fuel pump yesterday. Started and ran well a few times yesterday. Now today it won't start again. I guess I'll try the throttle position sensor next. I was going to take it hunting next week but even if I get it running I'm not sure I'll have any faith it won't leave me stranded in middle of nowhere.

Thoughts?
 

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If u think it's the throttle position sensor just unplug it. It'll go into a bypass mode for the PCM and it'll still be drive able. I'd check the map/maf sensor. I had one come into the shop and that was the problem
 

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Discussion Starter · #15 ·
Most sensors aren't even read until jeep warms up, so i doubt its that. The only sensor i can see causing a no start may be the cps, pull your distributor cap, check for wear or burns on tabs, also check rotor.
 

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Discussion Starter · #16 ·
Hope you didn't buy your cps from AutoZone or O'Reilly, all sensors should be mopar. Pay the extra cash.
 

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Discussion Starter · #18 ·
Not sure about napa sensors, i dont know if they outsource from china. Might want to ask them, the computers parameters/variance in specs for these sensors are very minute. I went through returning 3 sensors before i went mopar, alot of threads about aftermarket sensors being bad out the box or going bad shortly after install.
 

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It just cranks but doesn't start. I'll try unplugging the tps.
I know you replaced your fuel pump but are you hearing the fuel pump run upon turning the key? I believe the fuel pump is going to run for about 2 seconds when you turn the key to run - this primes your fuel line. If you aren't hearing it pump then your fuel delivery is still questionable. Could be wiring, coyld be fuse, Maybe check your fuel pump relay in your fuse box. There are tons of videos on how to validate your relay. If your relay is going bad it may not be consistently supplying power during the startup sequence. Just a thought . . . Good luck.
 
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