Last couple days 4R ran rough/missed at start up, then smoothed out after 15 seconds.
- Thread starter Jeff T
- Start date
YotaDriver
New member
Let me clarify myself here: obviously I hope it's the plugs, but following the head gasket issues with the V6 engines pretty closely I'm a little nervous for you. I drive a V6, too and when I swapped out my plugs one of them, the #6 cylinder plug, had more oil on the threads than the others. I haven't had any codes thrown nor have I had any rough idling problems, but I'm always fearful when I hear the terms "check engine light", "misfire", and "rough idle" in a thread about this engine.
The suspect plug is the left-most one in this picture. The sixth plug is still riding around in my skid plate, I assume.
The suspect plug is the left-most one in this picture. The sixth plug is still riding around in my skid plate, I assume.
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Those are the factory plugs I presume since they're half NGK and half Denso. How many miles you got and what year? I don't know if you've seen but there have also been some people that had oil on their plugs that came from a bad o-ring I believe. Can't remember exactly what it was right now but it wasn't the head gasket. Just something else to keep an eye on.
Good stuff. Thanks for posting back the results.
YotaDriver
New member
Yeah, they were the factory plugs and they had almost 90k on them when I swapped them out. I hadn't heard about the o-ring issue but since my truck doesn't lose any coolant I've been doubtful that it's a head gasket issue. I haven't pulled that #6 plug since I changed them to see if there's oil on the threads, but I'm leaning towards a leaking valve cover gasket as the culprit.
OP - glad to hear the new plugs rectified the problem.
That's what I was trying to think of - the valve cover gasket.
Hate to tell you this, but 90% it is the head gasket issue. When engine cools down over night, coolant would leak into the cylinder and slowly fills it, so when you go start the engine, you would have misfire on that cylinder until all the coolant blows out of the tail pipe, the engine would smooth out again. The leak is small enough that would not bother much when the engine is running. The longer you let the engine sits, the more coolant is in the cylinder and the rougher the misfire would be at start-up. If you put a borascope into that cylinder when the engine is cool, you would see coolant dripping from the head gasket. Good luck!
He's started another thread about this:
http://www.toyota-4runner.org/4th-gen-t4rs/119620-need-help-experts-here-regarding-cel.html
Edit: BTW, I'm curious why you just joined and found a 3 week old thread to bump to the top. Were you searching for HG problems to comment on or something?
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