My wife stopped for gas at a Circle K, about two days later this Sienna started idling rough and missing. I put some Seafoam in it and it cleared up. About one week later, she gets gas again, at another Circle k,about two blocks from the other one. Again, the next day she comes home from work complaining of the van running rough. I took it out and it drove fine. Whenever this happens the Check Engine light comes on, so I ran a code reader on it and it tells me, “Miss detected on cylinder 3”. So I checked all the plug wires, took out the plug (which I had just changed back in Oct.) and checked it, it looked fine. I thought maybe it could be the coil, so I switched the coil to see if I got the same code reading on a different cylinder. I unhooked the battery to clear the code after switching the coils, started it up and still got the rough idle and code. I turned it off (the van) and go in the house, I come back out and start it and it’s running fine. I go to the store and all is well, go inside the store for maybe 45 minutes, come back out and start it up, I get the rough idle and missing.
I ran the code reader on it again and cleared the code, then restarted it and it was running fine again.
Whatever it is, it has something to do with starting the engine (a 3.1L). One time it will start up and drive fine, the next time it starts the rough idling and missing. I figured if it was the coil and I switched them and got the same code on a different cylinder I’d narrow it down, but so far it has been running normally.
Any help or suggestions are greatly appreciated. Thanks.
Cylinder misses are caused by two things. Lack of spark and lack of fuel. If you feel that you have eliminated the spark issue (which I am not so sure you have) then I would check fuel injectors.
Can you confirm that the code is always a cylinder 3 misfire (P0303)? If it is that means one thing. But if it jumps around from cylinder to cylinder or goes to a multiple/random misfire (P0300) that would suggest other things.
If it is ALWAYS cylinder 3 then I would suspect a fuel injector and maybe swap #3 with another.
But in the midst of pulling apart the fuel rail, I’d pull the plugs back out at check the compression - obviously looking to see if cylinder 3 looks much different from the others. So I’d extend the list from bloody_knuckles to four things. To get combustion in there you need gas and air and compression and spark. For a single cylinder misfire that remains with that cylinder the top possibilities are the fuel, spark & compression.
Monday I switched out the coil, cleared the code and restarted the van. Everything was fine until last night, my wife drove it and it started missing again. I ran the code reader on it and am still getting the misfire on cylinder 3. I had checked the plug to see if there were any obvious signs of wear or maybe a burn mark, and the plug looks fine. Why would it be an intermitten miss? I can’t understand why it runs fine, then after restarting it, it starts the missing.
I don’t understand why you don’t understand what was said above about fuel injectors and other stuff. You keep talking about spark plugs and coils.
A misfire code does not tell you that there is a lack of spark. It happens because of a lack of combustion. For combustion to happen in an internal combustion engine you need to have fuel and air enter the cylinder in about the right proportions. The fuel and air have to get compressed by the piston. While its compressed the spark plug has to spark - then it explodes. So a misfire can be cause by a problem with 1) fuel; 2) air; 3) compression; 4) spark.
You’ve got spark covered - move on.
Perhaps the #3 injector is leaking and starts to flood that cylinder. Perhaps the #3 injector is failing electronically and once it heats up fails altogether or goes to intermittent. Perhaps the same applies to the connector for that injector. Perhaps you have a valve issue that only shows up with heat or under certain running conditions - or whatever. Check the compression. Swap the #3 injector with another one.
Well excuse me, I was just relaying what I had already done.
Yes - and you were relaying it while ignoring what had been said to try to help you. You put your fussing with plugs & wires & coils in your initial post. Then you were given other things that you had to worry about, and yet you still just reiterated messing with coil the coil.
So bye. Sorry I tried to help.
So are you telling me I should check the plugs and coils again? I already did that.
From bloody_knuckles post: "If you feel that you have eliminated the spark issue…then I would check fuel injectors. "
From my first post: “If it is ALWAYS cylinder 3 then I would suspect a fuel injector and maybe swap #3 with another…But…I’d pull the plugs back out at check the compression…”
From my second post: "A misfire code does not tell you that there is a lack of spark. It happens because of a lack of combustion. For combustion to happen in an internal combustion engine you need to have fuel and air enter the cylinder in about the right proportions. The fuel and air have to get compressed by the piston. While its compressed the spark plug has to spark - then it explodes. So a misfire can be cause by a problem with 1) fuel; 2) air; 3) compression; 4) spark.</u?
You’ve got spark covered - move on."
In short you had two people telling you to forget the spark and look at any of those other things. For a single cylinder misfire the other most likely things are problem with fuel delivery and/or compression.
So no - I was not telling you to check plugs and coils again. I was saying EXACTLY the opposite.