99 yukon 5.7 vortec misfire HELP

[ccapehartusarmyINF.(ret)]

i checked it out 95 was the last year for the flat tappet cams 96 and newer motors are all hydraulic lifters and roller cams
but like i said worse case scenario its possible with a motor with 216k miles its possible that its a bad valve spring or bent pushrod broken pushrod cup in rocker arm causing the valve to float

 

[SunlitComet]

Be positive!

 

[OR VietVet]

If the engine had bad/bent/broken valve or springs or rocker the problem would be apparent right off the bat on start up.

 

[ccapehartusarmyINF.(ret)]

ehhh if yer valves floating becuase of a weakened valve spring most of the time you wont se symptoms untill higher RPMs

 

[OR VietVet]

Agreed but instead of separating out the broken possibility I just lumped it all together in my post. Broken bent will likely show asap where as weak may take a bit.

 

[ccapehartusarmyINF.(ret)]

gotcha sorry to nit pick
this brings up another interesting quesiton when is a good time to change yer valve springs how many miles are they typically good for

 

[OR VietVet]

I don't think I have ever changed them as a maintenance item unless I was having problems and then they were diagnosed as the problem or when heads are off and at the machine shop the tech tested them and said were needed.

 

[lifted_yukon22]

Ok I work at night I will try to get up early next week and go get it scanned for the history. I may go ahead and buy the Delphi mfi since it would be better in the long run.

 

[ccapehartusarmyINF.(ret)]

thats kinda what i thought but then when i was researching floating valve symptoms i came across posts by dudes on other forums claiming valve springs were only good for like 60k miles and i was like WTF thats a newone on me one post even said they needed to be changed every 30k miles

 

[lifted_yukon22]

http://m.ebay.com/itm/321566658857 ok this scan tool lists a misfire monitor will thst find out my misfire history?