Misfire on Cyl #6 DTC 3010

[Mike6158]

My LC started running rough this morning. The check engine light comes on but doesn't stay on.

175k. Timing belt and all that was done. Timing belt issues would be way worse than misfiring imho

It's been raining here all week but if it was water in the fuel all cylinders would misfire wouldn't they?

What do I need to troubleshoot, fix, or replace?

Coil pack? Spark plug(s)?

 

[Ninja Cruiser100]

coil would be my guess...

 

[mrbigboy]

Swap a coil pack from #6 to another cylinder and see if the code follows the coil pack. If it does, replace coil.

 

[Mike6158]

Nifty... Is that a replace all 8 thing or replace as they fail?

The weird thing, to me anyway, is that it's throttle position sensitive. The check engine light does not stay on. It runs rough when driving in town but the light stays off most of the time. A little over town speed, say 40mph, and the light comes on for a bit, then goes off. The roughness varies with throttle position. I can "mash on it" and it accelerates as good as it ever has.

 

[Ninja Cruiser100]

Usually when a coil goes bad the car will go into limp mode. Replace them as they fail.

 

[Mike6158]

I drove it home after it started acting up, about 8 miles or so, it didn't go into limp mode. Ever. The check engine light turned on and off a few dozen times as I made my way down some country roads. I could accelerate as if passing someone with no apparent issues. The check engine light didn't come on. It's an odd problem...

 

[Trunk Monkey]

If when it comes on it's flashing, that's to let you know it's an immediate need and you shouldn't really be driving. In the case of a coil pack, since that cylinder is no longer firing, you're dumping fuel through the exhaust and into the hot cats. Not good for them. Won't cause damage immediately, but you don't want to drive around like that for a week.

 

[Mike6158]

It's not flashing. It comes on, I change speed, it kind of smooths out but that could be wishful thinking, and the light goes out. It's obviously running rough prior to and when the light is on. I parked it once I got it home. I had planned to take it on a 400 mile round trip but I take the check engine light on my vehicles seriously. Sometimes it is and sometimes it ain't (serious). I err on the side of caution. Being stranded sucks...

I'm going to check it out more tomorrow. I was behind schedule and had to get everything swapped over so I could get on the road so I pulled the codes, looked at the engine top cover and gave it a hug goodbye.

 

[Mike6158]

Rather than jack around with unlikely things I went to the local parts store and to my amazement they had another coil in stock (just one though). Next question, I vaguely remember seeing that cylinder numbering is different for Toyota than Chevy. Never mind that fact that I haven't had to care about that for 30 or more years. Vehicles have come a long way. So... which cylinder is #6?

 

[Mike6158]

Never mind. I found this:

 

[Mike6158]

Occam's razor- Among competing hypotheses, the one with the fewest assumptions should be selected.
or in simpler terms
If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck

Swapped in a new, non-Toyota coil and cleared the MIL... poof, problem solved