mr 5.3

my 02 started having a nice little miss so i pulled plug wires to see if i could find the miss nuthing really stood out .so i did the doller bill trick at the tail pipe and it would suck it out my hand ...i was told this could be a bad exhaust spring,bent valve of a bad lifter...anyone ever had one do this???its a bone stock truck no modds yet...but if i half to tear into it it wont be stock long...

TXsilverado

iTrader: (19)

take off the valve covers and see if anything stands out.

mr 5.3

yep...first thing in the mourning...

kelsey_canard

iTrader: (5)

If nothing shows under the valve covers, I would try a leak down test. I wouldn't think its a broken spring or collapsed lifter. More than likely those would keep the exhaust valve closed, and compression would end up in the intake. I want to guess a bad valve seat or something keeping the exhaust valve open.

53bowtie

iTrader: (6)

How would a broken spring keep the exahust valve closed? The spring is what closes the valve, if it is broken it will not longer close the valve.......

kelsey_canard

iTrader: (5)

You are right on the spring. I rushes through that post. Bad info. Bad lifter or pushrod would keep the valve closed, correct?

53bowtie

iTrader: (6)

Yes that is correct, if the rocker or pushrod or lifter is defective the spring will simply hold the valve closed with nothing to push against it to open it.

I wouldn't think a valve spring would be broken on a stock motor, although I have seen several of them broken on late 90's early 00's Mustang's so I guess its possible to get a defective one.

jszklany

iTrader: (1)

I had the same thing happen - ended up being a collapsed lifter. Best of luck to you!