Hello,
my 93 Suburban K1500, 5.7 had the Cat cut out before I bought it about seven years ago. We've chased an occasional idle bump and some hesitation under load, replacing all ignition/electric components, dropping/cleaning the fuel tank, r/p fuel pump, filter, TPS. I had it analyzed and I've been told it's a fuel injection matter, and yes, the TB is in need of cleaning and/or rebuild (the injector pattern appears a bit narrowed, to me). Which brings me to the EGR Valve and Solenoid. My question is: Without a Cat, can the EGR valve--if it is inoperable or malfunctioning--cause any idle roughness or hesitation under load? Would it matter at all if I replaced them? Thank you.

 

Okay, that mystery is solved. I replaced the EGR valve today and yes, performance has improved, and I'll say more than somewhat. I still have a bit of a stutter occasionally, but not at takeoff, only when I ask for more at speed. Again, it's just a slight stutter, and I'm thinking that might clear itself up over time, after the computer gets used to having an operable EGR valve. I dunno, but I can say unequivocally that the new EGR valve seriously improved performance. Thank you.

 

Try running a couple of bottles of Techron fuel injection cleaner through it in one tank fill-up.