Curious what happens when you break an intake stud (darnit) and keep running the engine?

Here's what happened, you make the call.

Driving to work, (25 mile trip, about half freeway half city streets) get to within about 10 miles. All of a sudden, engine has an obvious miss, but only obvious at lower RPM's. Figure probably a burnt wire.

Keep driving, about 5 miles from work, miss has gotten worse, any attempt to accelerate at any engine speed is met with what sounded lik backfiring in the intake, and lack of power. Check engine light comes on for about 1 minute, then shuts off. Idle quality now poor.

Notice right about now that the passenger bank (trew dewls) has started smoking but not at idle, only under acceleration. Looks white, dang, thats not good I think to self.

Smoke gets denser as I get closer to work.

Pull into parking stall, set e-brake (manual trans) pop hood, and jump out. Nothing going on under the hood, but by now there is a lots of smoke/steam whatever, coming out of the passenger exhaust. (although I did also notice a fairly distinct tapping noise from the valve cover vicinity on the passenger side)

The exhaust wasn't "wet", and did NOT smell like raw fuel OR unburnt coolant. Coolant level was fine after I let it cool down, didn't seem to have lost any.

After work popped the valve cover off (only because I knew that was something I could figure out pretty easily) and sure enough, #6 intake rocker arm stud had broken. All pieces still in place, but the rocker had been tapping the valve cover a bit.

Now I still think it almost HAS to be coolant, but I got to thinking. If the engine continues to run, but the intake valve never opens, does the runner just fill up with raw (or vaporizing) fuel as the injector keeps injecting? If it does, perhaps I got "lucky", and for whatever reason, the smoke was excess fuel that A) didn't smell like fuel and B) came out white. (I don't see either being possible of course)

However, the code that the ECM threw was for rich exhaust, so there was obviously unburnt fuel. (the below may partially explain engine code though too)

The only other odd piece to the puzzle, is that when I pulled into the parking stall, and popped the hood, I pulled first the #2 wire, then #2 and #4 at the same time...pulling one or both didn't affect idle quality at all, indicating a dead cylinder for whatever reason.

After letting the engine cool, I restarted it. Idle wasn't perfect, but not as bad as the first time I shut it down, there was no smoke out of the tailpipe, and pulling #2 or #4 plug wires affected idle quality.

No oil in coolant or vice versa. Oil level was fine, although I didn't check oil for fuel smell.

I must not be the ONLY person that has lost an intake stud and kept driving, curious what anyone elses experiences have been. But thoughts and speculation are of course welcome.

I obviously have to pull the head, and I will have all the studs pulled and drilled/tapped for screw ins. So even if it were a head gasket, it will be fixed. I'd just like to know what could possibly cause what I experienced after the stud broke in the first place.

 

I've actually dropped an intake valve, or more correctly the head broke off. I've also pulled pressed in studs out of the head. Even bent pushrods, all the same result, intake valve not opening. As long as it didn't pop the lifter out you should be able to replace the stud and be fine. The white smoke I'm not sure of, I'm guessing that if the car was throwing a rich code it leaned it out trying to compensate as white smoke usually means a lean condition.