HELP! 98 Camaro z28 stock ls1 that's has been rebuilt with only 11k miles. Has a tune, gears, stall, and a lid. Cruising on the hwy and all of a sudden started missing. Misfire is on cylinder 2. Didn't run hot, checked/swapped spark plugs, swapped injectors, oil and coolant not mixing or milky.. What now?

About two months earlier, the engine temp sensor failed and the car ran hot and wouldn't start. I could see a very small amount of steam/bubbles on the top left side of the intake in one small spot. It was towed home, I parked it and didn't mess with it until I replaced the sensor. It crank and drove fine up until now. What do you guys think??

 

Could be a bad coil. I had one that would miss at idle and part throttle but worked fine at WOT.

 

I'd check compression 1st.

 

Start with the simple stuff.
Swap the spark plug wire with another cylinder.
Then you have the spark plug, coil, injector.
Does it misfire when hot, cold, at idle?
You can gently move the coil wires, or the injector wires for cyl #2 to see if that affects a change.

 

Sounds like you've already eliminated the simple stuff.

You said it cranked and drove fine; for how long?

If the temp sensor failed, it won't cause the engine to run hot or overheat. If it got hot enough that it wouldn't start, that usually means bad things are happening.

What do you mean by steam/bubbles on the intake? There's no water there (normally).

As said above, I'd do a compression check. Follow that with a leak down test, and check the coolant for byproducts of combustion.

 

The electric fans wouldn't come on until the sensor was replaced...

It misses whether hot, cold, or idle...

It ran fine for over 2 months. It all of a sudden doing this and it began missing while I was cruising on the hwy.

I don't know if they checked the coil but as stated the plugs, wires, and injectors have already been checked/swapped.

A compression test is in the works. I picked up another ls1 (bottom end issue) today for free from a friend with some 853 heads on it so they may be getting a little work done to them and a cam swap. My car is a 98 and these heads are off of a 2000 I believe.

 

There was a section about an inch long on the left side on the top of the intake where the heads and intake are aligned where I saw the small bubbles/steam "sizzling." This was the first time I had the issue with the SENSOR when it ran hot. I mentioned that because it puzzled me and wondered if it could related or maybe an intake gasket issue.