I have a 2004 Chevy Malibu. Bogs down and stalls with acceleration. Check engine light flashes. Idols fine. Changed the MAP as it had a P0101 code along with the P0300. Changed the plugs 3 weeks ago and started to run rough 1 week ago. What do I look for now?

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/

The belt tensioner is defective. It automatically keeps the belt at the proper tension. P0101 - MAF sensor (mass air flow sensor) or circuit problem. P0107 - MAP sensor (manifold absolute pressure sensor) signal is low.

Check for vacuum at map sensor.check fuel pressure.

sparkplugs have heat ranges, you need to stick with ac delco for those.

First check for any cracked pipes leading into the intake manifold If all OK (with no codes showing it probably is OK) try checking the fuel pressure regulator. If you smell fuel from the pressure regulator vacuum side arm (when the vacuum line has been disconnected) it needs to be replaced.

Check your catalytic converter, good chance that it has broken apart and is blocking exhaust flow. Common Chevy 4.3L Issue.

You have coil over spark plug ignition and one of your coils is bad.You need to find the bad coil and replace it.

The torque converter clutch circuit may be at fault. The best way to determine the problem is to have a scanner/computer to read check engine codes.

sounds to me you have a emissions problem check your EGR valve and MAP senser

I have an 04 Malibu and when I get hard starts when I'm in the car I just press the accelerator down about half way and it always starts right up, some times I have to hold the accelerator down a little after starting to stop it from stalling but it is rare.