1995 GMC C1500 Low power

1995 GMC C1500
300,000 MILES • V8 • 2WD • AUTOMATIC
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K.P.
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Just bought this truck and it barely had enough power to roll down a hill, but it idled great and still does. If it was a "2" when we bought it, it's improved to a "6"now with the work listed below. Engine mechanical parts all sound good. Under hard acceleration it stumbles...you have to back out of throttle for it to pick it up speed. Have replaced plugs, wires, cap & rotor, and TPS. Cleaned and tested EGR. MP sensor tested good too. Checked timing with sensor unplugged and adjusted it to 0 degrees.

This thing runs good if you just let it get up to speed slowly. But when you can mash on it hard, it just coughs and goes no where. The only thing that seemed to help was adjusting the timing 10 degrees before TDC...the performance gets better, but it's still not powerful enough to pull a long hill or tow a boat. Any ideas please?
Jun 15, 2010 at 1:51 PM
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DOCFIXIT
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Do a compression test then post results
Jun 15, 2010 at 3:00 PM
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K.P.
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I ran the compression test and got the following results. They seem ok to me, but I need your expertise please. What is so puzzling is that after replacing the coil it ran considerably better but it is still just at about 1/2 power. Do you think it could be a distributor or ECM problem?

2 @ 140
4 @ 145
6 @ 150
8 @ 150
1 @ 158
3 @ 148
5 @ 160
7 @ 146
Jun 17, 2010 at 12:55 PM
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DOCFIXIT
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Has fuel pressure been checked 9-13 psi? compression a little low rather see 170+
Jun 17, 2010 at 2:52 PM
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K.P.
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Haven't checked that...will do and will advise...THANKS
Jun 17, 2010 at 3:54 PM
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