Poor acceleration

Tiny
GABRIEL GABRIEL BOLOGA
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 4.3L
  • V6
  • RWD
  • AUTOMATIC
  • 140,000 MILES
Rebuild the transmission. I replaced the fuel pump, . Injectors. Fuel pressure regulator. Spark plugs, wires, throttle position sensor. Checked rive 5 volts good ground and I still have poor acceleration. Last I do not have catalytic converters they have been removed. Please help! Any ideas?
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Monday, June 13th, 2016 AT 4:01 PM

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Tiny
CARADIODOC
  • EXPERT
Without catalytic converters, no change is going to take place in the composition of the exhaust gas, so the front and rear oxygen sensors will report exactly the same readings. That is what happens when a converter has failed and is what tells the Engine Computer to set a diagnostic fault code related to that failure. The Check Engine light will be on because the fault codes refer to something that could adversely affect emissions. With the Check Engine light on, you have no way of knowing when another problem is detected. More importantly, the Engine Computer knows it can't rely on the readings from the rear sensors to provide test results for some of the self-tests it runs, so many of those tests will be suspended. You could have a minor problem that might turn into an expensive one, but there will be no way to know which circuit or system has the problem without a fault code.

The first step is to replace the catalytic converters, erase the current fault codes, then hope a new fault code sets to direct you to the area that needs to be diagnosed.
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Monday, June 13th, 2016 AT 7:41 PM
Tiny
GABRIEL GABRIEL BOLOGA
  • MEMBER
Thank you for a response. The only code I have are P0420 and P0430 related to catalyc convertor. Before and after I REMOVE THE CATALYTIC CONVERTOR.I will describe the way dis engine sound like:when I take of from the stop it fill like the engine is working really hard and has very low pick up speed same in the highway when I try to speed up has a same filing. Thank you again!
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Tuesday, June 14th, 2016 AT 5:21 AM
Tiny
CARADIODOC
  • EXPERT
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
P0430 - Catalyst System Efficiency Below Threshold (Bank 2)

These codes are to be expected and are going to seriously impede any future running problem diagnosis. You'll need to install the converters and erase the codes before the Engine Computer can resume its tests that it runs constantly. Without a fault code to direct you to the circuit or system with the defect, there is no logical way to know where to start the diagnosis.

What you're describing sounds suspiciously more like dragging brakes. To check for that, stop on a slight incline, shift to neutral, release the brakes, then see if the truck creeps downhill on its own. If it does not, we'll need to look at the brake system. There are a number of common causes for dragging brakes.
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Tuesday, June 14th, 2016 AT 1:32 PM
Tiny
GABRIEL GABRIEL BOLOGA
  • MEMBER
Thank YOU.I been checked the brakes and no problems there. Really I am lost!
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Tuesday, June 14th, 2016 AT 3:49 PM
Tiny
CARADIODOC
  • EXPERT
The next thing is to use a scanner to view live data and see if something isn't right. Unfortunately I only know how the sensors are supposed to work and what normal readings are, but there is a lot more information available that I'm not good at interpreting.

One thing that is important on all vehicles other than Chrysler products is the fresh air tube between the mass air flow sensor and the throttle body assembly. There must be no cracks or other leaks in that tube. Anything air that sneaks in without going through the mass air flow sensor will not be measured. That will mess up the fuel metering calculations and the engine could starve for fuel. That includes other vacuum leaks.
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Tuesday, June 14th, 2016 AT 4:06 PM

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