Stalls while driving

So the long version. Motor is stock. No mods. It ran perfectly for four years, then occasionally would just shut off in third and fourth gear. Pull over and it would crank back up. Then one day it started stalling a lot in third and fourth only. Was also back firing from tail pipe. Blew out the back of the muffler. Decided to do a tune up and replace muffler. Plugs, distributor cap, fuel pump. Cracked up. Test drive fifteen to twenty minutes in it shuts off and wont start. Tinkered for a bit, couldn't get it to start and gave up took it to a "mechanic". They were going to check the timing chain, so I told them to replace it while your are in there. They told me it jumped a tooth. I never saw it. They called a week later and said they cant get it to run, they give up, come get it, hence I call they "mechanics." I tow it home, open the choke and it cranks right up! Runs great, then rpm's drop and sounds weird, I will upload a video of sound. I decided to replace coil. Then it wouldn't start. Got an ignition module. Still no start. Then found that the starter solenoid was not getting power. Got power to the solenoid and it cranked right up. Sounds great, running great. Then temperature hits 170 ( I watched the gauge) and the revs drop and tone changes at exhaust. Blipping the throttle sounds terrible, but continuous throttle behaves okay.

Temperature gauge is a mechanical that is connected to the engine.

I am told the chain was replaced, I have not opened it to check.

I got it figured out. I got a timing light and the timing was at Zero to 5 degrees advance. Adjusted to 4-5 degrees retarded and runs fine. Drove around about 30 minutes with no problems.

Thanks Medic!
I did unhook the vacuum line when setting the timing.

I will adjust it to 13 sometime this week and let you know.

As far as the distributor operation, I did check that the timing line moved when the motor was accelerated. How much should is change?

I have the carburetor pretty well dialed in. I have been adjusting motorcycle carburetors for years.

Okay, back again. Have the timing and carburetor all dialed in as recommended by CJ Medevac. Drove around town a few times no problems. Today was out on a longer stretch and running 50ish mph in fourth gear when it looses power. More accelerator does not do anything. Pull into a road, back into second gear and fine. Back out on highway, does it again, followed by a tailpipe backfire (small). Heading home motor completely shuts off in third gear, pull over, cranks right back up. This only happens at "higher" speeds in third and fourth gear.

This was happening before and I did a tune-up, plugs, dist cap, fuel pump, filter.

Any ideas?

Thanks Tony

Thanks.
I will pull the new ICM off and get it tested.
When it loses power I can floor it and nothing changes. Would think the mechanical fuel pump would still be pumping.
Left off of my"tune up list" that I replaced the coil and the ICM.

So new development/finding. Took test drive before pulling new ICM out. Mile or so from home, go to accelerate in third gear, no acceleration. Give it more throttle, no revs. Putt up to stop sign, first and second gear good, third, little sputter, shuts off, little backfire. Pull over cranks back up. Did this about four times going back home. Luckily coming down my street it shuts off but I had enough momentum to roll into the garage. Popped top of carburetor. Bowl is dry. Messed around with it. Seems to have a strong flow when the float is pushed down. So now seems to look like a fuel issue.

Was not bump related.

What is this metal box by the solenoid? Can't find it in my manual.

I know there have been no new post for a while, but did you ever figure anything out? I am having very similar problems.

I am having very similar issues. 1978 CJ7 232. Idles fine and runs fairly well until about 10-15 minutes of running time. Once it gets to temperature, about 190 according to gauge, it will still idle fine, accelerates through 1st gear fine, go into top end of 2nd then begins wanting to die. It happens very much so in 3rd gear. Motor begins to die, accelerating further does not help, let off accelerator and it may come back to life or may not. Usually, it begins by bucking pretty bad and have to let off accelerator. Typically have to let the motor go back to an idle speed, "catch up" and downshift to 2nd or 1st gear to continue running with little acceleration pressed. Typically, it will idle forever sitting at the house. If I fast idle say around 2000-2500 rpms it will run for several seconds, then begins to shut off.

Purchased the vehicle in 11/2021. Had water in the fuel when purchased and was not running. Pumped the water and old fuel out of the tank. Have since replaced carburetor (National Carburetor ND1291-NEW AMC and Jeep, 1975-1977, 232"-258", Carter-YF which is what was on it before I purchased and it has the electric choke which is hooked up), fuel filters 1 inline before pump and 1 factory style before carb both replaced 2 times, mechanical fuel pump and upgraded the ignition to HEI ignition. Thinking either the tank still has trash, and the pickup is causing the issue or it's a carb issue. Prefer not to drop tank until last resort. I thought of trying to run the motor off a separate fuel line to a separate tank to try to isolate first. Ran across these posts and thought would ask for advice first. I would like to confirm the vacuum lines are running properly too.

Timing is set at about 12-13.
Distributor vacuum runs to the vacuum port at top of carb underneath air cleaner.
Tried adjusting the mechanical vacuum advance in both directions which made the symptoms worse. Have the mechanical vacuum setting back to the factory setting.
PVC valve is in the front port of valve cover and runs to the carburetor port near automatic choke.
The rear port of valve cover has an oil breather cap.
Second vacuum port on carb at the base is capped.
Factory air cleaner removed and replaced with a small aftermarket air cleaner.
Smog / emissions removed. EGR / CTO vacuum ports are capped.

Hesitate to open the carb and begin making adjustments as I am not very familiar with carbs. I have the rpms set around 650-700rpms, have adjusted the idle and the fuel mixture as best as possible. See pictures for additional insight.

First, thank you so much for such a quick response. Before I start making changes I will add a few more details, add two more pictures and ask a few more questions.

The manifold vacuum source you want me to move the PVC valve vacuum line to is the CTO I think. See pics to confirm. (If it helps below, I will list how the EGR, CTO and Charcoal canister are currently set up by prior owners.) The brake booster is currently connected to this CTO line.

Question 1 - If I connect the PVC line to the CTO metal tube, what do I connect the brake booster vacuum line to?

Question 2 - do I cap off the choke heater port on the carb once I move the PVC line off of it? I think that is what you are referring to in your picture.

Question 3 - one of the prior owners removed all the smog control stuff. The metal tubes coming out of the manifold are simply crimped over. Is this a concern for what I am dealing with? Are these the potential open ports you mentioned above?

EGR Valve - Capped

Coolant Temp Override Switch
CTO Valve Small Port 1 - Capped
CTO Valve Small Port 2 - Capped
CTO Valve Larger Diameter Steel Line Port 3 - Currently connected to the Brake booster

Charcoal Canister - assuming it's only function now is for the fuel tank vent line port 3
Port 1 - Far Left front of motor port - Open
Port 2 - working towards firewall - connected to the windshield washer tank lid (no joke)
Port 3 - Line runs towards fuel tank
Port 4 - closest to firewall Open

Question 4 - Once you confirm the above, I will start making the changes and recheck timing. When I remove the vacuum line from the distributor to check timing, do I cap the port on the distributor and plug the vacuum line going to the carburetor?

Making progress. I don't think I have a port on the carb that will work for the brake booster. I have the vacuum port at the base of the carb that the distributor vacuum is hooked to currently. I have a port at the top of the carb which I think is the fuel bowl vent but is currently capped off. It is nowhere near large enough for the brake booster vacuum line.

The last available port would be the choke heater port. What should I do with this port? Cap it?

Back to the brake booster. I will add a T to the PVC line going to the CTO port and connect the brake booster vacuum to the T.

Regarding the charcoal canister, I just want to confirm it can be removed and just add the fuel filter vent in your picture to replace.