Heavy rain, now misfires, CEL

[tommyt]

Heavy rain all day and car misfired - better now since things dried out but the CEL codes that are in the ECU currently are P0300 Random/Multiple Misfire. P0301 Cylinder 1 Misfire and P0303 Cylinder 3 Misfire. The technician checked readings from the Mass Air Flow sensor and Oxygen Sensors during his diagnostics and takes that in account. If the Mass Air Flow was not with in spec. then that would point to some thing wrong with that sensor. Those readings were accurate. Shop wants 1000 for new plugs, coils - seems in line with what other paid but no guarantee that will fix it according to tech.  Given rain I assume coils are bad but we shall see....

[kgoertz]

I'd bet on it being the coil packs.  And even if they weren't the only problem, if they haven't been replaced yet they are probably due.

 

I had a flashing check-engine light after heavy rain storm with misfire codes.  Replaced the coils myself (which were cracked and in very rough shape) and the problem hasn't occurred in 2 years since.

Replacing them yourself isn't that difficult.  The biggest challenge is getting the mufflers out to make it easy to see the coils and plugs.  Apparently it can be done without removing the exhaust but I used the excuse to do the Fister mod on mine.
ECS Tuning sells a kit with 6 Bosch plugs and coils for just over $300.  That's what I used and haven't had any problems since.  And there was a noticeable power increase after replacing them :)

[Uwon]

+1, been there-exactly same symptoms and solution.

Johan