Hello,

Two weeks ago, I was driving my car on the highway and reached about 80 mph. At that point the engine light comes on and starts flashing. I slowed down and the light was flashing for the duration of the entire trip (which took about 10 minutes) until I got home. There was a significant loss of power, the rpm was oscillating and not stable. Also, pressing the gas pedal was not giving me the expected rpm and power but a lower response. Earlier on that day, there was a message on the display saying "Check Gas Cap". That message came up twice earlier that day. These days have been very cold and we have had snow here. Later that night, I went to Autozone and had the codes read. There was a random misfire code, the P0304 code (misfire on cylinder 4), also a code about the gas cap. I thought the issue was coming from the spark plugs and decided to purchase the Autolite double platinum spark plugs from Autozone. Few days later, I decided to take the spark plug from cylinder 4 out and replaced it with the new one from Autolite.

About 4 months ago, I decided to clean my throttle body since the car was shaking when at ldle. There was some oil accumulated there and it was very dirty. After cleaning the car was fine and no longer shaking, however the rpm at ldle were higher. I attempted to have the ECM relearning the values and it seems the rpm values went back to normal after some time. Also, noticed my gas mileage decreased (higher gas consumption).

Today, I decided to work again on the car since it has been very cold outside the last weeks and decided to check the TB again to see if it was dirty after 4 months of being clean. I exposed the TB and saw that it was pretty dirty again and the most shocking thing for me was that there was a significant amount of oil with a yellow coloration in the plastic piece that connects the air intake (coming from the air filter) to the TB. Also, I saw that there a solid piece inside which was basically a piece of "frozen" liquid. I thought oil itself would not freeze. There were some ice crystals and the entire thing had a yellow color. This junk is coming from the small hose that connects this plastic piece to the engine, since I saw this coloration in that part as well. I decided to clean everything very well using the TB cleaner as well as paper towels to dry the liquid that was in the plastic part. After having everything cleaned and dried I reinstalled everything and decided to go for a ride to see if the car was now fixed. The negative terminal of the battery was also disconnected for like 20 minutes before turning on the car in order to reset any codes. After driving the car for few minutes and when pressing the gas pedal the engine light started flashing again. I drove the car for about 5 miles and returned home. Also checked the codes and the only code that was on was the P0304. At this point, I decided to order the exact spark plugs that came with the Cobalt from factory - the AC Delco 41-981. I will try to install these to see if this will fix the issue. I am also thinking about switching the spark plug installed on cylinder 4 to another cylinder to see if a different cylinder will misfire.

Since I am not a mechanic and not very expert on this condition I would really appreciate if any of you could help me diagnose the issue.

Another thing that I forgot to mention is that the gas exhaust pipe is not releasing the vapors like before. Instead the vapors are being released on an intermittent pace. Like puf-pause-puf-pause-puf. By placing my hand nearby I can feel the intermittent release. Also, I noticed some liquid coming from the exhaust pipe. It is probably gasoline that is not being properly burned due to the misfire. If you want I can make a video or take pictures if that helps.

Thanks a lot for your help.