5.7 engine troubles

[maxbencher]

hey all,

My 95 z71 with 5.7 tbi runs great at lower speeds, but when I push the gas pedal down hard and it shifts into passing gear,my engine revs and the tranny downshifts but I lose power . I have changed fuel pump, fuel filter, knock sensor, sparkplugs,distr. rotor,checked timing, I keep checking the fuel line pressure and it stays at 13 psi.I don't get any codes on my truck. I'm going to continue to keep checking things out, but if anyone knows of anything it would be appreciated.

[twomorestrokes]

The '95 TBI certainly is no powerhouse, but if you've had the truck for awhile, I'm sure you know when something's not right. My last truck was a '95 K2500 TBI. How's your catalytic convertor?

It may be helpful to drive it with a scanner plugged in if you know of anyone that has one. That way you could watch the timing advance/ retard etc etc etc while it was acting up. I had an engine once that would fall on it's face above 3000 rpm, and the scanner showed the timing pulled all the way back while it was occurring. (The knock sensor was picking up an inaudible main bearing knock)

[maxwedge]

Hey Maxbencher, refers to your workout specialty? Anyway drop the exhaust down somehow in front of the cat and drive it see what happens, remember find a isolated area, cvould get a ticket here.

[2000CAYukon]

I recently had some issues with my 90 K1500 5.7 TBI where it seemed to have lost some of it's low end torque. In my case, the timing chain had a lot of slack (timing mark would jump around while timing the engine). The new timing chain helped but I later found out that the MAP was bad. With the new timing chain and MAP, the low end came back.

The MAP detects load and increase fuel based on engine load so make sure that it is getting vacuum and that the MAP holds vacuum (using a vacuum pump).

Exhaust can also cause no power so be sure to check that out (as posted above). Exhaust, fuel delivery (MAP included) or mechanical (timing chain).

Good luck and post back any updates.

//2000CAYukon

[maxbencher]

thank you one and all for the advice, I will check on all of these and will let u know if anything changes good or bad