Ongoing 5.3 issue. Rough idle when hot after driving for awhile

[Sroka217]

Hi guys, looking for some help. I have a 5.3 that's become a real PIA. I've been chasing this problem for almost a year and it's now to the point no longer intermittent. Cold weather she runs great until after driving for 2 or more hrs. Hot weather sluggish after only 40 minutes. Flashing CEL ON highway while cruising after an hr or less. Flashing CEL at stop after 45 minutes of driving. Very rough idle and rich exhaust when it occurs.

Items replaced:

MAF twice

MAP twice

Fuel pump 3x

FPS 7x ( heard bad things about multiple brands and still can't hit 60 PSi)

Throtthe body thoroughly cleaned 4x

O2 sensors all the way around 4x

New Gibson exhaust-problem existed b4 n after

New Y pipe with cats

New exhaust manifolds

Intake gasket 2x

Fuel injectors 2x

Plugs 2x iridium and 4 point

Coil packs 2x

Ignition wires 7mm & 8mm

Tps sensor

Air filter

Fuel filter

Knock senor including new harness

Fuel lines, send n return

Alternator

Battery 2x

 

 

Current specs:

Fuel pressure while idle @ 50 psi

Fuel pressure KOEO- intial 58 then immediate drop to 51

Fuel pressure with blocked return line @ 85 psi

Leakdown @ 2 psI after 5 minutes, 5 psi after 12 minutes

ECT 91°C at operating temp

MAF normal

MAP normal

 

Anybody have anything similar to this? I'm hitting a dead end.

 

Next on the list is another compression test, vacuum test, oil pressure sensor switch, and oil change (again).

 

Please help and thanks in the future for your feedback. I know I can't be the only 5.3 experiencingthis issue. Oh, also to include when towing this happens to occur much faster.

[Sroka217]

I probably should add it's a 2003 chevy avalanche non flex fuel Z71 vin T. Regulators were replaced so many times since I found out my yr was produced during a production change for the regulators from on the fuel rail to in tank and supposedly GM was playing with the PSI on the part itself.

[O_J_Simpson]

Have you done a compression check hot and cold on Franken' motor?

[Sroka217]

That's next on the list. Have you heard of this freak of experiences before?