So two days ago I was driving home and began to notice a hesitation when accelerating. In addition to the hesitation I noticed some sort of odor, I could not pin point it at that time, but kind of like something burning. I have since started the car a few times and it smells like a burnt out firecracker or rotten eggs. During this episode the SEL came on. I noticed it would flash if I attempted to accelerate hard. Checked the manual (I had not seen this before) and realized it indicated a misfire. I got the car home and indeed scanned it for a P0300 cylinder misfire (does not indicate the cylinder). That is where I began my search on this site to help troubleshoot this. I have gone through a few things on suggested from the site but am still looking for any additional advice that people might have.
Below is what I have done so far:
1. Checked all wires resistance, checked at around the 3,000 ohms mark (a little higher for the longer ones).
2. Checked the resistance at the coils, this checked at about 5.5-5.7 on all coils.
3. Pulled the three "easy" spark plugs (front ones) and did not notice any issues with them. Spark plugs were replaced with standard Bosch Copper plugs 20k miles ago (along with the wires (AC Delco, I believe).
4. I went to start the engine at one of the many instances (after sitting for awhile) and it chugged a bit to start, so I began to check the fuel system. First checked fuel injector leads with Noid lights, all looked good.
5. Checked fuel pump pressure, and was around 42 PSI, all good there.
6. Checked the resistance in all fuel injectors and measured 12.7 ohms for all.
7. My wife last put gas in the car and put in the mid grade. I have done this before with no issues on rare occassions, but typically use the 93 Octane. Due to this I filled up with 93 Octane, but have not driven enough to "cycle" that fuel through.
8. I have ordered a fuel filter to replace, as I am due, but I am not convinced this is the issue.
Some additional things to note:
1. In the past month my electronic leveling has not been working so I have been running with the relay removed after I am satisfied with the level of the car.
2. On a couple of occasions (not every time) when starting the car I get the items highlighted below (all at once):
a. Air bag service
b. Service Stability system
c. Service theft system
d. Security light is on
e. SEL light is on
f. no reading for tire pressure monitoring system
3. Upon first looking at the engine I noticed that my coolant reservoir was below the level to feed the engine.
4. Still notice some sort of odor while the car is running (firecracker/rotten egg smell). This order is noticeable from the exhaust and at the engine compartment.
5. Water (or some liquid, feels and looks like water) drips from the exhaust while running.
6. It also appears like there is some "liquid" (looks like oil to me due to viscosity and if it was fuel, I would assume it would evaporate fairly quickly) around fuel injector for the 5th cylinder. Also further in behind the fuel injector for the 3rd cylinder, there is a small area of liquid that I can't quite get too (again, looks like oil based on the viscosity and lack of evaporation). See attached pictures for this.
7. I also noticed a rattling on the idler pulley for the belt that runs the back belt (non supercharger belt). See video at the following link:
I am looking for some additional things to check. I am almost to the conclusion that it is my manifold gaskets that need to be replaced. I last replaced them 40k miles ago while changing to green antifreeze. I used a Fel-Pro gasket. I am just hoping this is not the case, again, but I am not looking forward to doing it again...
Any other information is appreciated.