Water in spark plug well P0300 code

[Steelworker26]

Having an issue with my 2005 GXP. After not driving the vehicle for about a month I jumped in one a cold day and started the car. The check engine light came on and was flashing.

I took it to O'Reilys and had it read which came back as a P0300 random misfire. I searched this forum for any reference to that code and decided to visually inspect all my coils and plugs.

I have pulled all the front coils, blew compressed air in the spark plug wells to remove any debris which there tended to be enough to be concerning. I visually inspected the coils and saw nothing suspect. I then pulled the plugs and saw all where white which I believe means the car was running hot.

I pulled the back coils off (fun times) and blew compressed air down the spark plug wells. The backs were free of debris but...the second well from the right (not sure of the cylinder #) had water spray out. It looked clear cause it splashed clear on my mirror and it was enough to know it was not from the compressor. It wiped off easily (not sticky/oily like antifreeze).

I am hoping the last time I washed the engine I got water in there indirectly which caused the P0300 code. I am pulling the plugs on the back wall and will replace all plugs.

It's funny, as sealed as the coils seem, there was a lot of debris down in those spark plug wells to make in shudder at the thought.

Will followup tomorrow.

[CMNTMXR57]

There is a little rubber grommet/seal that may not have been replaced or was worn that allowed water down there.

[Steelworker26]

Had the battery checked and it was good, charged it overnight (they said it was needed), finished pulling the plugs, the back ones were different in that they were not white but slightly brown. 3 out of 4 plugs had slight moisture on the threads. I used a hair dryer as best I could to air out the wells, Put new AC Delco plugs in gapped to 0.050, reinstalled the coils and buttoned the car back up and no change in performance. Code is still P0300 random misfire.

I keep going back to the item that the car was running great then it sat for about a month (had a few below freezing days) and now this immediate issue upon startup.

It has a poor idle and upon acceleration on occasion it will clean up and run good as its shifting and then starting out from the next traffic light it will dog and not shift properly like 3 seconds at high RPM then it will shift (like the gas pedal stopped working) with a very long high RPM run before shifting.

The moisture/water in the wells is concerning. And I did not notice any of the coils having a gasket or O ring. They fit snug going down the wells but there was only a hard plastic to metal seal on all of them.


Lastly there is noticable white chalky substance on my back bumper near the exhust. It's acidic in smell. Not sure if I am hoping against hope on it being a manifold gasket issue. Does anyone have another idea on how to trouble shoot the issue? Any help would be greatly appreciated.

[J Wikoff]

Is it using any coolant?

[CMNTMXR57]

Again, I ask if there were any of these rubber grommets around the coil stem, that mounts between the aluminum bracket the coils mount on and the cam cover;

The green "o" ring

[Steelworker26]

Is it using any coolant?

Nothing abnormally as far as I could tell. I had "topped off" the coolant a few weeks before I let the car sit for a month.

[Steelworker26]

Again, I ask if there were any of these rubber grommets around the coil stem, that mounts between the aluminum bracket the coils mount on and the cam cover;

The green "o" ring

I will have to pull and look. I individually removed the coils leaving the aluminum tray in place. I will specifically look tonight.

[Steelworker26]

Took it to a Chevy dealer for an evaluation. They said it passed the head gasket test but they think it is a head gasket issue.
Gave me a $4500 estimate to instal a used motor. I asked if it had the stud insert kit our just standard OEM studs and he said he had no idea but assumed the OEM.


So now I am shopping around for a garage that will just drop the engine for me then re-install.