My Echo-225 bogs down and stalls out once I pull the trottle down. changed gas out and put in premixed 50:1 fuel and let it idle for 10-15 minutes. Pulled down the trottle and stalled out each time

K1500 PICKUP. ? 5.7 TBI. GAS
i will assume eng. compression good and spark good and timed by the book.
it's staving for fuel.!
fuel pressure not at spec,
fuel pressure regulator bad.
injector clogged (injectors screens inside packed)
bad fuel (was bad now bad fuel is in all that path)
MAP sensor bad or clogged up. EGR stuck open
meter mAp pin out,1.5vdc out,keyon to 4.5V WOT (wide open throttle)

we test fuel pressure 3 ways
key pressure
idle
and WOT
the manual covers that, buy the service manual?
so the pressure specs for TBI are at hand./?
there is no fuel rail like MPI so has very odd connections to do pressure tests TBI. (below)
you do know most injectors have 10micron screens inside,and only ultra sonic reverse cleaning cures them right? (or new injectors) I send mine out for pro cleaning, (Usonic)

the hard part of 1995 TBI is getting the TBI specs.
the manuals were 500 pages paper and nobody digitized all page or skipped most the Injection pages.
it is a problem but the used books are sold at EBAY
from GM (real)

rumor has it
"In stock form a tbi operates 11 to 13 psi running a bit higher makes them run better to a point of about 14.5"
the TBI if you look close has a FPR, seen here
it must be good.(diaphragm)
some TBI have 2 injectors, start+idle (and fast run)
as seen here

https://www.rockauto.com/en/catalog/chevrolet,1995,c1500+pickup,5.7l+v8,1031443,fuel+&+air,fuel+injection+pressure+regulator,6124


next up how to read the pressure (tap ports)
I think this is a returnless system (early)
so they make up filter tap point. fuel. or TEE fitting.


https://www.reddit.com/r/MechanicAdvice/comments/10nz5rd/best_way_to_check_fuel_pressure_gm_tbi/

Have you checked at all the fuel pressure or the fuel pump?

Your only problem friend, is the temperature sending unit/sensor. Upon cold start, this sensor wil tell the computer to go into cold start mode putting a bit more fuel in and raising the idle a bit to keep it running when cold without using the throttle. Replace that sensor and your good to go. Makes sense, right?

Have you tried changing the fuel filter?

Probably fuel filter. That's where I'd start.

Check the trottle body postioning sensor...

have you ever had the injectors checked. if not try runing some fuel injection cleaners through it and see if that works

Check the air filter hose. My '99 Protege was idling rough and would sometimes shut off. The air filter hose was cracked half way around. I replaced it (easy just loosen two hose clamps and pull out the sensor) and the car is running fine.

Don't know if it applies to your diesel but most later gas engined vehicles have a 'cold start' valve that supplies additional fuel to the fuel/air mix along with boosting the idle speed until some warming of the engine is sensed.

Even though this is an old post i feel it needs an answer since there is 225 followers wanting an answer. This situation sounds as if this vehicle is either suffering from the Throttle Position Sensor switch which has bad spots in it causing lack of voltage or the Fuel rail pressure regulator which can not keep the fuel pressure built up in the fuel rail making the auto veel like it is running out of fuel.And the transmission speed densor which also controls fuel. The situations for each device has a test that can be done to determine which one it is. And last but not least lets never forget our fuel filter this can cause the exact same problem. I am eliminating the cam sensor because it stabilizes at idle. Eliminating the crank sensor because it too at idle also stabilizes and returns a smooth idle. So a fueling problem is what we have here one of the above. Enjoy and if you need help determining which one just ask me I will help you figure it out. Please rate my advise thanks it is how i receive my achievements.