Engine backfires and sputters when floored

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Schurkey

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I made an assumption--which sometimes gets me into trouble--that his talk about doing it while stopped in neutral still involved whacking the throttle WFO. "Stopped in neutral" but not "idling in neutral".

IF (big IF) that's the case, the problem could still be a faulty TPS that doesn't provide proper signal towards the end of it's travel--inaccurate when the throttle is opened more than what's needed for normal driving.

'Course, that's not the ONLY possible cause.
 

greenz97

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See post #11, at 1st he said only at WOT, then later said it stalls at idle too. It's pretty hard to diagnose when you don't get the full story. :33:
I meant when I floor it in neutral I put a new fuel filter in because its cheap and needed one anyway the engine runs smoother now but i still have the issue.
 

HotWheelsBurban

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I meant when I floor it in neutral I put a new fuel filter in because its cheap and needed one anyway the engine runs smoother now but i still have the issue.
How does the truck idle? When the TPS went bad on my Burb, it was idling all over the place, fluctuating like crazy. Often the idle air control valve goes around the same time as the TPS. I replaced it a couple of weeks after the TPS, when the truck was idling weird again. Fixed the problem.
 

greenz97

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How does the truck idle? When the TPS went bad on my Burb, it was idling all over the place, fluctuating like crazy. Often the idle air control valve goes around the same time as the TPS. I replaced it a couple of weeks after the TPS, when the truck was idling weird again. Fixed the problem.
idles fine no issues there
 
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Not sure if I'm a day late and a dollar short....
I had a similar problem....I replaced the knock sensor in my pick up and verified timing and it seemed to solve the problem.
 

1996kbody

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I have a cammed 96 with a 5.7 I’m having the same issue when flooring it. Previous owner did know what came was in the truck. Any ideas were to start. Anything helps
 

Schurkey

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I have a cammed 96 with a 5.7 I’m having the same issue when flooring it.
Verify fuel pressure

Inspect/replace all "tune-up" items--distributor cap, rotor, plug wires, spark plugs, O2 sensors. Distributor caps are a known weakness of the Vortec engine.

Connect a scan tool, verify EVERY sensor and computer output.

How old are the intake gaskets? Another known problem of the Vortec small-blocks.

Was the cam "degreed" when it was installed, or merely crammed-in "dot-to-dot"? What is the cranking compression pressure of all eight cylinders?
 

1996kbody

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Verify fuel pressure

Inspect/replace all "tune-up" items--distributor cap, rotor, plug wires, spark plugs, O2 sensors. Distributor caps are a known weakness of the Vortec engine.

Connect a scan tool, verify EVERY sensor and computer output.

How old are the intake gaskets? Another known problem of the Vortec small-blocks.

Was the cam "degreed" when it was installed, or merely crammed-in "dot-to-dot"? What is the cranking compression pressure of all eight cylinders?
I’m not sure about how the cam was installed. I was told it needs to be tuned. The truck does not get enough fuel at high rpm’s.
 
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