01 XJ, new injectors. Now it won't stay running. What am I missing here? - JeepForum.com
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post #1 of 5 Old 11-30-2019, 01:36 PM Thread Starter
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Join Date: Nov 2019
Location: Fredneck
Posts: 2
01 XJ, new injectors. Now it won't stay running. What am I missing here?

Hi everyone. Probably not the first person here to make their intro post also a help request, probably not the last.

I recently got a 2001 Cherokee XJ, my 4th. Before this I've had 90, 95, and 99. I'm not the biggest grease monkey, I mostly work in tech, but my dad and I work on stuff together.

This had a few things here and there wrong when I got it. Biggest of which being the rear diff. Recently replaced the kickdown cable since it was busted by previous owner. But now it's got both of us wanting to put our heads through a wall. I've been chasing down a misfire on cylinder 3 for the last month. First I did my plugs, then the ignition coil. Still kicked that code back every 3 weeks (I would reset the battery from time to time, see how long I can go without a misfire). It would stutter and sputter and then run fine but that CEL came on all the same. So I finally just said f-it and got a new set of 4 hole injectors. Could be that, got a good price, might as well do all 6. Immediately after is when s**t hit the fan.

Now it won't stay running. It runs a little jumpy at first, then smooth. Runs really well. But even if you let it alone for 5 minutes, it will calmly stop running. You can accelerate and it holds a steady RPM, but as soon as you let your foot off or try and slow down too suddenly, it will calmly stop running. We got a new IAC, CAM, MAP, and TPS. Still, same issues. I've reset the ECM/ ECU/ PCM/ Whatevertf, the battery method. Disconnect negative, touch to positive for 30 seconds. Turn key on, lights on, lights off, key off. I've even borrowed a buddies snap-on code reader and the only codes I found were the ones I was tripping by unplugging sensors to see what would fail it.

NOW I have P0122, low circuit to TPS

So, do I need to run to a scrap heap and dig out an old ECU? Or is there something I missed?

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post #2 of 5 Old 12-03-2019, 10:12 AM
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2001 XJ Cherokee 
Join Date: Aug 2014
Location: Franklin
Posts: 542
How is your fuel pressure at the rail? Have you tried the seafoam cleaning trick? What does your throttle body look like?

^These are the cheap things I would try out.
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post #3 of 5 Old 12-03-2019, 11:16 AM
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2001 XJ Cherokee 
Join Date: Oct 2019
Location: Lopez Island WA
Posts: 102
If you got "a good price" on a set of injectors from say, Ebay???.. I might suspect that you got what you paid for with knock-off Chinese injectors that are notorious for poor quality/performance.

If there is a local shop that has an injector tester [seem to be all over the place now] I'd take my old and new injectors in and have them test them for leaks/pressure/pattern/flow. You might find that the original Semeins are working fine and the new ones suck.

I have a 2001xj with 214000 miles that still runs great and gets combined [country road/freeway] average 19.1mpg, original injectors
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post #4 of 5 Old 12-03-2019, 11:59 AM
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2000 XJ Cherokee 
Join Date: Aug 2017
Posts: 1,528
IF my jeeps start,they run smooth and strong. i drive each at least weekly till hot.

they run strong,shift all gears,od and torq lock,all great...but i said IF.

if they need jumped its a new story.they WILL NOT idle.
i play with gas at 1500 rpm getting ware. let off gas and they drop dead. restart and repeat endlessly.
im convinced i should just start and die 10 or 20 time till ?? the computer relearns to idle.
i laughed when they said "weak" batt will cause this. my 1st xj,99 would start and idle

even when it needed a jump. not any more. my 00 xj WILL NOT run till "babied".
my 04 wj was fine till the batt went down the first time . now it needs

my daily driver,99 wj, new batt cranks a little weak but always starts and runs great.
it jumps the others all in a row.
so,what do we do??? i repeat, WHEN they start they run great,,,,but. btw i have never seen a spark plug or injector

btw the 99xj with a new batt,good clean connectors, is now dead. no lights,no crank,no nuttin

99wj,143,000 miles
00xj,177,000 miles
10hummer3,74,000 miles
98xj,130,000 miles
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post #5 of 5 Old 12-03-2019, 12:10 PM
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2000 XJ Cherokee 
Join Date: Apr 2002
Location: out in the garage - Minneapolis
Posts: 27,824
Perform in this order:
  • Solve the P0122.
  • Test injector circuit wire continuity, PCM to injector.
  • Test the fuel pressure.
  • Make sure all the tune-up parts are fresh.
  • Test the coil
  • Suspect the injectors are garbage.
  • Suspect valve or valve spring issues as the root cause of the misfire.

Only use genuine Jeep engine sensors and NTK O2 sensors. Most auto parts stores sell cheap crappy Chinese made parts, some that even come with a "Lifetime Warranty". These parts are poorly manufactured and/or made from inferior materials. They are often out of specification, or even failed, right out of the box. The ones that are not faulty many times will have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep engine sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.
Cheap parts are cheap for a reason.
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