Running poorly/misfiring, code 33

[JeepsAndGuns]

Life and lots of crappy weather have been giving me fits.
It seems like it has been raining every weekend, then we had that big cold snap.
Then when I had a sunny weekend, I had so much other stuff going on, the jeep had to take the back burner.

I did have a little time a couple weeks ago to start it and let it run. It had been setting since my last post.
It started up ok, but I could hear the random missfire thing it does (sounds like it is not running on all cylinders, but the miss can not be traced to any specific cylinder).
I just let it set there and idle for 10-15 min while I was starting up a bunch of other equipment to let them run (lawn mower, JD gator, chain saws, weed eaters, leaf blowers, etc...)
After running all the other equipment for a bit and putting them all back up, I decide to drive the jeep.
It ran perfectly. At some point, it decided to clear back up. It ran like nothing was ever wrong.

However I know it is still not right, it is just intermittent. I wiggle wires and the harness everywhere I could and it just ran normally.

Rain dang near every weekend since has prevented any further work. And now, my actual job has started picking up and I have working 7-5 during the week, and 7-12 on saturday.

However after work today, it was sunny and somewhat bearable temperature (mid to high 50's).
I brought home a headlight wiring harness from a lawn mower. It has two single filament light bulbs the same as what is used in a lot of older vehicles for brand or signal lights (1156 bulbs).

I still think the issue is ignition related. So I disconnect the ecu, disconnect the distributor connector, then using a paper clip in the ecu connector, I use a jumper wire and ground each of the 4 wires one at a time.
I then connect the other end to the mower headlight harness and then connect that to the battery.
This put the load of two of those lightbulbs on the wires. I tested each of the 4 ignition wires, one at a time.
Both bulbs were very bright with no dimming and all wires were the same brightness. While I do not know the exact amount of amp draw that was putting on the wires, I would have thought if there was a issue, that would have been enough of a load to bring it to light (no pun intended).

I put it all back together and crank it up. It fired off fine and kinda sounds like it was doing the missfire thing, but I did not rev it up. I just let it set and idle while I put up the tools and wires.
After running for about 5 min, I take it for a drive and it is running perfectly fine. I drive it up the road and back a couple miles with no issues.

So now it seems like it is going to do it intermittently, which makes it even more fun to find.

[MO LS Noobie]

Keep at it, you were fighting several issues. Start over as if it is a new situation. Still sounds like a ground issue to me. Voltage dropping during cranking, resets adaptive values, runs rough till it relearns.

[TriumphR3]

Possibly a ground, but I keep thinking back about an issue on my C1500 where a wire in one of the connectors at the ecm had worked itself loose and became intermittent. The truck ran terrible. This circuit went to one of the fuel injectors on the tbi. It was just dumb luck that I found it. I tugged on wires all over that truck. Replaced the ecm a couple times. Checked wires with a dvm. Finally tugged on the right wire and it reared its ugly head. Reterminated the particular contact and issue resolved.

Makes me wonder, if it’s consistent it’s usually ignition related. But when it randomly misses it might suggest fuel related.

[MO LS Noobie]

See my post #49 above. I've also had issues with customers wiring harnesses where it flexes and breaks the conductor inside but believes the outer insulation. I put about 5 pounds of stretching force on each individual wires, especially near the connectors. If it stretches the conductor inside is faulty. Regarding grounds they can look good but don't pass the high amperage needed. Voltage drop is the way to test them, but unbolting them and cleaning them with a wire brush, and putting dielectric grease on the connection is good preventative maintenance anyway.

[TriumphR3]

Fair enough Mo, I was just sharing my experience, thought it might be helpful. Shed some light at a different angle. No disrespect intended.

[MO LS Noobie]

Fair enough Mo, I was just sharing my experience, thought it might be helpful. Shed some light at a different angle. No disrespect intended.

None taken, we are all here trying to help each other. It can be very difficult to remotely diagnose the vehicle, especially one that is over 40 years old.

[JeepsAndGuns]

Again, sorry for such long times between posts/updates. Just been really busy between work, life, and other projects.

The alternator was mentioned a couple times in this thread. I had been having a random issue with it off and on for a couple months before the running issue started happening.
I would randomly smell burning rubber. The alt was still charging, but it just seemed like it was taking so much force to spin it, the belt was slipping. Pulley was burnt looking.
Every time I took the belt loose and spun it, it spun freely.
I even took it off and completely disassembled it, cleaned everything and lubed the bushings. No change, it would still slip and burn the belts (this engine uses dual V belts for the alt and compressor).
I ended up putting new belts on it with no change.

Finally I got fed up after working on it trying to find my issue and it decided to randomly do it and I got a face full of belt dust.
I bought a brand new (not reman) acdelco and put that on this past weekend.

No change in the running issue, but I have not had the belt slip yet. The voltage also recovers almost instantly when the radiator fan kicks on now, where before it took it a second.

While I was swapping out the alt, I had the battery disconnected, and I also saw a ground I had overlooked before. I checked and cleaned it. But no change. So all grounds have been checked and cleaned.

It is pretty much back to doing it constantly now. However it is a tiny bit different. It is so light at idle and driving down the driveway at no load, I almost did not think it was doing it. However as soon as I pulled out on the road and put it under a load, it is really noticeable.
When coming down the flat part of my driveway in 2nd gear, it is almost not noticeable, but as I start up the hill to my house, it starts doing it harder.
So it seems to misfire harder the more of a load it is under.

Lets go back to the topic of the distributor pickup. It was mentioned to change out the pickup AND the distributor shaft (with the reluctor wheel on it).
What was the reasoning behind that? It is just a toothed steel wheel is it not?
When I swapped to the 7 pin HEI distributor, I bought a aftermarket hei dist for the AMC engine, but it is made for a carb and had vac/mechanical advance. Strangely, the top is separate from the shaft/lower housing. I think it was so they could make the same top and lots of different shafts.
I bought a used complete 7 pin large cap distributor off ebay, and then chucked it up in my lathe and basically made a new top for the aftermarket distributor. The 7 pin module would not fit the aftermarket distributor and there was no way to make it fit (if you had saw it, you would know why).
Since the shafts were different lengths, I pressed the fuel injection reluctor wheel/rotor mount off the gm shaft and put it on the aftermarket amc shaft. I put a small tac weld to hold it in place.
Like mentioned in this thread, it has been flawless for years.
Can this reluctor actually go bad?



I am about ready to rip it all out and start completely over. However, if I was to do that, I would swap it over to a 12200411 ecu and get a brand new harness from a company that makes them for swapping LS engines into vehicles.
Strangely, the cam pos sensor would probably pretty easy. But the crank wheel and sensor will be the challenge. Mounting the coils on the valve covers should not be too hard either.