2000 GMC Safari w.o.t. power loss

2000 GMC SAFARI
153,000 MILES • 6 CYL • 2WD • AUTOMATIC
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SCRAPPY1469
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At wide open throttle engine boggs down badly. It starts right up and pures it even runs good most of the way through the throttle range if i apply the throttle slowly but if i mash the throttle to the floor it instantly starts bogging out. Scanned for codes and their are none. All sensors seem to look good. Checked fuel pressure and is o.k.. Checked vaccume and it is also good. I disconnected cat and checked but engine still runs the same. At this point i switched out injector assembly and still have same issue. I am A.S.E. certified and completely stumpped. Unfortunetly this is for a family member and i am making nothing off of it. Please help. If needed i can be reached at (260) 471-2277 monday morning at which time i will gladly give you a credit card # for your time. Thank you in advance for your help.
sincerely Alan S.
Dec 26, 2009 at 3:15 PM
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RASMATAZ
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Hi scrappy1469, Welcome to 2carpros and TY for the donation and selecting us as your auto repair site Feel free to ask questions at anytime and Merry Christmas and a Happy New Year 2010

Lets try testing the following below

Oxygen sensor
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
Dec 26, 2009 at 3:51 PM
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SCRAPPY1469
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thanx Razmataz but complete tune up done by brother before bringing to me. I checked to make sure wires were correct and their are. i also swaped out the injector. On scanner cam sync is reading -17 and should be reading 0. I checked distributor gear and rotor to make sure neither have spun and they have not. Could timeing chain have jumped and still run o.k. at partial throttle? what is fuel pressure at the rail for key on engine off? all sensors seem to read correct on scanner. help?
Dec 27, 2009 at 10:27 AM
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RASMATAZ
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Fuel pressure KOEO 60-66psi
Dec 27, 2009 at 1:12 PM
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SCRAPPY1469
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I removed t-chain cover to check chain and all is well. The reason for this is because when i mash it to the floor it boggs way down and starts popping and kind of lopeing through the air cleaner (like when a chain jumps a tooth). By the way the injector that i swapped in was brand new. So now we have replaced plugs, wires, cap, rotor, p.c.v., injector assembly, and checked the chain for wear or jumping. I am at a loss.
Dec 27, 2009 at 6:55 PM
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RASMATAZ
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You need to give me fuel pressure readings otherwise am gonna be lost just like you. I've given you an earlier suggestion dunno if you have performed it-if not start checking these are the possiblities
Dec 27, 2009 at 8:46 PM
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SCRAPPY1469
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Thanx for everything. Found bad P.C.M. glitching M.A.F. circuit. Swapped out computer and all is well. (so far anyway)
Jan 2, 2010 at 11:53 AM