Engine diagnosis (4.7 Toyota)

Joined
Feb 18, 2009
Messages
215
Location
Pennsylvania
2006 Sequoia 154,000 miles. On the way home from work Friday my wife described the start of a tapping noise in the engine and check engine light came on. I had her look for fluids leaking and check the oil. It was a quart low which is odd as I never have to add oil between oil changes every 7500 miles. She also said traction control light was on. She was almost home and I was still at work. She said it ran fine and didn’t notice anything but the tapping noise that would increase with rpm’s. I told her to baby it home. Scanner said misfire in cylinder 5 p0305. I added a little oil and started it in the garage. Heard the tapping noise initially and then it went away. Noticed a lot of blue smoke at back of garage after letting it run maybe 20 seconds. Today I pulled the coil and spark plug and obviously have a major problem. I didn’t pull valve cover yet but any ideas what may have happened? The spark plug was loose and you can see the threads are tore up on it. Did the piston slam into the plug? (See photo)
IMG_1676.webp
 
I see lots of oil coating those parts, are these the kind of plugs that sit down inside the valve cover? If so, probably the seal went out. After that, who knows. It also looks like the ground electrode is gone from that plug. If it ended up in the wrong place I suspect you may have a scored cylinder.
 
Yeah, compression test first probably. Or borescope first if you wanna play around.

Not sure why the plug is broken in two, that's the most concerning. But it's too early to panic yet.
 
Never changed plugs but wish I would have. Might have found that it was loose. Going to get a bore scope and see how things look in the cylinder and maybe find the electrode. If in there might have to try and find a long reach magnet but hoping it got blown out the exhaust. Going to try and use a back thread tool and rethread the hole. Try to keep shavings from falling down in the cylinder. Researched heli coils and time serts but hoping this will work.
 
Why is that spark plug boot eroded and oily looking? I have plugged several V6 ignition modules from the spark plug and it does look like that. Also the white ceramic insulator looks broken.
 
  • Like
Reactions: D60
Owned about 7 years. Had 60k on it and now has 150k. Spark plug was laying loose and assume the boot melted from engine heat coming through the spark plug hole. Would oil leak by the rings (blow by) because of pressure from the engine? Wondering if that is why oil was coated on the plug and bottom of coil.
 
It seems like the engine would run pretty horribly like this. I would at least pull all the plugs.
I don't understand how a plug could "lay loose". Can you thread another plug in?
 
Already pulled valve cover on Sunday. Didn’t find anything amiss but obviously you can’t see in the cylinder. Getting a bore scope to take a look in the cylinder.
 
So that's what a factory fitted spark plug looks like at 157k... Let's see the rest of the lot.
 
Wonder if, after 157k miles that plug got a little loose and tried to hang in there..then the threads got a little sideways, then she blew.
 
I didn't pull the oem plugs out of my 4.7 4runner until 140k, and they were all in there pretty tight. One was too tight and had me worried as I removed it. Makes me wonder if whomever owned it before you was messing with them. It would have to be a super rare occurrence for the plug to loosen on its own, but the heads are aluminum and the plug thread is steel.
 
I didn’t try pulling any other plugs yet but have some Densos ordered. Going to use bore scope to see if something internally broke and pushed plug out. Also want to look for the electrode to plug and try to fish out with flexible magnet. Crossing fingers that the plug worked its way loose and blew out. Here are pictures with valve cover off but need to get bore camera to check internally.

IMG_1695.webp


IMG_1692.webp


IMG_1694.webp


IMG_1693.webp


IMG_1691.webp
 
Back
Top