Hello, I am having an issue that I cannot trace down the source of. I am getting a slight hesitation (about 1-1.5 seconds) when pressing the throttle coming off of a full stop. The idle is smooth, acceleration is fine once the hesitation corrects itself, and it never has acceleration problems once out of a stop. Plenty of power when cruising at any speed, it's only the slight hiccup when starting up from a full stop.
Some history:
2003 TB LTZ, 4.2 LL8
Purchased the vehicle with 86k miles with a blown engine. Swapped in an 75k engine. Used original throttle body (OEM, thoroughly cleaned) from blown engine, all new sensors (crank, ECT, both O2's, etc... All are ACDelco/ Delphi, nothing off brand), did the crank relearn.
New fuel pump (ACDelco) & wix fuel filter, fuel injectors (genuine Delphi), fuel pressure regulator (Delphi).
New plugs (ACDelco 41-103), new coils (Denso)
I switched the throttle body with another used OEM, did the pcm relearn (pulled PCM fuses for 2 hours), same result. Both throttle bodies have been THOROUGHLY cleaned.
I am at a loss what to try next. Idles perfectly fine, though pressing the peddle when in park has the hesitation as well. The only issue is directly from a stop or sitting and idling, never anywhere else at any speed, kicks down and has plenty of power everywhere else. If I his the throttle aggressively from a stop, it happens slightly less, but under normal acceleration it is quite noticable. It has never died, it catches itself before that, but it's still something that needs to be addressed.
Thanks in advance for any assistance!
Some history:
2003 TB LTZ, 4.2 LL8
Purchased the vehicle with 86k miles with a blown engine. Swapped in an 75k engine. Used original throttle body (OEM, thoroughly cleaned) from blown engine, all new sensors (crank, ECT, both O2's, etc... All are ACDelco/ Delphi, nothing off brand), did the crank relearn.
New fuel pump (ACDelco) & wix fuel filter, fuel injectors (genuine Delphi), fuel pressure regulator (Delphi).
New plugs (ACDelco 41-103), new coils (Denso)
I switched the throttle body with another used OEM, did the pcm relearn (pulled PCM fuses for 2 hours), same result. Both throttle bodies have been THOROUGHLY cleaned.
I am at a loss what to try next. Idles perfectly fine, though pressing the peddle when in park has the hesitation as well. The only issue is directly from a stop or sitting and idling, never anywhere else at any speed, kicks down and has plenty of power everywhere else. If I his the throttle aggressively from a stop, it happens slightly less, but under normal acceleration it is quite noticable. It has never died, it catches itself before that, but it's still something that needs to be addressed.
Thanks in advance for any assistance!
