1998 GMC Suburban 98 GMC 350 stalls, bogs down, hesitates o

Get some choke cleaner and clean the throttle plate on both sides as well as shooting some in the IAC. That causes a lot of stalling/idle problems. Then if you can do it, check the ohms of the crank sensor and cam position sensor. The sensors soemtimes don't set a code but aren't the best. If they read higgh ohms then replace them. ( Sorry I don't know the ohm readins on what is good or bad off the top of my head). Also clean the throttle plate shaft where it is by the throttle position sensor. I fyou do the shaft thing while it's running then you may have a vacuum leak and the computer is trying to cure the leak while it's running then you get driveability problems like you describe. The can of cleaner is about $3-4. Get CYCLO brand if you can find it as it's about the best i've used for years.

The only other thing that I can think of is that this truck has that plastic topped manifold. Other than a bad connection on top it may be teh injector lines inside the manifold that are giving the problem. Due to heat and time=mileage they tend to crack and leak. Another thing if you suspect the fuel pump it could have done two thing that I can think of the pump isn't on the line right or the wires to the pump in the tank are bad. One other thing I just thought of concerning your fuel pump your vehicle year has had fuel pump trouble as a problem. GM found that the harness oing to the pump was bad and when a delco pump was purchased in later years, they included a 11" piece of harness due to the original being screwed up and would give the problem of a bad fuel pump. As you have already replaced this pump and probably had it done at a repair shop you don't know what type it is. But if it was a delco there should have been a 11" harness installed due to the old one going bad. This could be your problem. If they installed the delco and not the harness then it's still screwed up and needs the harness as well. This happened in years1997-1999 in pickups/suburbans/tahoes etc. So check that. If it was installed then check to see if it is not instlled correctly. These are the only things that I can think of without haveing the vehicle to properly diagnose.