1995 Sierra With Low Power

K.P. · June 15, 2010

1995 GMC C1500 V8 Two Wheel Drive Automatic 300000 miles

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?

rodram · June 15, 2010

First.... I would get the fuel pressure checked ... I think a TBI engine fuel pressure should be between 10 an 13 psi... there is not a lot of tolerance on the low end for good performance under acceleration

Mike G · June 16, 2010

If you don't mind me asking... How much did you pay and what so you plan to do with it? I know that when I had 190k on the factory build, I pretty much designated the truck for dialy driving and light duty. Seems to me that when you start putting a strain on the old buggy, you are asking for things to let go under stress. Just my thoughts of course...

--Mike

eddinger · June 16, 2010

sounds like the same problem I'm having. I found out that I had a bad injector, got 2 new ones on order now. But I fear that it is the fuel pump on mine. I am going to check the fuel pressure tonight, hopefully it checks out. Look for my post under the title TBI problems. A few people have great advice on it. If I get mine fixed and running before you, I'll post my results. One of my injectors was spraying fine at idle, the other was just a stream, or a trickle, until you give it gas. So I am replaceing it.