Today my check engine light came on while the truck was warming up. This is the third time it has come on in the past 3 weeks! The idle is kind of rough, tomorrow i am going to try to clean the IAC to see if it helps at all. The first time the light came on it was a cylinder 8 misfire, i replaced the sparkplugs and that fixed it, the cylinder 8 spark plug was junk, the metal prong at the end completely snaped off. Well, a week later it came on again, brought it back to autozone and came up with the same problem (cylinder 8 misfire) the guy just reset it and the light did not come back on until today. I think it has only comes on when it is at idle, for a few seconds or so the idle will get pretty rough, think that that is when it happens. Today at the roughest part i thought i heard a couple of pings and then the check engine light came on, so i just disconnected the battery for about 10 minutes so it would reset, and i have been driving it around all night and it has not come back on yet. Do you think that the rough idle could have caused this??? Do you think that the rough idle could be because of the IAC??? The two "check engine" lights that i got the code read both said cylinder 8 misfire, so could there be something wrong with the cylinder, checked the spark plug today and it look perfect??? Also, i just recently got the plenum gasket replaced, so could all of the oil and deposits have clogged anything up (like sensors, ect.), should i run any type of cleaner through it???

THANKS

 

I'd do a compression check on that cylinder. Having a spark plug fail in a cylinder is not good at all...those pieces went somewhere, and could have cracked a valve.

 

If the cylinder was stilll misfiring or not firing at all wouldn't the "check engine" light come back on because it hasn't yet???

Thanks

 

I just had the same thing happen to mine while troubleshooting the 02 sensor. "CYL7 Missfire "The truck would stumble and act like it was going to die. My only difference was that at speed the check engine light would flash...This got me really weirded out. Then I remembered what I had done. I washed my truck right before it. Seems that Plug 7 wire had a short to the engine. Mine was a little more obvious then yours but after replacing the plug wires all is good and sounds smoooth. Hope this helps...Look at the plug wires too

 

IF YOUR LIGHT FLASHES YOU SHOULD STOP DRIVING ASAP, COULD CAUSE CAT. DAMAGE.
YOU MIGHT WANT TO LSO CHECK PLUG WIRES AND REPLACE ALL PLUGS, THERE CHEAP. YOU ALSO COULD HAVE A BAD FUEL INJECTOR. SWAPP WITH A GOOD CYLINDER
FOR A QUICK CHECK.

 

Do you just mean when the "check engine" light comes on or actually "flashes".

 

it doesn't flash it just comes on, and when it comes on i think that it only comes on on startup, it idles a little rough. Cleaned is IAC and that did not make it smoother. I am going to compression test it.

 

It may not come on right away. I just went though this with my mothers Ford Aerostar. She put in a set of Bosch +4's and the isolater broke apart on one cylinder. It looked like all the pieces had been caught by the four prongs, yet she had a misfire and the SES light would come on every now and then. I finally got tired of pissing around with it and did a compression test on it. Apparantly some small fragments of the isolator fell into the cylinder and cracked the exhaust valve, and I ended up having to replace the head.

The pieces from your spark plug went into the cylinder, and I'm sure they've caused some damage. Definately do a compression test on that cylinder and let us know the results.

 

RAMTUFF, you said that the whole insulator broke off in your mom's car. In my truck the only thing that broke off was half of the electrode. That could damage a whole head could it, the worst it could do is break a valve right??? I do not see how something that small could break a whole head. It only runs rough on idle, so if there was a cylinder with very low compression wouldn't it make it run rough when you give it gas too, because mine does not???

Thanks

 

"That could damage a whole head could it"

I mean: That couldn't damage a whole head could it???