[thomasgros1224]

i have a 99 silverado 4.8 2wd 240000 miles when i stop and then accelerate my truck boggs down and looses power. when it is cold it sometimes dies. i have changed the knock sensors the computer the o2 sensors and intake gaskets. it is slowly getting worse and i would love to find the problem if anyone can point me in to the right direction it would be a huge help

 

[majorxlr8n]

Do you have any power train codes popping up on the ECM (check engine light on)? If so, that's where I'd start. Could also be a low fuel pressure problem - has the fuel pump ever been replaced?

 

[thomasgros1224]

It has code for knocj sensors but i have changed them twice and i have already checked my fuel pressure and its good

 

[Gozzie]

That's why it's slow. It's retarded timing if it's throwing knock sensor codes at you. It may not be the sensors. It may be in the wiring harness.

 

[thomasgros1224]

What would cause it to retard timing

 

[Gozzie]

The ecu is protecting the engine from detonation. Of coarse this is just my opinion but there are quite few knock sensor posts out there. Do a little searching and you will find a fix.

 

[esox07]

The computer is reading a knock problem and compensates by retarding the timing. There may not be a knocking problem, but the computer thinks there is and adjusts accordingly. As advised earlier, check all the wiring to the sensors.
As long as your truck continues to read a knock sensor problem, it will continue to run poorly.

 

[thomasgros1224]

I changed the wire horness when i changed the knock sensors. There was a tap before i did that but i dont hear a knock or a tap. It runs smooth at idle and after i get going it runs fine until i get to a stop again

 

[Gozzie]

Are you still getting the codes ?

 

[esox07]

Very likely, you will have to get rid of the root cause of the knock sensor code. Until you do, the computer will continue to read a knocking problem and erroneously try to adjust which will cause it to run poorly.

 

[thomasgros1224]

Im still looking for the problem. I can use my scan tool to reset it but comes back

 

[esox07]

Until the ECU quits reading a problem with the knock sensors, it will continue to try to adjust. If the CEL and code keep coming back, then the underlying problem has not been corrected with new knock sensors and wires.
Let's go back to the beginning. What is the exact CEL trouble code that the truck is putting out?

 

[thomasgros1224]

P0332 and p0327

 

[esox07]

What brand of Knock sensors did you replace the old ones with?
If it wasn't AC-Delco, that is a good chance that is your problem.

 

[thomasgros1224]

It was ac- delco

 

[Gozzie]

Does it come back immediately after reset. Before truck is started ? After started ?After driven ?

 

[majorxlr8n]

are the knock sensors located near any engine accessory pulleys (ie: power steering pump, a/c compressor, alternator, water pump, AIR pump, belt tensioner)? if a pulley is loose on the shaft, or if the component is failing, it may "knock" - which in turn the knock sensor senses as an engine ping.