Outside spark plug red deposit

[mooder]

The spark coil tip has a reddish color and the outside of the spark plug (along with the side inside of the cylinder) are also reddish (rust). The actual tip of the spark plug is ok (maybe a bit black at the base).

Is it because the plug wasn't tightened enough? Cylinder 1 has some, #2 is the worst and #3 & #4 are fine. I got a misfire code for cylinder 4. I did a compression test and got 120 PSI for #1, 3 and 4. Cylinder #2 had the worst result < 90 psi but I managed to obtain once 120 PSI by cleaning a bit the thread. The compression kit that I used is a bit cheap and you can only tighten by hand and I believe the 120 PSI reading to be the maximal pressure the seal can sustain. The cylinder 2 thread is obviously more rusty and the seal is even worse. I also tested with oil inside of the cylinder #2 and I saw no difference.

The car has an exhaust smell coming from the engine bay. Turning on the fan with air from outside will cause the cabin to smell. I had in the past O2 sensor (exhaust) code which I attributed to another problem in the exhaust system (haven't had any in a good 6 months). I have a recurrent and very intermittent problem characterized by the engine wobbling (jittering RPM) at start-up. Pressing the acceleration pedal stalls the engine. Within 1 minute, the engine regime changes and becomes normal (RPM goes up and is steady). This problem arises more frequently when it's cold outside. Until a few days ago, I never had any code showing up after these events. Recently, I had such event and a P0304 code showed up.

I was suggested to check the PCV valve and throttle valve too. Aside I'm still looking for ideas as to what it could be!

[mooder]

I added some pictures of the spark coils. #3 and #4 are alike and don't show anything. The #1 is slightly reddish and #2 is quite apparent.

Car: Yaris 2006 Toyota 218 000 km 1.5 L petrol Hatchback/Canada model.

[flash22]

thats nothing to worry about it just the heat from the engine, if they are cracked that is another issue as the spark will track to the head and may cause a misfire or a weak spark

What spark plugs are in the engine ? (make and model)

Edit. Just took another look at the pic's, coil pack No. 4 looks to have a split boot

[mooder]

2 hours ago, flash22 said:

thats nothing to worry about it just the heat from the engine, if they are cracked that is another issue as the spark will track to the head and may cause a misfire or a weak spark

What spark plugs are in the engine ? (make and model)

Edit. Just took another look at the pic's, coil pack No. 4 looks to have a split boot

The old plug were Denso SK16R11 (Iridium). I changed them maybe 60k kms ago so they were definitely still good.

I'll double check the #4 boot but I didn't anything... Any chance you could edit the picture to show me?

Thanks

[flash22]

looks like you have had lots of water down the spark plug holes 1 or 2 of them are badly corroded the plugs them self looks a good colour

ideally replace them or clean them up very well - on the coils the rubber boots should pull off but watch out for the spring, they may be corroded if its sat in water

[mooder]

9 minutes ago, flash22 said:

looks like you have had lots of water down the spark plug holes 1 or 2 of them are badly corroded the plugs them self looks a good colour

ideally replace them or clean them up very well - on the coils the rubber boots should pull off but watch out for the spring, they may be corroded if its sat in water

That's strange, I don't get how water can get inside for #1-2 but not #3-4... The side of the engine #1-2 is definitely dirtier so that might be due to the design... like an entrance closer which might leave more water accumulating? Also, could it be due to the spark seal being poor? Leaving  some fume from the cylinder inside?

Anyway, either way the cylinder #4 spark and coil seems fine (I'll double check the shoe, also tempted to simply switch the coil if the error code shows again). Any idea what might cause what I'm observing - jittering RPM at startup?

[Madasafish]

It sounds as if you may have a damp problem. When car warms up, damp disappears. I would check under the bonnet drains are not blocked.

[mooder]

1 hour ago, Madasafish said:

It sounds as if you may have a damp problem. When car warms up, damp disappears. I would check under the bonnet drains are not blocked.

Damn thanks this sounds like that's exactly what happened. Hopefully this will fix everything.

If anybody have another idea, please post it! Sort of thing that yaris usually suffer from.

[flash22]

looking at the rust you may have had 30-40mm of water in the plug holes if the end of the coil and plug are wet/damp it will misfire and make it run like a 3 legged donkey

the engine cover should deflect most of the water if fitted

[mooder]

Thank you