Something wrong: 5.3L Engine losing strength
 

Hey, my dad has an 02 5.3L Sierra Z71... About a week ago the truck started to seem weak, and a rapid clicking/knocking noise would sound when accelerating from 30 to around 50/60.
Now, after about a week, the problem progessed to the point were, when you creep from a stop, instead of rolling slowly, the truck jerks... Acceleration takes forever, even getting up to 45 takes quite some time... It idles and runs jerky, and makes a louder (throaty) during normal acceleration. It's to the point where we don't want to drive it anymore, fearing it will break down.

The SES light has been on for a while, but haven't had time to check it (hopefully will be borrowing a scanner tomorrow). Now, the SES light flashes when the truck starts to jerk while accelerating...

He suspects the flexplate may be cracked (causing strange knock sensor readings?) or the cat could be clogged? Any ideas?

PS: The clicking noise kind of sounds like spark knock... More of a ticking, I guess.

Thanks in advance,
-Kevin

RE: Something wrong: 5.3L Engine losing strength
 

sounds like you have a cracked valve in the head, check the tail pipe and see if thers any fresh oil in it. just run your finger around the inside of it. If thats not the problem then it might be a flat spot on the cam, chevy's go threw cams faster then any other vehicle ever produced.......and thats not the ford fan coming out of me either lol, honestly cant realy tell you without hearing it but thats what it sounds like to me 1 of those 2 things i said cam or head valve cracked.

RE: Something wrong: 5.3L Engine losing strength
 

the reason i say the valve might be cracked is cuz they give off alittle knocking noise that is a backfire inside the intake kinda like a spark nock
its realy hard to tell you man without hearing and experiencing the problems you are describing.

RE: Something wrong: 5.3L Engine losing strength
 

K, tomorrow I'll have to check, I know when you put your hand infront of the exhaust you can feel it pulsating alot more than normal...

PS Its a GMC...