I have to admiit I'm a novice when it comes to engine internals...I've got an '04 LS6 longblock swap in my '98 Z28 that's been running fine for 9 years. I've been chasing an intermittant miss lately at idle, WOT, and regular driving. ATap was showing intermittant misses on cyllinders 1 & 6, but it's very minor. I'm still not convinced it's not a cat going bad and/or fuel pump/fuel filter problem. All I know is I can feel it stumbling and it has slight "pop" backfire after it's been idling for 5 mins. or so. I've been reading horror stories of valve springs breaking and dropping valves, so I actually decided to take the valve covers off and take a look so that I can have piece of mind that I can run the motor while I chase the miss down if it's not a broken valve spring.

I can't find any obvious broken valve springs, but the one in this picture did catch my attention slightly...but it just may be the end of the last coil and it's normal. Please zoom in and take a look at the base of the spring and you'll notice part of coil sticking out slightly. It also appears that the retainer is cocked slightly at the top, but then the spring also seems to be compressed, so it may be normal. Is this a perfectly healthy valve spring and it's OK to start with the obvious things like plugs/wires, etc. to try and track down the miss?

I appreciate your time! Thanks!

(I've got new plugs/wires, cleaned the MAF, and replaced the 02 sensors with new AC Delco sensors...No codes have been thrown, but I did have a pending code for the O2 heater on Bank 2, Sensor 2, so that also makes me suspect it could be the passenger side cat if everything else checks out...Next up is going to be a fuel filter change...)

 

No one has any thoughts? .......

 

It looks okay to me. Turn the engine over and see if you notice anything moving that shouldn't be.

 

Does it start right away when you turn the key?

 

Some have seen vs issues with ls6's. Usually over 80k on them. I changed mine to hopefully avoid any issue with that.....but I turn it 7000 also....a little harder than most. Other than that do the basics first, plugs/wires/fuel filter/clean the maf. Please post up what you find.

Try pushing on the vs by hand. They can be very easy to overlook.

 

I think I see what you are stating ,maybe install new springs.also swap you coil and plug wires around .get new plugs .check your push rods for straightness .

 

I strongly doubt its a FP or Cat issue. Neither one of those will cause a single misfire. You would have REM codes and too lean codes with the FP.

Ive only encountered 1 broken spring ever and that was on a old Porsche 914. Its symptoms were a 100% dead miss. The spring was snapped in 2.

What you need to do is hook up a vacuum gauge while its running (and misfiring) and check to see if the vacuum is bouncing. If its bouncing you could be having a valvetrain problem.

 

I have seen random misfires from broken vs's. You could even change the plug and it would straighten out a bit. That car taught me to not count anything out....lol

 

looks broken, any others look same?are they single or double, I run double and after only 12-14 k mile, about 10 years I had 7 out of 16 inter only break into 2-4 peaces
Johnny