Unhook the battery, turn on the headlights, count to 10. Turn off the headlights, hook the battery back up. Turn the ignition to "On" (not start), count to ten. Start the engine, and let it idle. PCM will re-learn idle fairly quickly. Go for a drive. See what codes come back.

Given your symptoms though, if you still get a miss after it warms up for a few minutes, disconnect the front O2 sensor, see if it runs better.

 

Good morning & TY...just as you say, research tells me it's a sensor issue or vacuum issue or combination. My transmission man says the overdrive "shake" is from an engine miss. The second it hits the smallest downshift it goes away. My manual tells me there is a "connecter" on the firewall for a diagnostic tool. There is one there that I can't find anything else it could be for. We'll see how this 1st step goes. TY

 

Being OBD1 makes life interesting....... Not many folks have a scan tool for the older stuff any more. Might be worth while to see if you can't pick up a Snap-On MT2500 from ebay, or the like. Just make sure it has all the various adapters, and personality keys you will need.

 

Affirmative...TY... Follow the process it did reset with the expected 1-2... got rid of the 3-3 that it had prior but come back again with the 3-7..TORQUE CONVERTER CLUTCH SOLENOID CKT....(OPEN OR SHORTED CONDITION IN THIS CKT)... Now that may be an issue with the vibration in OVERDRIVE (that I posted about in an old thread from 2010 just now about OVERDRIVE SHAKE ??????)...But cant see how that is relevant to an engine miss....
HOWEVER...IN THE"VIBRATION" THREAD, a gentleman did say He Wound Up with a CYLINDER LEAK DOWN which apparently was an issue with his overdrive vibration... More or less causing a MISS... If I understood that right.

 

​​​​​DOES ANYONE KNOW WHAT THESE 2 "FIXED" CONNECTERS COULD BE FOR?
(1994 1500 2WD AUTOMATIC O/D 5.2L)

 

Blue one might be trailer brake controller. Does your truck have the towing package? No idea what the other one is.

 

The factory build sheet doesn't list a towing package, but who knows anymore... I thought 1500.00 was a steal for the truck but I'm thinking about, well, other things. Transmission Mount is broken found out this a.m. could be the shake from the MYSTERY MISS 🤔

 

My old 2001 2500 didn't have the towing package but it did have the blue plug to add a brake controller. There was another harness that needed to be installed but the harness and controller would give it the tow package.

 

I just came across something today... I noticed a vacuum line laying by the I believe it's the EGR valve (behind the throttle body) that was off of the EGR and had a spark plug stuck in the vacuum tube. I took the spark plug out and connected it back to the what I think is the EGR valve. It ran like crap. ... so I stopped and just pulled the vacuum line off of it and left it open and it actually runs a whole lot better...but it still has the miss of course. But it idles a little bit higher which is good. So wow what's up with that? Now it does and always has since I bought it run real Rich smelling, no black smoke or exhaust but smells real rich....
(I EDITED THIS SO IT MAKES SENSE NOW)

 

I bought a new compression tester to check the compression in the cylinder both wet and dry. Yeah I understand the compression rating for a new engine but how about a 5.2 with 200,000 miles what should the compression be taking that into consideration?