[AllanC]

. . . . I have this 92 Dakota with a 5.2. This truck has been a topic of discussion here before.

after I got a the bugs worked out the truck has ran great until recently it's been acting up. I'm betting because of the colder temps we have been getting in Tx.

So here's the issue. Truck starts up and runs perfectly fine until you shut it down and come back after 15ish minutes then it runs like it has a huge vacuum leak and runs very rich strong fuel smell. After 2-3 minutes of this it just goes back to normal.
It's only after the truck has completely warmed up and only when it's been shut down for 15 or so minutes. Only in that particular window of time. And will always go away after a couple minutes after start up. . . . .

I would suggest you have one or more leaking fuel injectors. At engine shut down, the fuel rail maintains operating pressure for a long period of time. If an injector(s) is leaking, raw fuel is being dumped near the intake valve. After a 15 minute wait, at engine start up this raw fuel can cause erradic running because of the overly rich fuel air mixture. Now if the engine sits for a longer period of time (1 or more hours) the raw fuel dump has a chance to evaporate and there is no overly rich fuel mixture at engine start.

Connect a fuel system pressure tester to the fuel rail port. Run the engine to operating temperature. Shut off engine and monitor the fuel pressure. If it starts to drop over a 15 minute period you have leaking injectors.

I would perform this test before randomly firing the "parts cannon" and replacing oxygen sensors or engine coolant temperature sensors.

 

[AllanC]

. . . .That's a good theory but I doubt enough fuel could evaporate in 10-15 minutes time (after the initial 15 minutes) to run perfectly fine. I have run multiple test after test runs and it's always plus or minus 5 minutes of the 15 minutes after a warmed up shut down. . . . .

I would still suggest you perform the fuel pressure leak down test. You can rent / borrow a fuel system pressure tester and not cost you any money. Perform the test and if the pressure holds then you have CONCRETE proof that there is no fuel injector leakage. Then you can move on to other theories or tests.