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  1. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Are they? Good, I wasn't sure. So that leads me back to thinking the miss is electronic. The only thing so far that's made any impact was replacing the ignition coil. I didn't hear the miss after it was replaced, my mechanic didn't hear the miss, but it came back a few days later. It's...
  2. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    New compression test, in order cylinders 1 - 6: 142 155 152 172 162 158
  3. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    I'm considering pulling the head and taking it to a machine shop. I'm still driving it, it's behaving well otherwise, but I want to fix this before it leads to other problems. Hmmm. I'll look into those, I'm really just out of ideas other than maybe a tiny amount of coolant is leaking through...
  4. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Bummer. Hoping for an easy fix. I'm thinking there's got to be an electrical issue somewhere. At this point I'm tempted to get a oscilloscope and check every circuit in the thing. I may go have the compression checked again, maybe the first mechanic botched it. Thank you! Have some tests...
  5. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Sorry, ended up in the hospital, took some of the steam out of my repairs. I replaced the throttle body again, this time replacing the TPS as well, now it's running normally other than the miss. I had my fuel injectors cleaned on one of those injector rigs. They all sprayed well, just a...
  6. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    I changed the TB entirely a few days ago, unfortunately no change to the miss. I swapped the IAC with an off brand, no change so I swapped it back. When I cleaned the TB I followed a post of Jerry Bransford; ran the Jeep and sprayed directly in the TB, let it get close to stalling a few...
  7. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Wasn't the distributor. Moving on to fuel injectors next.
  8. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Exactly. But even sealing it all up, confirmed with the smoke test, the Jeep barely ran. Put the old one back on, it's back to where it was.
  9. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    It really makes no sense that it would make a difference. I even noticed on the new TB that the IAC sat a little loose, so I replaced the o-ring and no change. Stopped and started the Jeep multiple times and it ran terribly. Then as soon as I put the old one back in it started to run more...
  10. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Reinstalled the old TB, everything went back to the way it was. At least I'm no worse off. But it's strange that the miss went away for a short time.
  11. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Replaced the throttle body today, confirmed with a smoke tester that there were no leaks. When I started it, it ran great, no miss. Then slowly the miss came back, then the idle got rough, then it started trying to die, and when I ran my scanner I have both upstream and downstream O2 high...
  12. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Guesswork based on experience, but no testing on-site, so all with a grain of salt. Ordered an automotive smoke machine. I hooked my vacuum tester to the intake the other day and the vacuum leak was back, and I'm done chasing it with starter fluid. I found the throttle body leak is still...
  13. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Okay, took it to a guy who rebuilds 4.0s, as well as race cars and vintage cars. He listened, said it doesn't sound like it's from the engine failing in any way, he said it sounds electrical or ignition. He suggested replacing the distributor, which is something I probably need to do anyways...
  14. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    You know the sound when you let off the gas while in gear? The popping from the exhaust? It's similar to that, just much milder. That's the closest sound to what my engine is making.
  15. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    The stethoscope says all injectors are clicking, and at the same rate. Tried with the probe against pretty much every surface of that engine that I could reach and I can't hear the miss from anywhere, but it's there. Discovered that one of the ears that the distro cap bolts to on the...
  16. M

    Distributor Replacement

    Hello! I'm looking to replace my distributor. I notice you can't find Mopar on RockAuto or Amazon, it looks like the best ones they have listed are Cardone. New https://www.rockauto.com/en/moreinfo.php?pk=12964005&cc=1431777&pt=7108&jsn=603 Reman...
  17. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Did that. Ran the whole can, let the Jeep sit for 20 minutes, drove it hard as heck for about 30 minutes. No smoke. Or it was so minor I didn't notice it.
  18. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Ran the Seafoam through the intake. No smoke out the back, apparently things were already pretty clean. If it weren't for that misfire it's running like a top. Tried a timing light just to see if there were spark issues, everything looks fine. Forgot to do the stethoscope; if it isn't...
  19. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Okay, I've got a mechanic's stethoscope, so I'll try that tomorrow. Been raining all week 🙄 I take it you mean Seafoam the crank case? I ran some through the gas recently, but never tried in the oil. With Seafoam you just run it for a few hundred miles and then change the oil, right?
  20. M

    RPM dips/engine stalls at idle (intermittent), 99 4.0

    Oh, I was just thinking out loud mostly. No one has smoked the intake other than me, and I've only viewed it from the top, I'll need to smoke it and crawl under just to check. That's part of my problem, most of the time the "miss" is light, especially after fixing the TB vacuum leak, and I...
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