Squirrely problem with #5

[BigBlocksRule]

1996 Vortec had a miss on #5. Plenty of fire and compression, every time I pulled the plug it was wet. Truck ran fine for a few seconds right after it was fired up cold, then it would start to miss again. Once it had been running, #5 would continue to miss, even on a restart.

Fuel pressure regulator was leaking into the intake, actually had a good bit coming out of the regulator discharge. It was hitting the intake on the edge of #5 runner, so about half of the leak was going into that cylinder. Replaced the regulator and she runs like a top.

Apparently there was enough fuel to flood the cylinder and once the plug got wet, that's all she wrote.

Pain in the butt but a cheap fix.

[muthstryker]

I have a misfire in cylinder 5 on my 97, there's a leak on the intake gasket need to replace the old one with GMs new designed gasket. Pita

[BigBlocksRule]

Get the whole kit, it's about $60 and is the ONLY way to get the metal gaskets. It will have everything for the top end if you work on that. While you have the intake off, take it apart and look for signs of leakage, mine was shiny clean from fuel wash, that was the dead giveaway. It's foul and filthy inside of a vortec intake. If you find signs that it's leaking, the regulator comes off easy with a retainer clip.
You can test individual injectors with the top half off of the intake. The big injector plug has to be plugged in, wiring harness ground has to be connected (front of the engine) and fuel rails connected. I was testing the #5 injector when I saw fuel dripping from the regulator and everything fell into place and made sense.

[speedygonzales]

Both of you would benefit from a compression test "DRY". Open the throttle all the way and disable the fuel system by pulling the FP relay and relieve the pressure.

BBR should check the oil for fuel contamination. You didn't mention you changed the oil.

[BigBlocksRule]

Oil was fine but changed it anyway since I'm about to sell this truck.
I'm assuming fuel wash/flood only happened at lower revs. Dropped my borescope through the plug hole and still see hone marks all the way around, cylinder looks fine.

[starterman99]

I had a random misfire on #5 usually on slight up hill or acceleration,tried everything I could think of cap rotor wires updated injectors,took it to chevy no luck. Finally pissed me off one day started missfiring pulling away from stop light slight uphill so I floored it. Bent the exhaust valve in #5 then I found out there was a TSB from chevy saying the valve guide clearance in some of the 5.7 vortecs was tight from factory and could cause random missfire. problem started at about 30,000 miles at 120 I finally found problem when valve bent. I was so frusterated I put a new GM motor in and did not even tear in to the old one for 6 months.

[BigBlocksRule]

^ the Tahoe we're replacing this one with had a bent valve in #2. It was way tight, I had it reamed and put a used valve in it and buttoned it back up. No signs of similar injector problems, though.