Truck runs clean and smooth, changed all electrical and fuel components, I get good fuel, replaced throttle body, jets. everything that I can think of
If that's all you have to offer then I would say your map sensor is bad...
SOURCE: My 91 suburban does not
I have a 91 suburban and it wont hold idle. I am waiting for and egr valve. if that fixes it i will let you know. I was told that they can have an internal vacuum leak therefore being difficult to detect.
SOURCE: 99 gmc no power when passing or climbing
It could be electric fuel pump stall. The pump isn't pumping fuel fast enough. This model may have a inline fuel filter before the fuel pump as well that might need replacing.
SOURCE: 99 gmc no power when passing or climbing
It could be the cat. it sounds like this could be your problem
SOURCE: 95 GMC Sierra 4x4 350 5.7 rough idle problem
It sounds like a MAP sensor going bad. MAP is short for manifold absolute pressure sensor, it senses the manifold pressure and applies the right amount of gas with the right amount of ignition timing so the car runs and performs well if this does not work properly. It throws off the whole loop cycle for the computer, which in turn makes it run badly and get poor fuel economy. It can causes the engine to have a lack of power, combined with a loss of fuel economy. Poor take offs and sometimes an occasional stalling may occur if the MAP sensor is faulty and sending the wrong signals to the ECM.
Hope this helps and thank you for using Fixya.
Here is a link that my help you in the future.
http://www.troublecodes.net/GM/
SOURCE: Truck will turn over but not start. Checked fuel
The ignition module located inside of the distributor is what generates the signal that the ECM (Engine Control Module) uses to time and fire the fuel injectors, as well as the signal to run the fuel pump and the dwell signal timing to fire the ignition coil. A faulty ignition module can cause any one of these systems to malfunction.
That does sound like a malfunction with the ignition module inside of the distributor, and you can remove the ignition module and have it tested for free at most auto part stores.
If you do purchase a new ignition module be sure that it does come with a silicone grease or a die-electric compound because it is a heat sink and the ignition module will burn up without it.
To install the new ignition module first clean out the mounting surface inside of the distributor. Then completely coat the metal contact surface under the ignition module with a thick coat the silicone grease or die-electric compound and do not leave any of the metal contact surface of the ignition module un-coated with the silicone grease or die-electric compound, and be very careful not to over-tighten the ignition module or it will be damaged.
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