5.7 Vortec question

[Phantom240]

Pulled my 99 Denali into the back yard car port today to start diagnosing my dead misses, and when I pulled spark plug wires 5 & 7, they were both dead. Being that they're adjacent to one another, would this point toward a blown head gasket? I'm not getting any of the other symptoms such as oil in the coolant, coolant in the oil, or pressure in the coolant system. I haven't pulled the spark plugs yet to see what they have to say, but is there anything else relatively non-invasive I can check out to help narrow things down a bit before I go and pop the head off?

 

[noJeepshere]

It might be as simple as the wires are going bad. Are there any codes associated with it? It could also be the distributor cap is going bad, even fairly new ones, I just replaced mine with only 30,000 miles on it.

Think about what else could be bad, don't just jump to the worst case scenario, you'll spend a lot of money and not fix what could be a simple problem. And blown head gaskets typically are very obvious, fluids where they shouldn't be, lots of smoke in the exhaust, fluids pouring out.

 

[Gzes]

Yea start with plugs n wires n cap n rotor. Cheap, easy, and sorta quick.

 

[SunlitComet]

stop....
remember you are dealing with a vortec 350. while it is possible you may have ruined the gasket like i did on mine (2&4) before that it had missing, backfire you name it because of issues with injectors(known long term issues). the dizzy cap can also fail in ways to wreck havoc. I would suggest since you have been driving it with say no fluid contamination, did I assume correctly?, that you reinstall plugs run your engine, use a spark tester on those two, pull all of them out right a way when done hold throttle wide open and do a compression test. do the misfires feel soft to you or are they head kicks when flooring it. do they ping or not.the results of all that along with proper description of plug visuals and smell should drop a deuce on the exact problem. if you are gonna blow some money lets do it right. should take less then 2 hours to do.

---------- Post added at 03:47 PM ---------- Previous post was at 03:45 PM ----------

And blown head gaskets typically are very obvious, fluids where they shouldn't be, lots of smoke in the exhaust, fluids pouring out.

you could blow a gasket on these with no fluid contamination or leakage.

 

[Phantom240]

I've only driven it a total of about 1.5 miles, when I bought it at an auction on Thursday. The cylinders are completely dead when it comes to combustion. Being that I know nothing of the truck's previous life, and there was a water bottle in the engine bay, I have a pretty strong hunch. As far as injectors, I know they're flowing because I can smell fuel in the exhaust. They make be stuck open however. I was going to do a compression test tomorrow and inspect the plugs while i have them out. Contamination should be pretty obvious at that point.