Misfire cylinder 1 and 2 after rain. Replaced spark plugs and ignition coils.

Hello all,

I have a 2010 Toyota Prius II with 242,916 miles on it. At about 240,244 miles, I had a check engine light from cylinder 2 with accompanying codes from cylinder 1 and 4. I cleared the codes and changed the spark plugs and changed the engine air filter. A code came up for cylinder 1. I cleaned the mass air flow sensor. I waited to gather more information on how the car was behaving before doing more work. It stopped raining for several days and the misfires disappeared after a few days. Then it rained and the problems came back. Frustrated, I changed all the ignition coils even for the perfect cylinder 3 and blew out the spark plug wells for good measure. It rained again and I received more misfires. Now I’m putting the old ignition coils back in because I don’t want to damage the new ones. Plus, rust accumulates on the ignition coils. I’ve removed the boots from the old ignition coils and cleaned them with dish soap to remove any residue. I’ve also cleaned the edges of the valve cover holes hoping that creates a better seal.

I’m getting frustrated because I’m worried about my catalytic converters. Hundreds of misfires have occurred while I go through this process. Does anyone have any advice for me? Much appreciated.

• This topic was modified 2 years, 4 months ago by  Kaz Kimura.

Topic

[Richard KirshyParticipant]

Let go over what you know…
1 Cylinders misfires
2 Changed the spark plugs and changed the engine air filter
3 Code came up for cylinder 1
4 Cleaned the mass air flow sensor
5 Stopped raining for several days and the misfires disappeared after a few days
6 Then it rained and the problems came back
7 Changed all the ignition coils, blew out the spark plug wells for good measure
8 It rained again and I received more misfires

Fair to say the issue is moisture being the root cause of your issue not failing or failed ignition component(s)
Willing to suggest your issue is water intrusion in another area.
I would perhaps start looking at the wiring, connectors, connections.
There may be another possibility, that a different component is becoming faulty when exposed to moisture thus affecting the ignition system.
Possibly a cam or crank sensor or associated wiring.
You could try spraying water at a specific area and see when or if it causes a miss fire to narrow your search.

[Kaz KimuraParticipant]

There is rust on all ignition coils and some started to form at the top of the new ignition coils. There is a tiny bit of rust in 2-3 of the spark plug wells. I cleaned the rubber rings for the ignition coils and the 4 rings of the valve cover where they sit. Do you think that will work? I’m assuming water is in there since there is rust. I’m confused as to how water is getting in there. Is it possible that the valve cover gasket needs to be replaced?

[Richard KirshyParticipant]

My first question is (not trying to be a wise a$$)
Are you sure it’s rust and not corona staining?
Another question is this vehicle used for mostly short trips (under 5 – 10 miles) a lot?
If so it is not uncommon for moisture to build up because the engine doesn’t stay running long enough at operating temps to dry out completely.
With the amount of mileage you describe it is possible that the valve cover gasket and spark tube seals my need replacing.

[Kaz KimuraParticipant]

Not at all! I’m just glad to have some help.

I have a video of the spark plug wells. You can see there is some rust. This rust is on the ignition coils. I have not been pulling out the spark plugs.

https://www.dropbox.com/s/xuts5r5uu316b31/Video%20Oct%2027%2C%2010%2025%2001%20AM.mov?dl=0

• This reply was modified 2 years, 4 months ago by  Kaz Kimura.

[Richard KirshyParticipant]

If it is rust formation due to water intrusion from the tops of the coil packs.
That is a pretty easy fix.
After cleaning out all the rust from the spark plug wells and coil packs.
Coat the sealing ring of each coil pack with some silicone grease to create a water resistant seal.
Might also try coating the coil extension tube and a bit inside were it makes contact to the spark plug.
See if that solves the issue.

[Kaz KimuraParticipant]

Okay thanks. I’ll try that. Do you have a method for getting the rust off the ignition coils and inside the spark plug wells? A paper towel and rubbing alcohol don’t seem to be working efficiently.

• This reply was modified 2 years, 4 months ago by  Kaz Kimura.

[Richard KirshyParticipant]

Scotch brite pad

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