Hello: Yesterday I posted problems I was having with my truck running like crap, bucking like a bronco, and running super rich, blowing soot out the pipe. The Engine light has been on continuously. Anyway, After working on it today, so far, I have come to an interesting observation. Having removed all spark plugs and wires, I found that the # 5 spark plug on the engine block (from left to right) had rust on the tip of the plug, as well as the inside of the rubber boot of the spark plug wire where it connects to. Also, the wire came off so easily, as if it wasn't even connected. Assuming this wire was not connected properly, could this explain why my truck was running rich, and with the Engine light on? The truck is a 1995 Ford F-150 2 WD 4.9 liter, and it was running fine a couple days ago until the Autozone guy hooked it up to a computer. Anyway, before he hooked it up, the light was intermittently going on and off, and I am thinking that the intermittent light (before Autozone) was a sign that the # 5 plug was intermittently connecting. Anyway, I will keep you posted later today and give you the whole scoop. Since my truck is my only transportation, I have to wait to get a ride to the auto parts store. By the way, there was a lot of soot on all 6 plugs, but all the plugs (except for the 5th one) had no rust on the tips where the wires go, indicating that they were indeed connected to the distributor wires. Steve

 

It won't throw a code for a misfire, so you have at least two problems going on. You definitely need to give it a tune-up and pull the codes to find out what the computer thinks is going on.

 

check air cleaner while you are at it.

 

Hello: This is roller_steve responding to the first party that responded. I did a google search on faulty spark plugs and service engine lights, and a few articles stated that a "Service Engine" light could be triggered on if there is a bad plug or a disconnected one. One article went on to say that not only would the car run rough, but also, you could ruin the catalytic converter as well. I am now wondering if you could destroy the engine and transmission as well, which is possible if you consider the fact that the vehicle is bucking and working hard in order to run on one less plug. Just my comments, that's all. I will keep everyone posted if this cures my problem later tonight once I get to the parts store. Steve

 

That is true for newer vehicles, but your truck is OBD-I and will not throw a code for a misfire.

 

It may throw a code for something else such as an O2 sensor. If one cylinder misfires, that introduces a lot of oxygen into the exhaust stream which is interpreted as a lean mixture. The computer then richens the mixture to compensate for the perceived lean condition. I'm not so sure that this is the problem here or not, but replacing the plugs certainly won't hurt anything.