I had just pulled into my driveway and was about to turn off my truck when I noticed it wasn't running quite right. The idle fluctuates between 500rpm and 800rpm and does so pretty roughly. Normal is between 900rpm and 1000rpm. I imediatley turned it off and popped to hood to check for any obvious signs. Sure enough there was a very small amount of smoke coming out from somewhere behind the motor around the 4th cyl. and also around the ground wire at the rear of the motor that connects to the firewall. It feels like it's a misfire but I dont feel any loss of power.

I tested each spark plug cable and they all work fine. I removed the distributor cap and noticed a small bit of carbon build-up on the 4 studs. I've cleaned them with de-greaser and also used some sand paper on them and they look alot better. It ran smoother and idled closer to normal but still runs to rough to say it's safe. I drove it down the street to go to AutoZone to buy a new distributer but when I popped the hood again at the end of the street I noticed that small bit of smoke coming from the back. I turned around and headed back to the house just to be safe. Also checked the oil and it's fine as well.

What else could I check for? Could that smoke be a sign of a cracked manifold? It doesn't tick like a cracked manifold would though. Anyone have some advice? Thanx in advance

Check your oil. Does it have any water beads in it indicating a going head gasket?

I didn't see any when I looked the first time but I'll take a closer look. I now have to drive it to work so hopefully it wont blow on me there.

what color was the smoke? white, blue or black? is the truck an auto or manual? pull the plugs and inspect them, if you have a head gasket going the cyl that is being affected will look different from the others. hopefully that is not what it is.

Yup, I tested the original plugs and everything checked out. No Misfire but sure sounded like one. After I got off work and started it up it ran alot better but not smooth. By time I got to my friends Ford Dealership it was running normal again. There I cleaned the entire motor(first time in a year!) and got rid of alot of grime and grease and oil. Picked up some new plug wires on my way home and it runs better than ever. I can't imagine that the plug wires would just all of a sudden go bad like that? Wierd.

It's a manual btw, and the smoke was white. Not "Blown Head Gasket" kind of white but just white(if that makes sence?). The smoke was also soming from somwhere around the top pf the tranny, not from the ground cable in the rear of the motor. But it's running fine now so I'll let it go and keep an eye on it until it acts up again. Thanx ya'll.