94 chevy 5.7 2 wheel drive

Forgetting all you have done & why

What is or was the main issue & when did it start
& under what conditions ?

Does the thermostat open ?
Does it reach 195 or more coolant temp?
Does it go into Closed Loop? (Oxygen Sensors
in control of fuel)
Any OBD Codes in any system?
Fuel Pressure Correct as well as Volume
& under a load while driving

Sounds like you were going to say it only has a problem
AFTER it reaches operating coolant temp

SO- none of what you did appears to be related

First-- you find & resolve all problems. THEN do your
Preventative Maintenance-spark plugs,filters,etc.

Check or test the switch on the transaxle, that is for gear
selection,whatever you have there

May be the only problem you ever had or one of two problems

Only runs when cold-- in park only?
Won't run hot or cold-- in ANY gear?

Can you even drive it at all?

How about an Idle air control solenoid/valve
on or near the throttle body-got one of them?

Pull the air cleaner off and crank the engine. If puffs of air come come out of the throttle body when cranking the engine then the timing is not set correctly. Otherwise, after cranking pull a spark plug and see if it is wet with fuel and if so this indicates an ignition problem (coil, distributor/cap/rotor or faulty ECU).

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/dave_fb2c45146b845cea

Does the truck seem fine when you first start it & then acts up when it reaches operating temp?
That would lead me to look at my oxygen sensor, a bad sensor can cause the truck to run "rich" which would explain the fuel smell in the exhaust.

When it stops running and will not start back up, you'll need to figure out if you are lacking spark or fuel pressure to proceed with testing.

Have u checked the cadeletic converter. It can do funny things

could be clogged fuel injectors or fuel filter could be plugged or your fuel pump is weak and needing replaced,what makes fuel pumps go bad in most vehichles is driving with less than a 1/4 tank of gas,it gets the fuel pump hot and works it too hard

First you need to retrace your steps...before you changed the timing chain and gears did It run ok ? what was initial problem, next put a fuel pressure gauge on your fuel line and cycle your key on to run pos, dont have to try start, just run and see if you have fuel press during the 3 sec or so pump cycles, should be around i think 35-45 roughly for tbi. so if you have good fuel pressure , then you say you have good spark, then your problem is either ingition or valve timing, did your dist.come loose, did you properly install chain & gears and align timing marks. did you have somethine else a part on it too like intake, dist, ? get back with me I'll try to help you.

CHEEK FOR BAD PLUG WIRE DONT TAKE MUCH AND TRY THIS AFTER DARK CHEEK UNDER HOOD U CAN SEE THE SPARK BETTER SOUNDS LIKE IT JUMPING FIRE I HAD A GRAND PRIX 73 MODEL WHIN I WAS YOUNGER IT DID THAT I LOOKED UNDER HOOD AFTER DARK MAN IT LOOKED LIKE CHRISTMAS TREE BAD WIRES WILL MAKE IT CUT OUT GO BYE SOME FROM NAPA I BET IT WILL CHANGE IT IF ITS FULL ING TRY CHANGING YOUR TPS SINCOR AND ANORHER THING FROM WHAT YOUR SAYING SOUNDS LIKE IT MAY BE JUST A TAD OUT OF TIME LOOSEN THE NUT UNDER THE DDISTRIBUTOR TURN CLOCK WISE JUST A LITTLE SEE IF IT GET BETTER

my buddies 94 350 has been doing the same thing for years i think its in the computer i would say youll probably have to live with it

idle air control motor on back of throttle body maybe malfunctioning and not allowing it to idle