Ok, so I lied, it's a 93 Bravada but in february we put in a motor from a 94, still a 4.3 Vortec. AWD, Automatic. Anyway. About a week ago I got off the highway, 65 mph here in WiscANsin, and it started hesitating under load. It doesn't stutter in the High R's, although I just might not be hearing/feeling it. It shakes when it's stuttering, and it stutters all the time except, like I said, in the high R's. No CEL, no dummy lights, and my gas mileage really tanked, no pun intended. You can smell that it's running really rich, so I'm thinking the stuttering is because a cylinder is getting loaded and not able to fire correctly. So my first inclination is FPR. Anyone with .02?

 

Check the fuel pressure and what does it say?

 

Check the fuel pressure like mentioned, try cleaning the EGR as well

 

I have to wait til tomorrow to check the fuel pressure. I can rent the tool to do that at Autozone or a place similar correct? And what is this EGR cleaning? Is there an article on here somewhere or something? Thanks guys

 

Do a search. There plenty of articles dealing with cleaning of the EGR.

Your fuel pressure with Key ON, not Started should be around 58-62 psi. Turn the key off and the pressure should hold for at least 5 mins. If it drops quickly then your FPR is bad.