I have a random misfire with no codes, 1999 TJ 4.0 manual. You can hear it, the vehicle shakes a little when it happens, but I don't have, and have never had, a misfire code.
I've changed the crank sensor, TPS, chased down a vacuum leak and repaired it. Throttle body gasket changed. We tried pulling each injector harness with the engine running but there was no difference in performance degradation and the misfire continued. I tested fuel pressure a few weeks ago, and while I can't remember the values off the top of my head I had looked up what it was supposed to be and it was dead-on. Plugs are iridiums, installed about two years ago. Cap and wires as well.
I was driving back from out of town a week ago, it was bucking at high speeds, running a high idle (1200 RPM), though at idle it would sometimes try to stall. I was stuck on a long road trip and had to drive it about three hours that way. Replacing the CPS seems to have fixed the bucking issues, the TPS fixed the high idle.
I've searched a bunch of threads, but most involve a code, or have worse symptoms than mine. You can hear/feel it, but the engine runs and gets me where I'm going.
I'm at a bit of a loss here. Would anyone recommendation a next step? Is it safe at all to drive it like this?
The way I locate random misfires is to identify when it happens. IE 3rd gear, 35 mph, 20% throttle slight uphill etc . Try to recreate the misfire and when it happens hold it in the misfire even if you have to use the brake to keep the load on it. If the check engine light comes on, check the codes to see if it identifies a cylinder. This narrows it down to one cylinder.
4.0 timing chain tensioner is a curved black plastic spacer.
I don't think you'd have any issues turning the engine backwards.
Another trick is to start it up in the dark and look for any shorts on the plug wires, you'll see faint blue sparks. I know you said the wires were only 2 years old but this is an easy and free way to check for leaks.
Here's a fun thing: my number one and number two fuel injector harnesses were switched. However, switching them back to the correct orientation just made the misfire worse. Not a harder misfire, but much more rapid.
Makes me wonder about the entire injector harness.
I'd be continuity checking everything back to the ECU plugs.
Noid lights might help.
Try swapping the 1 and 2 injectors with the wiring correct.
How did the 1 and 2 plugs look?
Question: I'm looking up NOID lights, they are all marked with different vehicle makes, but none of them are Jeep or Chrysler. Are there any others that can be used?
Some look darker than the others...or that's just shadows...wondering if we could equate the tanlooking ones to cylinders and that black one to the one not firing at the right time.
The TJ uses siemens injectors... pretty common plug...I would imagine most kits have the connector.
Since the PO replaced your injectors...do they have a Mopar stamp?