Sputtering / hesitating / stalling after lifter replacement (out of ideas and desperate for help)

JeepDawg25

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This might be a long one - I appreciate your patience in advance because I am mentally at rock bottom right now. 1995 Wrangler 2.5L manual with extremely rough/shuddering idle and no power on acceleration.

I have been dealing with a ticking lifter since buying this Jeep and got that god forsaken itch to finally do something about it. Ordered some Sealed Power lifters and Enginetech pushrods/rockers/pivots from RockAuto and it was surprisingly easy. Steps taken:
  1. Added ZDDP additive to the 10W-30 still in the crankcase (about 500 miles or so since last change). Aimed for 3000ppm for the break in since I kept the old cam.
  2. Applied assembly lube to all mating surfaces. Made sure to torque the rockers evenly at 21 ft/lb
  3. Turned the crank by hand a few rotations to make sure all the pushrods moved as expected
  4. Broke in the lifters for 15 minutes cycling between 1800-2500 RPMs.
The end result was a wonderfully quiet engine - after the break-in I sat for a few minutes listening to that lovely idle and the n shut it down for the night.

The next day, drove 2 miles down the road with everything normal. On the 2 miles trip back, I started noticing a hesitation/power loss around 2200 RPMs that did not exist on the trip out. Accelerating in that RPM range would cause it to hesitate with no power and almost sound/feel like a semi-truck engine braking. By the time I got home, any throttle over 1400 RPMs would cause the same hesitation. After sitting in the garage poking around the engine bay for 5 minutes or so, the idle got super choppy. At its worst, it would almost "pulse" 4 times a second or so, the entire engine block shaking and the entire Jeep shuddering. After doing this for about a minute, it stalled out.

Here are observations over the last week:
  • Starts right away but it immediately shudders at idle (I wouldn't dream of trying to drive it anywhere)
  • It inevitably stalls out eventually - sometimes after a minute, sometimes after 20.
  • I can give it throttle in neutral and it will sound normal up until 2k RPMs when it hesitates/misfires.
  • Sometimes it will idle roughly and then out of nowhere, smooth out and idle basically like normal. Almost like she is waking up from a dream or something. But minutes later it always returns to the rough idle.
  • Smells strongly of fuel and will spit black soot out the tailpipe.
  • Issues do not seem to clear up once operating temp is reached
  • After shutting her down, I will hear a single metallic sound from the muffler area after 5-10 seconds - think two pieces of sheet metal hitting together.
Here is the troubleshooting I have done:
  • Compression is good - ~145-150 in all 4 cylinders. Oil pressure good at ~55-60 (consistent with pressure reading pre-lifter replacement).
  • Fuel pressure has always been a little high (~45psi) and this number has stayed consistent during my troubleshooting. I suspect a pinched return and thus tried running the engine bypassing the return to the tank - no change.
  • All 4 plugs are getting spark (confirmed with inline tester)
  • Diligent throttle body cleaner spraying cannot identify any vacuum leaks
  • Replaced spark plugs/wires, IAC, TPS, and MAP sensors. Cleaned throttle body. Changed oil.
  • Confirmed consistent injector operation via stethoscope
  • Removing the valve cover and observing the rockers at idle shows consistent lift and good oil throw.
Based on my steps so far, I have done what I can to check spark, air, fuel, and compression...what the heck am I missing? My next thought is vacuum gauge to test for back pressure - maybe the exhaust is clogged (no catalytic converter on the vehicle as far as I can tell). Or perhaps a timing issue even though I didn't touch the distributor or timing chain - does turning the crank by hand affect timing in any way? Would an O2 sensor problem cause this much headache (even though it shouldn't even come into play until up to temp)?

I am struggling to tie the actual lifter replacement to all these issues. There is no ticking, oil throw/pressure is good, and rockers appear to be getting consistent lift height across all cylinders. No rockers are misaligned on the springs, pushrods still appear straight, and there is no play in the valvetrain at all.

I know this is a beast of a post but I would sincerely appreciate any help - I have spent so much time troubleshooting on my own that I am seriously contemplating listing for basically scrap price and being done with it.
 
Possibly a bad coil. My 4.0 got to the point it was backfiring and misfiring violently with a bad coil.

Have you checked the fuel pressure while revving the engine? But if you have soot and gas smell, it appears you have plenty of fuel.
 
Also, you can unplug the O2 and see if that helps. The PCM will fall back to a preprogrammed mixture.
That is a good idea, I will try tomorrow. At startup in closed loop, would the mixture be affected by that sensor though?

Also thanks for the idea on the coil. I will Google as well, but any tips on testing there?
 
Startup is in open loop, not using O2s. Just coolant temp, air temp and MAP sensors.

Closed loop is at operating temp and uses O2s.

No real good way to test an intermittent coil that I know of.
 
Thanks - will test tomorrow and maybe looks at those other sensors too.

Although at this point, I haven’t gotten a single code thrown. I would expect something to flash if one of those sensors was so horribly off that the engine can barely hold idle.
 
Since this all started shortly after lifter replacement, could the engine management computer need to be reset? I am not sure about your Jeep computer but I was told by my GMC dealership years ago to go this on my truck with an issue I was having. On the GMC I had to disconnect the battery for awhile I can’t remember how long, and it was supposed to clear the memory and start over.
 
Thanks for the reply - I read something similar and have had the battery disconnected a few times overnight to be safe…it doesn’t seem to have an effect on the issues.
 
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Resolved! I appreciate all the suggestions but the culprit was one of the new lifters getting eaten up by the cam and (probably) causing a valve issue. Last night I finally bit the bullet and dug back into the valvetrain and removed all the new components (should have been my first troubleshooting step, honestly) and the third lifter from the front - intake I believe - was clearly worn way beyond what should be expected after ~4 miles of driving and ~30 minutes of post-break-in engine time.

Spent a sleepless night trying to decide whether or not to go ahead with a full camshaft replacement, but visual inspection of the cam lobe didn't show much wear. I crossed my fingers and hoped that the old cam delivered the damage to the lifter and didn't get much back in return - after dropping in all the old components (including the original ticking lifter that caused me to do all this in the first place), everything appears to be running smoothly after another break-in and about 20 miles of driving. I doubled the break in and did 25 minutes of 2500-3000 RPM, changed oil and filter, then did another 20 minutes...maybe overkill but if I underestimated the importance of break-in before I didn't want to make the same mistake twice.

I know I am not out of the woods yet, and there could be cam damage that just hasn't revealed itself, but after reinstallation I didn't get a single instance of misfire/stumble/sputter going through all the gears and up to ~55mph. I was cautious not to let it idle for more than a few seconds, trying to keep the tach at 1800+ and treating it almost like an extended break in period. I will change the oil and filter after another 100 miles or so and check for fragments. And the real kicker - my old lifters aren't even ticking anymore. So as of now, the end result is a VERY smooth idle and acceleration after troubleshooting the throttle body/IAC/AIT sensors, no more lifter ticking, and a much wiser Jeep owner (who can do a full lifter replacement in less than two hours from start to finish!). If I get any further indication of a cam lobe/lifter problem, I will go ahead with a full camshaft/lifter replacement kit and will update here in case anyone in a similar situation has followed along.

Thanks all for the troubleshooting advice, I am sure it will come in handy next time something breaks!
 
Good job my friend. I also am going through some similar situations with a newly rebuilt 2.5 install. Ran great during break in time. Drove to a buddy's house and starting it back up to leave. It went down hill right now. And like you, I was hesitant to check the obvious because I did not want to believe that something was wrong internally. After checking everything else first, I pulled the valve cover to find my problem in no 3 cylinder. Had a bent pushrod. (So far) I am going to pull the head right now to see what the extent of the damage will be and hopefully can use some of my old stuff of old motor to drive this thing today. I was just in denial and posted here with hopes of someone telling me it was going to be something easy but after facing up to it and taking a deeper look, the obvious was right there waiting . I don't know what I was trying to get out of it because in the back of my mind I already now the motor went wrong somewhere during break in or whatever and I guess I was trying to keep from being embarrassed and was like, "see no evil, hear no evil...) but the blinders had to come off because out of options and still had a non running heap of jeep outside on the patio. I love my jeep and I know they have more then their fair share of issues but I have discovered that it's not just a vehicle, it's a way of life. Everything it stands for and the people who will wave to you as you pass them by in their jeep, and the freedom to go where you want to when you want to and the jeep community is just something that you get when your a jeep owner. Where I am at there is a few off road recovery groups who will help anyone anytime who needs it and are active in the community and do toy drives for kids and cool stuff. Not to long ago, at the request of a single mother. In the area there was a little bits birthday and covid was running through here in a bad way but the group still helped the little birthday boy have a good memory. The group did a drive by in all their rigs and made the little guys day. Just an example of the feeling I have when I say it's not just a vehicle, it's a way of life. By the way, I am proud to say I am a member of their group.