Hello: My 2009 Mazda5 had a misfire code (301) and an engine check light illuminated. I decided to change the spark plugs and all went good except for water found in the #1 spark plug cavity (cylinder on the left side of the engine near the oil cap) and the spark plug wire connector. I dried the area really well and also the harness connector, replaced the plug and the engine is running fine now. Question is how did the water get into the area and the connector and should I be looking for a water source? Any information will be very much appreciated. The car has about 150K on it and purchased new. Also, at the risk of sounding like a novice (I am), any information or recommendations for replacing the rear brake pads? Thank you for your time and efforts - this is a great forum and all of you are valued.

 

Water or antifreeze? Water cannot get into the cylinder if there is a spark plug in the cylinder and securing tight and then you would have had to either washed your engine compartment or submerged the engine compartment in water.

Did you check after driving a day or so to make sure all the I/M monitors in the ECU are all in state of ready. As well checked for and DTC and also permanent DTC. If not, then you should do that ASAP.

 

I think you’re right about a spill at some point since last spark plug change 2 years ago. It looked like rusted water not antifreeze. Engine runs good now. Thank you for your time .