2000 GMC Safari w.O.T. Power loss

SCRAPPY1469

MEMBER
2000 GMC SAFARI
6 CYL
2WD
AUTOMATIC
153,000 MILES

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.

6 Replies

RASMATAZ

MECHANIC
75,992 POSTS

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

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Saturday, December 26th, 2009 AT 3:51 PM

SCRAPPY1469

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4 POSTS

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?

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Sunday, December 27th, 2009 AT 10:27 AM

RASMATAZ

MECHANIC
75,992 POSTS

Fuel pressure KOEO 60-66psi

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Sunday, December 27th, 2009 AT 1:12 PM

SCRAPPY1469

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4 POSTS

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.

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Sunday, December 27th, 2009 AT 6:55 PM

RASMATAZ

MECHANIC
75,992 POSTS

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